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Sinclair Micromatic Radio Kit (Unbuilt), 1968
For keen collectors of the often bizarre and idiosyncratic electronic gadgets dreamt up by Sir Clive Sinclair during his golden era (late 1950s to early 80s), there are a handful of rare, must-have items. They include his first ever radio kit, the Slimline, the classic Micro FM Receiver, the elusive and ill-fated FM Radio Watch, and this little beauty, the Micromatic radio, but it’s not any old Micromatic…
These tiny matchbox-sized radios are not that uncommon and there's often one or two on ebay, but they are almost always the ready-made models (originally costing 79/6 or £3.98), or the slightly cheaper kit built version. Either way the condition is usually quite poor due to the flimsy plastic cases, and the ravages of time, and the kit models rarely worked. This one, though, is as scarce as the proverbial rocking horse droppings; it has never been built and is as close to mint as it's possible to get. In fact the only signs that it is getting on for 50 years old is a few light creases and scuffed corners on the cardboard box. Everything inside is as the day it was made. The majority of the parts have clearly never been taken out of the polystyrene tray as they're still held in place by the original strips of adhesive tape.
Another sure sign that it has never been touched is the inclusion of a complimentary pack of Ersin Multicore solder – still unopened -- and the Return Slip. This is something a great many buyers (me included) would have used. Micromatics were notoriously fiddly to build; the copper foil on the PCB would crack or peel if you so much as looked at it, let alone touch it with a hot soldering iron, and more often than not they simply didn’t work. I later discovered that a lot of apparent failures were due to Sinclair’s habit of using reject and out of spec transistors, to keep down costs, rather than any lack of skill on the part of the builder.
The adverts gave the impression that it was relatively easy to build but it was actually quite a challenge. Apart from the delicacy of the PCB, which gave you just one chance to mount and solder a component, several parts had to be assembled so carefully that even the slightest mistake would result in it not fitting into the case. The fine windings on the ferrite coil antenna allowed no margin for error and snapped at the lightest touch and aligning the earphone socket so it would fit through the hole in the plastic case required the dexterity of a brain surgeon. Nevertheless, anyone handy with a soldering iron could expect assemble one in couple of hours, and if you were very lucky it might actually work, which felt like quite an achievement.
We’ve looked at the performance and shortcomings of the Micromatic before but it is worth repeating that this little radio uses a very simple two-transistor regenerative receiver circuit. Whilst it will pick up strong AM stations, when fairly close to a transmitter, there’s no volume control. In fact the only control is the tuner dial and plugging and unplugging the earphone switches it on and off. The only way to adjust the sound is to turn the radio orientating it away from the incoming signal. Even though it was very basic they sold in large numbers, thanks in large part to Sinclair’s craftily worded adverts. The radio’s tuning circuit is a classic example. It uses a postage-stamp sized compression trimmer as the tuning capacitor. These devices were only ever meant to make one-off adjustments, and they operate in a non-linear manner. That means when you turned the dial the capacitance varied unevenly and not enough to cover the frequency range of the Medium Wave band in a single turn of the dial. Sinclair turned this around and made it sound like a benefit by claiming the Micromatic had a ‘bandspread’ feature and ‘slow-motion tuning’...
The thin plastic case had a nasty habit of cracking, especially around the earphone socket and eventually the corners of the case would break, due to the tight-fitting sliding back panel. In the end it would get so bad that the back wouldn't stay on. The battery contacts rusted (moisture on the users fingers would do it) or corroded due to leaky button cells, and repeated battery changes would result in the battery contacts detaching from, or cracking, the circuit board. But this was all part of the charm of the Micromatic and these cute little radios gave a generation of kids, of all ages, a proper hands-on introduction to electronics (and faultfinding), and I suspect leading many to a lifelong interest and even careers in technology.
This Micromatic kit is the later Mk II version, introduced in 1968, a year after the Mk I. There are several differences between the two models, including a major redesign of the circuitry. The Mk I used three highly temperamental metal alloy transistors (MATs), these were replaced by two silicon types on the MK II, which had a higher gain, lower noise and were better able to withstand high temperatures, static discharge and incorrect wiring. There was also a welcome reduction in the price of the Mk II kit, down from 59/6 (£2.98) to 49/6 (£2.58). This may not sound a lot but shaving ten shillings off the price made it more affordable for youngsters, and the silicon transistors made it a little easier to build and very slightly increased the chances of it actually working.
I found it on ebay a while ago, at about the time when 60s and 70s vintage Sinclair products were just starting to attract attention (and higher prices). Nothing was missing from the box; it even came with a six-pack of original RM-675 button cells. These have long-since been discontinued and replaced by alkaline and lithium types as they contained toxic mercury (the modern equivalents is the LR44/AG3). Needless to say the old cells are completely dead but remarkably they haven’t leaked. The auction had an early morning, mid-week ending, which often helps to keep the price down by reducing competition from rival bidders. I was pleasantly surprised to see that my opening bid of £20 was successful, and unchallenged. This was a fair bit more than I would normally have paid for a Micromatic (the going rate back then was around £5 – £10) but unbuilt kits were very few and far between so it seemed like a fair price. It could still be assembled and probably made to work but that would be a sacrilege and an expensive mistake as by now it is probably worth several times what I paid for it.
What Happened To It?
There is very little to add to the already well documented history of the Micromatic radio (1967 – 1972) and how this one managed to survive is a mystery but as I recall the seller’s other items for sale suggested that it may have come from old or shop-soiled stock. Nowadays complete unbuilt kits on ebay are very few and far between. Maybe once or twice a year one comes up and when they do bidding is fast and furious and a selling price of £100 or more is not unusual, maybe a little less if there are parts missing or damage. No doubt there are still a few out there, lying forgotten in cupboards, lofts and garages, so there is still a chance of one turning up at a car boot sale for a silly price, in which case do not hesitate, and at all costs resist the temptation to see if it still works!
GIZMO GUIDE (Manual)
First seen 1967
Original Price 49/6 (£2.48)
Value Today £75 - £100 (0816)
Features DIY AM receiver kit, 550 – 1600KHz, 2 transistor (ME4102) regenerative tuner, rotary tuning, ferrite antenna, earphone on/off switch, small coil Ersin Multicore solder
Power req. 2 x RM 675 1.4 volt button cells (modern equivalent LR44/AG3)
Dimensions: 150 x 150 x 28mm (retail box)
Made (assembled) in: England
Hen's Teeth (10 rarest): 9
Sinclair Micro FM Tuner Receiver, 1965
Of the many weird, wonderful and often flawed electronic whizwangs churned out by Sinclair Radionics in the sixties and seventies the Micro FM Tuner Receiver has to be one of the rarest and most desirable of Sir Clive’s radio designs. It was only on sale for a couple of years, between 1965 and 1967, and as was so often the case it was in a class of its own. At that time FM broadcasting was fairly low key and most people did their radio listening on AM (Medium and Long wave) receivers. FM radios were still quite exotic, the majority of them were bulky mains-powered tabletop jobbies, or built into radiograms (early home entertainment systems, which doubled up as ugly pieces of furniture…).
Truly portable FM receivers were few and far between, and none of them were anything like as small as this one. However, what made it really unusual was that it was sold as a kit, which went some way to explaining the price of £5 19 shillings and sixpence, or around £5.97. Even so, the thick end of six quid was a not inconsiderable sum back then and I desperately wanted one, but it was well above the pocket-money pay-grade of a pre-teen like me.
Whilst it looks and behaves like a small portable radio, albeit without a speaker (you had to listen to it though a tinny crystal earpiece), its real purpose in life was to be a tuner for Sinclair’s rapidly expanding range of audio amplifiers and modules. The fact that you had to put it together yourself was not a deterrent though, and in the 1960s if you were interested in audio, being able to solder and dabbling with electronics came with the territory.
Sinclair had a track record with radio kits, going back to the late 1950s with the ultra rare Slimline, followed by the Micro 6 in 1964, but these were very basic super regenerative AM receivers. Essentially they were only a notch up from crystal sets, using just a handful of components and requiring no specialist knowledge or equipment to build or set up. FM radio, on the other hand, is a tad more complicated and the Micro FM is a 7-transistor superhetrodyne design, so at first glance it sounds like a bit of a challenge for the average tinkerer. However, thanks to some clever electronic jiggery-pokery, and something called a pulse counting discriminator, Sinclair managed to do away with a hefty chunk of the circuitry (the IF stage), which is the part with several coils that require careful adjustment, so, in theory at least it should have been virtually alignment-free.
Other familiar Sinclair traits include an almost complete absence of controls, in fact there’s only one, the tuning dial. To switch it on you plug in the earpiece and to adjust the volume… Well there isn’t a volume control, but you could tweak it by moving the radio or shortening the telescopic antenna. Those of you with good eyesight may have spotted another trademark Sinclair cost and space-saving feature. It’s the tuning capacitor, which like previous Sinclair designs re-purposes a component called a trimmer, which was designed to make one-off adjustments. Needless to say it wasn’t particularly well suited to this sort of application but somehow Sinclair managed to get it to work, and got away with it. The transistors used in this design are also old friends. They are early germanium types, and as usual they were out of spec rejects, bought cheaply in bulk from manufacturers and re-graded by Clive Sinclair and his family and staff to work with circuits designed around the semiconductor’s particular characteristics. One other feature that deserves a mention is the case. It is a larger version of the one used for the Micro 6, and the later Micromatic radio, with a sliding back panel. These are made of a wafer-thin plastic, which has a tendency to crack around stress points (earpieces sockets etc), and in Sinclair’s quest to make it as small as possible, fitting everything into the tiny fragile box without breaking it was no mean feat.
Nowadays Micro FM Receivers are rarer than the proverbial hen’s teeth with perhaps only two or three coming up on ebay each year, and when they do they tend to be fought over and sell for eye watering amounts. I wasn’t very optimistic when I spotted this one, though I almost missed it as the photographs and description were a little vague and didn’t really do it justice. Anticipating that it would sell for at least £100 I didn’t bother bidding, but a few days later and by sheer chance, I spotted that the auction had about 5 minutes to go. I was amazed to see that it still had just the opening bid, which suggested that it was all going to kick off in the last 30 seconds. Twenty seconds from the end I couldn’t resist a speculative bid of £25, and for some reason that I still do not understand there was only one more half-hearted bid in the last few seconds and it was mine for £20.00.
It turned out to be an abandoned project, a complete kit, still in its original box with instructions but with just one transistor to fit and the final wiring and assembly left to do. After a lot of thought I have decided not to attempt to finish it off. I seriously doubt that it would work first time, and troubleshooting would be a nightmare. Sinclair printed circuit boards are famously fragile and the thin copper traces do not tolerate de-soldering. The PP5 9 volt batteries it uses are no longer made, though it is possible to cobble something together using button cells, but preserving it in its unfinished state means that there’s no risk of damage. It will now remain in near pristine and original condition. Even if it did work the performance would be disappointing and whilst the simplified circuitry meant it could be built by comparative novices, it would be highly unstable and not much fun to actually use. It wouldn’t stand up to much handling either and I seem to remember that a lot of them failed if pressure was put on the telescopic antenna, which would snap a large chunk off the case.
What Happened To It?
Although the Micro FM only remained in production for two or three years during that time such was the popularity of Sinclair kits that it probably sold reasonably well. Parts of the circuitry resurfaced a year or two later and formed the basis of a matching tuner for Sinclair’s stylish System 2000 amplifier. Initially the tuner was mono only and an add-on stereo adaptor had to be devised but this ran into problems and eventually a purpose-designed stereo tuner was developed.
By the end of the 1960s pocket radios with FM coverage were becoming increasingly common, and falling rapidly in price; by then Sinclair was getting more involved in mid-range hi-fi, pocket TVs and starting to dabble with watches and calculators.
The flimsy and fragile case, the difficulty of getting one to work and suspect performance meant that it was unlikely that many Micro FMs survived beyond then end of the decade. This one, which probably spent most of the past 50 years lying untouched in its box, may well be one of the cleanest examples around. The few that turn up on ebay tend to be unboxed and in a pretty poor state, yet in spite of that they can still sell for £100 or more. A complete unbuilt kit would probably fetch a small fortune. Needless to say this one, which I waited so long to own, isn’t going to end up on ebay anytime soon, though eccentric millionaires are welcome to make me an offer…
GIZMO GUIDE (Manual)
First seen 1965
Original Price £5 19s 6d (£5.97)
Value Today £100 (0815)
Features 7-transistor superhetrodyne mono FM tuner (87.5 – 108MHz), pulse counting discriminator, AFC, 2 x 2.5mm mono jack outputs (high-impedance crystal earpiece & external amplifier), 5-section, 370mm telescopic antenna, crystal earpiece. Quoted current consumption 5mA, sensitivity 3uV, audio output 300mV into 25k ohm.
Power req. 1 x PP5 9V battery
Dimensions: 75 x 43 x 23mm
Made (assembled) in: England
Hen's Teeth (10 rarest): 8
Sinclair Micro–6 Matchbox Radio, 1964
Like so many of the gadgets featured on these pages the Sinclair Micro 6 was something that I hankered after as kid, but could not afford, and by the time that I could it had disappeared.
The Micro 6 was the second of Clive Sinclair’s matchbox radios. The first, the Slimline was sold as a kit and as far as I can see it wasn’t around for very long.
The Micro-6, which first appeared in 1964 was based on a similar circuit design and used the same high performance metal alloy transistors (MAT) as the Slimline. Legend has it that Sinclair used to buy up batches of rejects which he graded and used in his kits and ready made radios. As always with Sinclair products the sales blurb was enticing and nothing if not inventive. This included the claim that it was the ‘world’s smallest radio set’, in spite of the fact that at least one Japanese radio of the time was smaller and considerably more sophisticated. But that didn’t matter, it was tiny, relatively inexpensive, it looked great and I wanted one!
The 6 in the name is another example of Sinclair’s bold way with words and alludes to the circuit having ‘six stages’. Theoretically it does but the simple three-transistor design only achieves that by some technical jiggery-pokery, known as regeneration, which basically involves re-using parts of the circuit twice.
The tuned radio frequency (TRF) circuit is actually quite sensitive, but not very stable and stations come and go, depending on how you hold the radio. Other notable features include the clever use of a postage stamp trimmer for the tuning. It's clever because a trimmer -- a preset variable capacitor -- was only ever designed to make one-off adjustments.
There’s only one control, the tuning dial, and the radio is switched on when the chunky crystal earpiece is plugged in. Power comes from a pair of button cells, which last for 4 or 5 hours of continuous use. It’s housed in a small plastic box with a removable sliding back.
It really is no larger than a matchbox, but in order to get it that small the plastic has to be very thin and it is prone to cracking, especially around the earphone socket; very few can have survived without at least one of the corners being knocked off.
The radio was sold as a kit, and ready built, and for an extra 7/6 (37 pence) you could have an optional wrist strap – called the ‘Transrista’ --, making it arguably one of the first, if not the first wristwatch radios.
What Happened to It?
The Micro 6 was sold from 1964 to 1967 when it was replaced by the Sinclair Micromatic. First generation Micromatics were essentially Micro-6s with a fancy new black case, sturdier battery contacts and some minor tweaks to the circuit. Soon afterwards a Mk 2 version appeared, with a more stable circuit employing two silicon transistors and the crystal earpiece was replaced by a smaller magnetic type. The Micromatic lasted until 1971 by which time it was beginning to look a bit past its sell by date, as were the claims that it was still the world’s smallest radio.
My Micro 6 came from good old ebay a few years ago and it cost me £15.00. They do turn up from time to time but it’s been a while since I’ve seen one going for less than £50 and they can go as high as £100, so I’m definitely hanging on to mine. It’s in excellent condition, the case is intact and yes, it actually works. The front panel and dial label looked a bit tatty but I managed to get some decent scans from them and with a little digital magic, made new ones by laser printing on clear acetate film and backing that with gold and black spray paint. I have to say that it looks great and is virtually indistinguishable from the originals, though I’ve kept them safe so it can be fully restored should I ever feel the urge.
First seen: 1964
Original Price 59/6 (£2.47)
Value Today? £50 0311
Features: 3 transistor, 6-stage TRF AM receiver, earphone activated on/off switch, rotary tuner dial
Power req. 2 x 1.2 volt button cells
Dimensions: 34 x 45 x 13mm
Made in: UK
Hen's Teeth (10 rarest): 9
Sinclair Micromatic AM Radio MK 1 & 2, 1967
Few mass produced radios from the 1960s promised so much and delivered so little, but I, like countless other school-age kids, and no doubt a fair few dads as well, were happy to part with two or three pounds for a Sinclair Micromatic, enticingly advertised as the ‘world’s smallest radio’ (needless to say it wasn’t, and later on this was changed to ‘Britain’s smallest radio…).
Who could fail to be impressed by it? The Micromatic looks superb, especially when pictured next to a matchbox and the fancily worded technical spec made it sound vastly more sophisticated that it actually was. Terms like ‘multi stage’, ‘powerful AGC’ and ‘bandspread at higher frequencies’ were bandied about and the flummery extended to the cosmetics. What appear to be holes beneath the tuning dial turn out to be blanks, but they clearly suggest that it has a built-in speaker. It doesn’t, of course, and to maintain the illusion it was never shown alongside the companion earpiece.
The fact is the Micromatic is a very basic 2 or 3 transistor AM radio – more on the differences in a moment – based around a simple superegenerative tuning circuit, which is essentially one step up from a crystal set. The circuit was pared to the bone, highly unstable and one of the reasons it is so small is that the tuning capacitor is actually a compression trimmer, designed for one-off adjustments and not well suited to this application; it was also the reason for the impressive sounding (but pointless) ‘bandspread at higher frequencies’ feature, which was actually due to the trimmer’s non-linear characteristics.
Clive Sinclair’s marketing budget must have been huge, with ads, for this and his other electronic products and modules, often running over three or four pages in most of the monthly radio and electronics enthusiast magazines; it also made regular appearances in general interest magazines and newspapers. The Micromatic was available ready built, or for a pound or so less, you could assemble one yourself from a kit, and that is what most of us did. It is impossible to say now how many of those kits actually worked first time. My guess it was fewer than half of them, but to Sinclair’s credit, they could be sent back and fixed, sometimes for free if it hadn’t been too badly botched.
The Micromatic went through several revisions during the 4 or 5 years it was on sale but they can be boiled down to the relatively rare Mark 1, and much more common Mark 2 versions. The Mark 1 was essentially a cosmetic re-hash of the earlier Micro 6 and used an almost identical 3-transistor circuit, employing MAT (metal alloy transistors). At the time these were amongst the most advanced transistors available, with high gain and low current consumption, but they were incredibly delicate and would self-destruct if you so much as looked at them. The Mk 1 is characterised by a square-cornered case, the earphone socket is on the left side and doubles up as the on/off switch, when the earphone plugged in. It came with a piezo (crystal) earpiece and uses two tiny ZM312 mercury button cells.
The Mk 2 is an even simpler design, and this time the case has rounded edges. It uses two silicon transistors (ME102 or D1425), which have higher gain and are a lot more robust. The earphone socket is on the right side of the case, it uses a marginally better sounding magnetic type earpiece and is powered by slightly larger RM675 button cells. Incidentally, whilst the original mercury cells these radios used are no longer made (mercury is toxic), several near-equivalent and slightly less toxic alkaline button cells are still readily available.
Both models suffered from numerous and often critical design flaws; here are just a few of them. The most serious one is the flimsy battery contacts. These are made of thin tin strips, soldered directly to the copper foil on the printed circuit board. The adhesive holding the foil in place is instantly weakened as soon as the soldering iron is applied, no matter how quick you are, and it will tear or detach after only a few battery insertions. Even if it didn’t fail straight away sweat from funbling fingers or leaky cells would cause them to corrode and the contacts become intermittent in a matter of months. The ferrite antenna and tuning coil is held in place by thin strip of glue. This eventually weakens as the coil brushes against the sliding battery cover; whern, inevitably, it works loose, one or more of the fine coil wires will break. The case is made of a thin and extremely brittle plastic that will not survive even a short drop onto a hard surface. It will often crack around the earphone socket, for no good reason, and the corners and edges are weak and chip easily. The sliding case back rarely stays in place and unless it is removed and inserted very carefully the grooves it slides in break off.
Now don’t get me wrong, I was and still am a huge fan of this super-cute, but horribly flawed little radio. As a youngster I saved my pocket money and wages from a paper delivery round and over a period of a couple of years purchased two kits. I only managed to get one of them to work, blaming it on my own lack of skill rather than poor design or faulty components. Years later I learned that Clive Sinclair used low grade and reject transistors in many of his kits so I reckon he still owes me at least 49/6. But I forgive him, and will continue to acquire them, when the price is right, and I currently have five complete ones – all runners -- plus a fair assortment of parts from terminal basket cases.
There is not much to say about performance, if you are very close to a strong AM transmitter you might hear something, briefly, but move it, or touch it and it will drift off station with the least provocation. In short, as a radio it’s not much fun to listen to, but that’s not what it’s about. For all of its shortcomings, and it has many of them, it has bags of character. It was British to its bones, and in spite of the liberties Sinclair took with the electronics and marketing spin there is no denying that it is tiny, great fun to build and for a lot of people, an introduction and for some the start of a lifelong interest in electronics.
What Happened To It?
Sadly the Micromatic was the last of Sinclair’s kit radios and it seems likely that he was put off making any more by the high return rate, which must have made them relatively uneconomical. Ads for the little radio had stopped appearing by 1972, though production probably wound up a year or two earlier and the last ones were almost certainly old stock. By then it was well past its sell-by date, in fact it was pretty much outdated even before it went on sale with smaller and more sophisticated radios coming out of Japan and Hong Kong several years earlier. To be fair the Micromatic was quite cheap, and the kit version was undoubtedly very popular.
Prices on ebay vary dramatically. Junkers are fairly common and usually sell for £10 - £15, depending on the condition. Clean examples that work can go for anywhere between £20 and £50, but the ultimate collectible for Sinclair fans is an unbuilt kit. These are extremely rare and when they do come up, can easily fetch £100 - £150 when they are complete and in mint condition.
First seen 1967
Original Price kit 59/6 (£2.97), ready built 79/6 (£3.97)
Value Today £10 - £50 0614
Features AM receiver, 550 – 1600KHz, 2/3 transistor regenerative tuner, rotary tuning, ferrite antenna, earphone on/off switch
Power req. 2 x 1.3v button cell (modern equiv. Mk1: AG3, Mk 2: AG12
Dimensions: 45 x 33 x 16mm
Weight: Mk1 27.3g, Mk2 25.6g
Made (assembled) in: England
Hen's Teeth (10 rarest): 4
Sinclair X1 Button FM Radio, 1997
You can’t keep a good inventor down, and at one of the lowest points in his career, serial miniature radio designer and electric vehicle pioneer, Sir Clive Sinclair, came up with this little gem. Back in 1997 Sinclair’s various enterprises were struggling to survive with mounting losses, but never one to give up, Sinclair Research – by now virtually a one-man band -- announced the X1 Button FM radio. I will have to dig out the ads of the day but I am fairly certain Sinclair reprised claims made for a previous generation of minature radios and billed it as the ‘world’s smallest’. It was priced at £9.50 and it was indeed tiny, just 30mm across. It almost certainly wasn’t a record breaker but to put it into perspective it is only slightly larger – in diameter – than a 2 pence coin. The idea was that it was worn or rather hung on the ear, by a springy detachable plastic clip (for left or right ear use), with a foam-cushioned earpiece pressed against the user’s ear canal.
Cramming an FM radio into such a small space would have been quite a feat, were it not for the development of a new generation of single chip FM tuners (Philips TDA 7088), which as in the past, Sinclair was quick to exploit. He has a track record in this area and Sir Clive’s early mini radios (Micro 6 and Micromatic) were amongst the first to use new fangled transistors, and he regularly beat the big boys to market in the 70s and 80s, utilising new components and being one of the first to launch a pocket calculator, digital watch, wristwatch radio, personal computer, pocket TV and even electric vehicles. Interestingly he has been threatening to revive the X1 name with a new wacky electric two-wheeler, though true to form, the planned launch date was supposed to be 2012 and at the time of writing (spring 2013) it had yet to appear.
Titchy FM radios are two a penny nowadays, well, 99p in our local bargain store, but it was definitely a novelty in 1997. It looked impressively teccy, thanks to clever cosmetics, but the reality was it was a fairly basic design. There are only three controls, an on/off switch and a pair of buttons, one for scanning up the FM band (88 – 108MHz), the other to reset the scan. FM receivers need good aerials and Sinclair’s solution was simple, though not especially elegant, a 900mm length of thin black wire, which dangles from the underside of the receiver. On the plus side it was quite effective and reception of the main stations was pretty good, even in fringe areas. The main drawback is the lack of a volume control; it’s all or nothing, and it’s not that loud. It goes without saying that the quality is pretty dire, but for listening to the news or a talk station, say, in quiet surroundings, it’s not too bad. The scan tuning is also okay, once you get used to it, though if you miss a station it’s a bit of a pain as you have to keep on scanning or reset and start over, and if the station is weak, or you are moving it can be difficult to stay tuned.
Another unusual feature is the power source. It runs on a single CR 2032 3-volt button cell. It was claimed that this could last up to a year, which was probably true if you never switched it on, but you would certainly have got a several weeks and maybe a month or three out of one, with moderate use. I seem to remember that these cells were quite expensive back in 1997, costing up to half as much as the radio, though nowadays you can buy a card full of them at your local pound store.
Now we come to a bit of a mystery, where was it made? Previously most Sinclair products were built in the UK, by subcontractors, like Timex and Thorn EMI, but there are no tell-tales or marks on this one. The circuit board uses surface mount components – still a little unusual in 1997 -- but the quality of assembly is surprisingly poor, it looks almost hand built, so my guess – and I am happy to be proved wrong – is that it’s Chinese in origin (they’ve got a lot better since then…), though I wouldn’t be surprised to learn that it was locally made, so if anyone knows, please let me know.
What Happened To It?
I have no actual dates but I am fairly sure the X1 was on sale for at least 3 years, though this may simply have been a single production run and overly optimistic predictions. However, two years after launch Sinclair Research came up with yet another micro radio, the Z1. This was even smaller than the X1 and got around the troublesome wire aerial by being an AM only receiver – but that’s another story for another day.
If memory serves the Z1 was also around for two or three years but it is not that common, maybe one or two a month turn up on ebay. Occasionally there’s a tussle between two keen bidders and the price gets pushed up to £20 or more but typically they sell for between £5 and £10.
I was sent one to review when it first came out and I recall getting some strange looks whilst wearing it (at least I think it was the radio…). Nowadays you probably wouldn’t get a second glance with half the population wandering around with garish Bluetooth earpieces stuck in their ears. I have no idea what happened to it but over the years I have bought a couple of X1s, probably costing no more than £3 or 4 and they are still in great condition and good working order. The original foam earpiece cover crumbled to dust long ago but modern earphones covers are a near perfect fit. In design terms it’s not especially significant and there was a Japanese hang-on-the-ear radio at least decade earlier, but it’s a must-have for Sinclair fans and a cosy reminder of the days when little radios were still a bit of a novelty.
First seen 1997
Original Price £9.50
Value Today £9.50 0313
Features 88 – 108MHz mono FM, scan tuning, on/off, scan & reset buttons, external antenna (wire)
Power req. 1 x CR2032 3v button cell
Dimensions: 30 x 25mm
Made in: China?
Hen's Teeth (10 rarest): 6
Sinclair Research Z-1 Micro AM In-Ear Radio, 1999
The Sinclair Research Z-1 is not quite the craziest product from the incredibly fertile mind of Sir Clive, but it’s not far off… It’s a tiny radio and like the wonderful Micro 6 and Micromatic radios from almost 40 years previously, it was ambitiously (and still erroneously) billed as the ‘world’s smallest’. Fair’s fair, it is tiny, you might even say it’s an early example of wearable technology, designed to fit in the users ear, a bit like a Bluetooth earpiece. The only problem was, for many people, it wouldn’t stay there and had the unfortunate habit of dropping out unless you held it in, but more on its multiple shortcomings in a moment.
Technically it is quite clever. It’s an AM only receiver based around a single chip tuner, driving an integral earphone capsule via a simple one-transistor amplifier. There are only two controls, a rotary tuning knob on the back and an on/off slider switch on the side. There’s a space-age flexible wire antenna coming out of the top; it’s powered by a single 1.3 volt SR44 button cell, with a claimed running time of 40 hours. It came with its own smart lozenge shaped carry case and it was very attractively packaged, and priced.
All up weight, including the battery is just 8.5g, which doesn’t sound a lot but the only way it is going to stay in place is if the earphone is firmly wedged into the user’s ear canal, (or the antenna gets tangled up in your hair). There is a thin foam cushion on the earpiece, but it has diameter of the earpiece is 15mm, which I suspect is a fair bit bigger than most people’s ear-holes so even if you manage to cram it in, after a few minutes it becomes incredibly uncomfortable. Incidentally, the foam cover turns to dust after a few years but replacements are very widely available, so it’s not a problem for purist collectors.
Now we come to the performance. In short it doesn’t work very well, in fact it’s terrible, and unless you are within spitting distance of the transmitter you won’t hear much besides medium wave mush and buzz. It may not have been too bad back in the late 90s, when a fair number of powerful AM stations were broadcasting, but nowadays you would be very lucky indeed to find anything to listen to. The tuner also happens to be rather touchy and just moving your head slightly, or putting your hand to it – to stop it falling out – makes it drift, and it doesn’t have any sort of volume control, apart from moving your head. Suffice it to say the Z-1 was probably not the best choice for anyone who actually wanted to listen to the radio, but credit where it is due, it does look cute with its little aerial, the selling price of £9.95 wasn’t outrageous and it probably did quite well as a gadget geek’s stocking filler.
What Happened To It?
The Z-1 went on sale in May 1999, just two years after the slightly larger and more sophisticated X1 Button FM Radio. I have been unable to find out how many Z-1s were made or when production stopped but as I recall a few years later they were being sold for only two or three pounds. My guess is that it didn't hang around for very long, even though it was quite widely promoted. However, at first it was only sold by mail order, through Sinclair Research, which by then had become a small holding company, following the break-up of his once fantastically successful computer business, which fell into steep decline in the mid to late eighties. It is hard to say if it was a success or not but it has the distinction of being the last in a long line of very unusual and often innovative Sinclair radios
Over the years several Z-1s have passed through my hands, I am fairly sure one was sent to me for review when it first came out but it probably got dropped or pinched soon afterwards. Later, when they were being sold off cheaply, I purchased several for emergency Christmas and birthday presents. This was probably one of them and I found it at the back of a drawer, sadly minus its case and packaging, which would undoubtedly add to its value. They used to be fairly common on ebay and rarely sold for more than £5 to £10 but there are fewer of them nowadays and I wouldn’t mind betting that good examples, in their original packaging, could start to attract some serious bids, so if there’s a Sinclair Z-1 sized gap in your miniature radio collection, don’t wait too long to fill it.
First seen 1999
Original Price £9.95
Value Today £5 0614
Features AM receiver, Medium Wave coverage 530 – 1600KHz, single chip (1GS) tuner, rotary tuning, integral earphone, on/off switch, flexible antenna, 40-hour battery life
Power req. SR44 1.3v button cell
Dimensions: 30 x 20 x 25mm (antenna 65mm)
Made (assembled) in: China?
Hen's Teeth (10 rarest): 5
The Micro Television MTV1A was undoubtedly one of the best things Sinclair ever made. Even after more than 40 years no other pocket TV has come close to what this little box of tricks can do, or is ever likely to now, thanks to the Internet and the global shift towards digital broadcasting.
So what makes it so special? Well quite simply this tiny telly could be used in more than 100 countries. It was genuinely portable too and ran on its own internal re-chargeable batteries. Back in 1976 that was a remarkable feat for something about the size of a thick paperback book and given the diversity of TV systems and standards in use around the world.
It was the culmination of Clive Sinclair’s long held ambition to build a pocket TV. He began teasing us with promises of a titchy telly with a 2-inch screen in the mid 60s. It seemed that it was always just about to go on sale, and at one point it was even advertised with a price tag of 49 guineas. Alas, Sinclair’s enthusiasm exceeded his company’s ability to mass-produce such a device and it never went much beyond the prototype stage. Then in 1976 the MTV1 appeared and it blew everyone away.
Until then Sinclair products had a reputation for been cleverly designed but poorly made but the MTV1 was a revelation. It is based around 2-inch cathode ray tube (CRT) made by Telefunken, originally designed for use in test instruments. It’s housed in a metal case and inside there are 5 densely populated circuit boards, mostly by discrete components but there’s a sprinkling of analogue microchips in the audio and tuning sections. The standard of construction is excellent, though Sinclair made a big mistake with the rechargeable batteries. There are four AA-sized nicads permanently soldered to the power supply board. These would have had a fairly short useful life, 2 –3 years at best, and the only way to replace them was to take the whole thing apart. This is not an easy job, and getting it back together is even harder… A lot of old batteries eventually leak, the corrosive juice eats into the nearby circuitry and many MTV1s effectively self-destruct after 10 – 15 years.
On the positive side it’s very easy to use. The row of buttons along the bottom edge switch it on and select the band and TV system. There are two thumbwheels for tuning and volume and around the back there are four adjustments for brightness, contrast, line and frame hold. It has two on-board antennas, a telescopic jobby for VHF reception and a weird folding frame aerial for UHF channels. There’s also connections for an external aerial, a 2.5mm jack for an earphone and two DC input sockets for mains adaptors. The original outfit came with a range of adaptors that were supposed to work anywhere in the world.
With a good signal the black and white picture can be bright, crisp and pin-sharp, and it comes with a little clip-on sun shield so it can be used outdoors in bright conditions. The circuitry can be a little unstable at times, or after it has been on for a while and getting a decent picture with a less than perfect signal can involve a lot of knob-twiddling and aerial wiggling. The sound is a tad tinny but there’s plenty of volume from the small 45mm speaker, which lives in the top of the case. One other design flaw is the lack of a stand; hand-holding it for more than a few minutes is hard work and getting the right angle and distance makes it a pain to use for longer viewing sessions. But hey, no more nit-picking, this is a pocket multi-system TV from the 1970s, and that deserves respect!
What Happened To It?
Unfortunately it cost a small fortune to manufacture and it almost crippled Sinclair. At one point the UK government had to pitch in with a £1.6m grant and this was reflected in the selling price. Initially it was deemed too expensive for the UK market and the only place you could get one was in the US, where it was sold for a hefty $400 (around £250).
Well-heeled world-travelling gadget geeks were apparently in short supply in the late 70s, consequently the demand for such a device was relatively small and sales were disappointing. At the end of its 2-year production run more than 12,000 MTV1s remained unsold and were disposed of at a fraction of their original cost, resulting in a huge losses for Sinclair. In 1978 the company tried to open up the market with a cheaper single standard pocket TV, called the MTV1B, but this also struggled and the huge costs involved in developing pocket TVs contributed to the company’s eventual downfall and sell-off in 1979.
The MTV1 in the picture is my fourth working example and a recent acquisition. I found it at a Brighton flea market and the stallholder was asking £50 for it. That would be a very fair price for a runner, but he was unable to give any assurances and eventually settled on £35. Even if it didn’t work it was worth that much for spares and as a bonus it came with a case, adaptor, the clip on screen – these always get lost – earphone and instructions, and cosmetically it looked very tidy. The plastic at the top of the screen surround had cracked but this was a well-known design fault and I’ve only ever come across one MTV1 that didn’t have that crack. The only concern I had was that the label on the bottom of the case was intact, which meant it hadn’t been opened (normally a good sign and that it hasn't been fiddled with), but in this case it meant that it probably still had the original re-chargeable batteries inside.
Once I got it home I gingerly powered it up and there was sound but the screen had just a single bright line – it’s called frame collapse. This was essentially good news suggesting that the bulk of the circuitry was intact and working. After opening it up I found that the original batteries were indeed still in place and they had seeped, but only for a short time as the damage was confined to a few tracks on the printed circuit board. Once the batteries had been removed (but not replaced – I don’t want it to happen again) and the chassis reassembled I tried it again and mysteriously the frame collapse fault had righted itself. The screen burst into life and a wobbly picture appeared and I was the happy owner of a working MTV1.
This was an unusually lucky find, but they are out there if you look and there’s a couple of dozen each year on ebay, selling for anything between £50 and £250 depending on the condition and accessories. Sadly they’ve lost a lot of their kudos following the switch to digital TV but they can still be hooked up to analogue sources like old VCRs, DVD players, computers and TV games so they won’t be totally useless. Nevertheless, I suspect that prices won’t go much higher so they’re not much of an investment but don’t let that put you off. It’s a real slice of television and technology history, and a really nice thing to have, even if there’s not much to watch on it anymore…
GIZMO GUIDE (Manual)
First seen: 1976
Original Price £250 ($400)
Value Today? £150 1211
Features: 2-inch black and white CRT, Multi standard VHF/UHF tuner Bands 1 (50 – 90MHz), 3 (170 – 220MHz), 4 & 5 (470 – 890MHz), CCIR Systems B, G, H, I, M, 525/625 lines. Mode selectors, tuning, volume, brightness, contrast, frame & Line hold controls, telescopic VHF and foldable frame UHF antennas, external antenna, earphone socket, 45mm (1.75-in) internal speaker
Power req. Internal re-chargeable batteries
6/12VDC external adaptor
Dimensions: 160 x 104 x 42 mm
Made in: Britain
Hen's Teeth (10 rarest): 7
Sinclair MTV1B Microvision Pocket TV, 1978
Of all the pocket TVs developed by Sinclair Radionics – and there have been a fair few of them over the years -- the MTV1B Microvision stands out as one of the most refined, and least likely to go wrong. That’s high praise indeed, as any Sinclair fan will tell you! This was the second of his tiny tellies, or rather, the second to actually go into production. There was at least one Microvision prototype, and almost certainly several others, developed between Sinclair’s incredibly optimistic announcement in 1965, of his intention to market a pocket TV, and the appearance of the first one, the MTV1A, in 1976.
Although there are a few outward similarities between the MTV1A and MTV1B – they both used the same miniature Telefunken cathode ray picture tube (CRT) and are roughly the same size -- internally, and in terms of features, they are like chalk and cheese. The MTV1A is a full bloodied, metal-cased, multi-standard model, capable of working in more than 100 countries around the world, whilst the MTV1B is a simple, UHF only receiver with just two controls (on/off volume & tuning), and housed in an all plastic case. The MTV1B was almost certainly a response to disappointing sales of the MTV1, which was just too expensive and specialised for the cash-strapped 70s. Sinclair clearly believed that what the market really wanted, and needed, was a cheap and cheerful pocket TV, and that’s more or less what we got, but sadly, once again sales were well below expectations.
It was a real shame because it was basically a good product, and unusually, it actually worked. The price, at £99.99 was a tad on the high side but at the time there was nothing to compare it with. The only real drawback was a thirst for batteries. It uses four AA cells, which live in a compartment to the right of the screen and it could suck the juice out of a set of Duracells in under an hour, which made the mains adaptor an absolute necessity. The comfortable viewing distance is under half a metre but picture quality – with a good signal – was pin sharp and there’s plenty of volume, for private listening from the built-in 34mm speaker. Clever design touches include a folding stand on the base, with three height settings. It could be connected to an external antenna using a pair of screw contacts on the back. There are also preset controls for line and frame hold, which helps to stabilise the picture in weak signal conditions.
Sinclair’s engineers put a lot of effort into simplifying the electronics, making good use of microchips, which were still something of a novelty in consumer products in the late 70s. I am pretty sure this helped to improve reliability too, which was always a bit of an adventure with Sinclair’s products. Several versions were made; the MTV1C was produced for the US market and the MTV1D was configured for European TV systems. At around the same time a tunerless model, the MON1A was developed for use as a monitor; however, this was based on the MTV1A chassis and is now very rare indeed.
What Happened To It?
Production of the MTV1B under the auspices of Sinclair Radionics only lasted for a couple of years. The company, which had already suffered serious losses through this and other ventures, had been bailed out by the National Enterprise Board and by 1978 it was close to bankruptcy. Clive Sinclair left the company and a year later the remaining stocks and rights to the MTV1B were sold to Binatone and although a few sets bearing the new name were made, it pretty much sank without trace.
I reviewed both MTV1A and B several times for various magazines when they first launched and it seems as though I always had one or two of them kicking around in the loft. Over the years I have acquired quite a collection of these little tellies. In spite of poor sales quite a few survived and during the 90s I often came across sad and lonely specimens in markets and car boot sales, usually selling for £10.00 or less. This was about the time LCD pocket TVs started to appear and the bulky – by comparison -- Sinclair design looked decidedly old fashioned.
They still turn up from time to time on ebay, and briefly, between around 2003 and 2008, prices went absolutely mad with top-notch examples selling for up to £100. However, since then prices have tumbled, to between £20 and £50 for a decent-looking runner.
This sudden fall from favour was almost entirely due to the switch to digital TV broadcasting, which rendered this and most other analogue TVs virtually useless. Of course they can still be connected to VCRs and video games with RF outputs, but the real charm of these little tellies was their portability, which is somehow lost when they have to be wired up to other boxes. I’m not complaining though, it just means there’s more of them for me, and my cunning plan to corner the market, when they bring back analogue TV…
First seen 1978
Original Price £100
Value Today £20 - £50 0313
Features 45mm (1.75-inch) monochrome CRT picture tube, single standard (CCIR System 1) UHF tuning, 9-section telescopic antenna (fully extended 610mm), volume on/off & tuning controls, line and frame hold presets, external antenna connection, audio out (3.5mm jack) external power socket, collapsible stand
Power req. 4 x AA cell175 x 85 x 53mm
Dimensions: 30 x 25mm
Made in: UK
Hen's Teeth (10 rarest): 5
Sinclair FTV1/TV80 Slat Screen TV, 1983
Timing is everything in the fast paced world of consumer electronics. Gadgets and fads can come in and go out of date in an alarmingly short space of time and it’s something Sir Clive Sinclair knows only too well. Many of his products, like the first calculator and ZX computers were timed to perfection, but sometimes he got it horribly wrong, and the FTV1 flat screen pocket TV (also known as the TV80) was a case in point. It was out of date even before they started rolling off the production line.
Flat screen video displays were rare in the early 80s but everyone knew they were coming. Casio, Hitachi, Panasonic and Seiko, to name just a few, had been regularly demonstrating prototype screens at trade shows and press events. These were all based on liquid crystal display technology (LCD), which by then was well established on watches and calculators. The only question was who would be first to get a flat screen TV into the shops. It was a close run thing but it was almost certainly Casio, in June 1983 with the TV-10, with several other manufacturers hard on their heels. Four months later Clive Sinclair, as was, announced the FTV1 pocket flat screen TV. This was most definitely not a me-too product, though, and it was typical of Sinclair to defy convention with a flat display screen that owed more to old school 19th century physics than late 20th century microchip wizardry.
It was a clever variant of the cathode ray tube (CRT). Basically it’s a valve, a glass tube with all of the air sucked out where a stream of electrons is fired from a ‘gun’ towards a phosphor screen that glows brightly when struck by the beam. The beam can be moved around the screen using magnetic fields or electrostatic charges, and by varying the brightness of the beam, and scanning the beam across and down the screen 50 times a second it is possible to build up a sequences of still pictures that create an illusion of movement. The big difference with the FTV1 tube is that the screen is at right angles to the electron gun, and it is viewed through the sidewall of the flattened glass tube. Electrons from the gun are deflected down onto the screen by an electrostatic charge. The actual phosphor screen is quite small, just 38 x 18mm, and apparently the wrong aspect ratio (16:9 instead of 4:3) but the image is magnified and the distortion corrected by a fresnel lens moulded in the viewing window in the case. It produces a sharp and bright image, but like all CRTs it’s still a fragile glass bottle that needs a lot of high voltages in order to make it work, which makes packing one into a small box that you can fit into your pocket quite a challenge.
The FTV1 was the result of collaboration with several other companies. Much of the key tuning, picture processing and tube driver circuitry is packed into a single microchip developed jointly with Ferranti. The designers overcame the not inconsiderable problem of powering it by using a weird and wonderful flat battery, originally developed by Polaroid for use in instant camera film cartridges. The P500 Lithium Power Pack did indeed manage to pack a lot of power into a small space, but they were expensive (3 for £10), and didn’t last anything like the 15 hours claimed in the marketing guff. Timex in Scotland handled manufacture of the FTV1 tube and Thorn EMI assembled the parts at their Enfield plant. It was priced realistically at just under £80 (that’s where the alternative TV80 name came from, allegedly…). Most who saw it in action commented favourably on picture and sound quality but it wasn’t enough to for it to fly. Sinclair predicted that production would eventually reach 10,000 units a month, rising to a million a year when it went worldwide but there were serious production delays and according to several reputable sources only around 15,000 were ever built.
What Happened To It?
Two things conspired against the FTV1. Slick-looking Japanese LCD pocket TVs had a clear technical edge and a lot more kudos, compared with the rather dull looking FTV1 and this was in spite of first generation LCD TVs being more expensive and having quite poor picture quality. The second problem was the initial production delays, rumoured to be due to high rejection rates, and the subsequent limited availability, leaving the door open for the Japanese. Production limped on for a year or so but, sadly, it was doomed.
I have half a dozen FTV1s, bought mostly from ebay a few years ago were they were selling for £5.00 or less. There are still a fair few of on sale each month though nowadays good ones tend to fetch £20 or more. Mine still work, though there’s nothing much to see since the UK digital TV switchover. You can bodge up a connection to the aerial from a VCR or TV game but it’s not much fun. Power is also a problem, it will work on a mains adaptor but the wacky flat battery is no longer made. I did once manage to extract something very similar from a Polaroid disposable flat torch and graft it into an expired P500 pack, and it worked, but only for a few minutes. No doubt in time they will become harder to find and prices will go up but it’s unlikely ever to excite much interest outside of the handful of members of the Sinclair products and mini TV collector communities...
First seen 1983
Original Price £79.95
Value Today £10 0513
Features 47mm (2-inch) monochrome flat-screen CRT display, 625-line UHC (chans 21 – 68) coverage, telescopic antenna, 23mm speaker, volume on/off & tuning controls, earphone jack (mono 3.5mm), external DV power socket, fold out table stand
Power req. P500 6-volt flat lithium battery pack & optional AC adaptor
Dimensions: 140 x 85 x 33mm
Made in: UK
Hen's Teeth (10 rarest): 5
Sinclair Black Watch, 1975
The Black watch was the first of Clive Sinclair’s forays into the world of digital timekeeping and another ground breaking product, being the first, and as far as I am aware, the only DIY digital watch kit. This was back in 1975, when digital watches were still rare, exotic and very expensive. At the time the kit cost £17.95; a ready-built version was also available for £25.95, which was a tidy sum thirty and a bit years ago
It’s a really stylish design with no visible controls, or display for that matter, you have to press two barely visible circular pads on the panels, just below the display window to fire up the tiny LEDs. This helps to prolong battery life, even so most users, checking the time 4 or 5 times a day would need to change them every week or two.
It gets worse; the four-digit display only shows the time, (hours, minutes and seconds) though a time and date version was produced. The metal strap is quite well made but the rest of the case is rather fragile and it marks easily. It also has a tendency to self destruct, so all in all it was up to Sinclair’s usual standards…
What Happened to it?
It was a huge flop, the kit was virtually impossible to build, even for those experienced with a soldering iron. The electronics are based around two printed circuits, one of which is flexible and prone to fracture. The push button contacts are incredibly unreliable, but even when it was working it was inaccurate and gained or lost, according to the ambient temperature. The clock chip was easily damaged by static discharge; some users even claimed it would blow if you wore a nylon shirt. It ate batteries and if you dropped it, it flew apart. Tens of thousands of Black Watches were made but the return rate was very high and it was a financial disaster.
Working examples of the Black Watch turn up on ebay from time to time but alas this one no longer functions. It didn’t cost very much -- £15 at an antiques fair -- and I reckon that was pushing it. Runners especially if they are in good condition and boxed, can easily fetch £100 or more.
It’s not quite the end of the story and in 1985 Sinclair went on to make an outlandish and, for its day, technically advanced combined watch and FM radio. Several thousand were made but most of them were destroyed in a warehouse fire shortly before it was due to go on sale in the US. These are now incredibly rare and when they do turn up on ebay they invariably sell for between £300 and £500, and I have seen them going for as much as £800.
First seen: 1975
Original Price £26.00
Value Today? £26.00 1011
Features: Time display (hours, minutes and seconds), two-button operation, wrist strap
Power req. 2 x 1.2 volt button cells
Dimensions: 28 x 50 x 10mm (case, excuding strap)
Made in: England
Hen’s Teeth (10 rarest): 8
Back in the early 1960s Clive Sinclair had the bright idea of attaching one of his tiny radios (the Micro-6) to a strap so it could be worn on the wrist. His early radios were notoriously insensitive and unreliable and needless to say the idea never caught on but the notion of wearing technology on the wrist clearly stayed with Sir Clive and in 1975 he pioneered one of the first digital watches. Later, in 1984, he asked Dagfinn Aksnes, a Senior Product Designer at Sinclair Research, to begin work on a combined LCD watch and FM radio. The full story behind this remarkably innovative product can be found here.
For years it was thought that the watch was just another one of Sir Clive’s experimental products that he regularly floated to the media but rarely saw the light of day. This one was different, though, it actually went into production in 1985 and was close to going on sale when a mysterious warehouse fire in the US destroyed almost all of the 11,000 watches made and the project was shelved.
The fire and the fact that the watch never officially went on sale has made it one of the rarest Sinclair products there is so I was delighted to have finally got my hands on one, and best of all, it actually works.
One of the biggest surprises, if you have only ever seen it in pictures, is how small and neat and it is. The second surprise for Sinclair aficionados is the unexpectedly high build quality. Many Sinclair products fall apart if you so much as look at them but this one is a real piece of craftsmanship, I would like to say it’s built to last but sadly some of the materials used are doomed to deteriorate, but more on that after the guided tour.
The watch is in three parts held together by a tough hinge that wraps around the wrist. The lower module contains the 3-function LCD clock (time/date/alarm) and its battery. It’s fairly unremarkable and the tiny screen is barely visible but it is backlit and the knob on the side switches between loud and soft alarm and radio. The speaker and amplifier module are in the middle and contain a tiny moving coil speaker; the knob on the side controls the volume. Last but not least is the FM tuner and this houses a clever tuning device – see Dagfinn Aksnes’s write up for more details. Suffice it say it’s ingenious but like many Sinclair innovations, not necessarily built to last and it appears to be a common cause of failure on the few watches that come up for sale. Between each section there’s a set of rubber bellows, to keep out dust and moisture, and running between the sections and inside the strap, acting as the aerial there’s a flexible printed circuit, which was quite a novelty back then. The button cell for powering the radio is held in the strap clasp. Tiny circuit boards inside the case make use of another pioneering technology, surface mount components and all in all it is a truly impressive feat of miniaturisation and it looks pretty smart too.
What Happened To It?
A combination of the warehouse fire and financial problems almost certainly put paid to the watch, at least that’s the official version. However, reading between the lines on the various stories that have appeared there may well have been other factors at work. But whatever the reason for its demise, it was a bit of an oddity and unlikely to have sold in large numbers. I reckon that there were three basic problems. First performance; decent FM reception is only possible within sight of a transmitter and for obvious reasons the sound quality is poor and it's not especially loud. To be fair it was originally designed for the US market, where FM stations tend to be a lot more powerful, but even so it would still be quite difficult to listen to comfortably without clamping it to your ear. Second, the watch element is far too small and at the time ‘proper’ digital watches with shed-loads of functions were selling for just a few pounds. The third reason, I suspect, would have been the price. It was never officially announced but my guess is that whatever it was, it would have been too expensive for the cash-strapped mid-eighties, if the costs of the hand assembly and high quality materials were to be recovered.
If it had made it into the wild I think there would have been a lot of returns. Parts, like the strap and bellows wouldn’t have aged well, especially in a humid atmosphere or wrapped around a sweaty wrist and would probably have failed within a few months and clever though it was the flexible printed circuit was just asking for trouble. Fortunately my one, which I bought a while ago on ebay for £85 (a very good price, probably as the auction ended late on a Wednesday morning…) has been very well looked after and here are no signs yet of decay. I can’t say for sure but I doubt that more than a couple of hundred FM Radio Watches survived and judging by the ones that turn up on ebay from time to time, most of those are dead, missing parts or in an advanced state of decay. If you ever come across one, and it’s in decent condition, and the price isn’t too steep, it could turn out to be a very worthwhile investment.
First seen: 1985
Original Price £?
Value Today? £100 - £800 1112
Features: 3-function (time/date/alarm) LCD watch with built-in FM radio and loudspeaker
Power req. 2 x 1.3v button cells
Dimensions: 65 x 22 x 10mm (ex strap)
Made in: Great Britain
Hen's Teeth (10 rarest): 9
Sinclair Z-30 Amplifier, 1969
Magazine adverts and specs for Sinclair products always made interesting reading and I suspect that a lot of it would be outlawed today for the often highly optimistic claims. But you have to hand it to Sir Clive, his electronic designs were never dull, the ads always seemed plausible, and even though you just knew it was going to end in tears, he persuaded lots of people, including me, to part with their money.
The 25 watts RMS output sounded just too good to be true (it was) and the idiosyncratic circuit pushed the components to the limits. It was prone to overheating and thermal runaway, there was no short circuit protection and some said that the only thing it did really well was blowing output transistors. Seasoned users quickly learned to replace the stock components with something more robust.
The Z-30 was actually one of Sinclair’s more successful forays into the audio market. It was part of the self-assembly Project 60 system, which appeared between 1969 and 1970. The idea was that you could put together a high-performance system using ready-made modules, for a fraction of the price of comparable off-the-shelf components. In addition to the Z-30 and the later, more powerful Z-50 amps there was the Stereo 60 pre-amp, an Active Filter unit, PZ series power supplies, a Stereo FM tuner and the now extremely rare Q-16 loudspeakers. All you needed was a soldering iron and some basic carpentry and metal bashing skills, to wire up the modules and construct a housing, and you were in business.
Needless to say it never quite lived up to the flowery promises, which included ‘worlds lowest distortion Hi-Fi amplifier’, ‘laboratory standard’ and ‘perfection that could not be bettered in its class, no matter how much you spent’... The actuality was that in addition to the transistor zapping Z-30s, the pre-amp had a reputation for poor reliability, and lots of crackle, due to the use of cheap trimmers, instead of proper potentiometers for the volume, tone and balance controls. The performance figures for the Z-30 were another area of contention. The power output of 25 watts RMS was, apparently, theoretically achievable, but anyone driving one at full tilt, at the maximum recommended supply voltage would quickly regret it. To be fair if the amps were run at a lower voltage and not put under too much strain, the notorious Active Filter Unit omitted from the system, the linear trim pots replaced with proper logarithmic potentiometers, and coupled to a set of decent speakers, it didn’t sound too bad; there are even rumours of Z-30 based systems still in daily use.
I managed to destroy at least two Z-30s back in the day and although I cottoned on to the trick of replacing the output trannies with some beefy power transistors and more substantial heat sinks, none of them lasted. I found this one in a box of electronic bits and pieces at a car boot sale a year or two ago and the whole lot cost £5.00. It is one of the earliest versions with the extra fragile MP8112 output transistors. They measure OK on my multimeter but I haven’t the courage to power it up to see if it still works; it would be a shame to blow them now, after all these years.
What Happened To It?
The Z-30 went through several revisions, mostly around the output stage, but it was superseded by the more powerful, but equally touchy Z-50 in 1970. Sinclair obviously made a lot of Z-30s, though, and they were still being advertised for sale in electronics mags as late as 1974. Project 60 was phased out and replaced by Project 605 in 1972, which continued the home-build theme. Audio products remained in the company’s line up until the late 70s but by then Sinclair’s was concentrating on digital electronics and the age of calculators, watches and computers had begun.
You don’t have to look very far to find Z-30s and Z-50s, they appear fairly regularly on ebay, though inevitably there are fewer of them coming up for sale as the years go by. Prices hold up well, and good examples often go for £15 to £20, more if sold in pairs, or with other Project 60 modules, and prepare to dig even deeper if they are in working condition and come with any sort of original packing or documentation. Sinclair products can be a good investment, and assembling a complete Project 60 system, with some Q-16 speakers would be an interesting, and possibly quite lucrative challenge.
First seen 1969
Original Price £4.47 (89/6 or £4 9s 6d)
Value Today £20 0214
Features Power output 25 watts RMS (30W peak) into 8 ohms, frequency response 30 – 300kHz +/- 1db, input sensitivity 250mV into 100k, distortion 0.025, Class AB output, 9 transistors (2 x MP8112 2 x ME4102, 2 x ME4101, 2 x ME 0411, ME6102)
Power req. 8 – 35VDC
Dimensions: 75 x 55 x 12mm
Made (assembled) in: UK?
Hen's Teeth (10 rarest): 8
Sinclair System 2000 Mk 2 Stereo Amplifier, 1970
Whilst Clive Sinclair is mostly known for his often innovative, frequently quirky and sometimes downright wacky gadgets, it’s easy to forget that in amongst the world’s first, smallest or cheapest radios, pocket TVs, electronic watches, calculators and computers there were a few mainstream products. System 2000 certainly qualifies as one of them; it was an integrated hi-fi system, comprising matching amplifier, FM tuner and speakers. It was a reasonably determined attempt to break into the middle ranks of the growing Hi-Fi market, which at that time was dominated by a small handful of established brands. Sinclair had already dabbled with audio systems, producing a succession of amplifier modules, but these were mainly aimed at hobbyists, prepared to find or make their own enclosures and do a bit of soldering; System 2000 was built and ready to use straight out of the box, but as usual the advertising puff promised rather more than was delivered.
System 2000 was billed as a 35-watt stereo amp, but omitted to specify what sort of watts they were, or that it was 35-watts in total, i.e. 17.5-watts per channel. The practical reality was the output, on a good day with the wind in the right direction, and assuming it was working, was probably closer to 8 -10 watts rms per channel. There were contemporary reports – perfectly normal for Sinclair products -- of faults and failures on first use. The power output transistors and push-button switches appear to have been unusually delicate and there were some mixed performance reviews, though to be fair most of them centred on the quirky FM tuner. On the plus side, the sleek aluminium case and crisp, minimalist cosmetics were ten years ahead of their time; for the most part the styling of late sixties audio equipment was still grimly stuck in the 1950s. The electronics were cutting edge, using advanced circuitry – especially in the tuner – and a new generation of silicon transistors operating at or close to their design limits, which may also help explain the higher than normal failure rate.
This System 2000 amp came from ebay, it was labelled as non-working but in good shape, apart from some discolouration on the knobs. There was obviously something good on telly that day because there were only two bids, and my rival can’t have been very interested as it cost me just £15.00. I have seen non-runners selling for as much as £50 in the past. The mains fuse had blown so after replacing it, checking for shorts and finding none, I was pleasantly surprised to find out that it was working. The volume and balance pots were a bit scratchy, despite a generous application of switch cleaner, so they would have to be replaced eventually. However, I take the blown fuse as a warning, didn’t leave it powered up for long and won’t be bothering it with mains voltages very often. Apart from anything else it’s too much like hard work to hook up as it uses now virtually defunct DIN connectors for the inputs and speaker connections and finding and wiring up DIN plugs is not my idea of fun.
What Happened To It?
The System 2000 featured here is the later Mk 2 version, probably dating from 1970 or 71. As far as I can make out the main difference between the Mk 1 and 2 is the use of BD187 power output transistors, bolted to a heavy duty heat sink on the inside of the case. These seem to have replaced a set of big all-metal TO-3 types, screwed to the back panel. Unfortunately there’s not much in the way of documentation on this product, but looking through the Sinclair ads in electronics magazines of the day (Practical Electronics and Practical Wireless), it seems that System 2000 disappeared from view in early 1973, to be briefly replaced by System 3000, after which Sinclair moved back to home-build products, with Project 60 modules and the IC10 and IC12 integrated circuit audio amps.
Complete System 2000’s can command very respectable prices from collectors, particular if they come with the original circular speakers. When they do come up ebay, which is probably no more than a couple of times a year, they can go for several hundred pounds. Separate component prices vary a lot and most of the one’s I’ve seen are sold as not working. Putting together a working system is going to take a fair amount of patience and effort. It’s certainly not worth pursuing if you’re looking for a high quality hi-fi system, it’s soundly beaten on almost every level by one of today’s cheapie audio systems, but like almost all Sinclair products from the 60s and 70s, performance is not a consideration, though you really had to be there to appreciate what that means…
First seen 1968
Original Price 29 guineas (£31.48)
Value Today £25 - £50 0813
Features 22-transistor stereo amplifier, 10-watts rms per channel, low-cut filter, bass, treble, balance volume, 2 x line level and 2 x phono inputs (5-pin DINs), switched mains out
Power req. 120/240 VAC
Dimensions: 305 x 180 x 52mm
Made in: England
Hen's Teeth (10 rarest): 7
Sinclair Super IC-12 Amplifier, 1971
These weird looking objects represent another one of Sir Clive Sinclair’s adventures in microelectronics. They’re Super IC-12s, integrated circuit mono audio amplifiers, launched in 1971, with a claimed power output of 8 watts RMS. Whether or not any of them lasted long enough to achieve anything like that is open to debate. In fact the IC12 was Sinclair’s second chip-based amplifier, the first being the groundbreaking IC-10 from 1968. This was almost certainly one of the first IC audio amps available to the public. Unfortunately it had a dreadful reputation for reliability but in spite of that it lasted for a couple of years.
Sinclair didn’t actually manufacture these chips; the IC-10 was made by Plessey whilst the IC-12 was a more sophisticated product from US-based Texas Instruments, and I suspect one of its SN760 series chips, which were used in the audio output stages of TVs of the same era.
The wacky ‘hedgehog’ shape is all down to the finned aluminium heat sink mounted on top of the resin-encapsulated chip, and the reason it’s there is because it gets hot, really hot! Without the heat sink it would probably burn out in under a minute – which they tended to do anyway. To be fair modern microchips also get hot and hard-working ones like computer CPUs need a lot of elaborate cooling, but the IC-12 goes back to the early days of microchips, when heat generation was much more of a issue, and built-in protection and current limitation was a lot less refined.
Back then selling microchips on their own was an odd thing to do. Those early chips were temperamental and fragile, both electrically and mechanically. Sinclair provided designs for circuits, but it invited experimentation and even experienced electronics enthusiasts had accidents so the failure rate was probably very high. To Sinclair’s credit there was a no-fuss guarantee and zapped IC-12s were usually promptly replaced, without question.
What Happened To It?
I can’t be sure how long the IC-12 lasted but it was probably no more than two or three years. The high casualty rate must have been a real problem for Sinclair, though it was rumoured that, like the transistors used in his early radios, these were factory rejects or out of spec items. Nevertheless, the basic problem, then as now, was always going to be heat dissipation. ICs are not well suited to high current applications like power amplifiers and just can’t handle direct to speaker outputs of more than a few watts. By the early 70s the demand for cheaper and more powerful home Hi-Fis had outstripped the capabilities of microchips in the output stages of amplifiers in favour of better performing and more reliable power transistors.
These two were sent to me as replacements after falling afoul of my cack-handed attempts at a home-brew amp. Looking back I suspect there may have been a short circuit somewhere and the use of ‘near-enough’ spares box components was just asking for trouble so they were probably doomed. However, I recall that even if you got everything right they tended to lead rather short lives. I clearly lost interest in getting them to work because they ended up in a box of old ICs and components that I came upon recently in my loft.
I have no idea what they are worth; they do turn up on ebay every so often but they either remain unsold or go for just a few pounds, not much more than the original selling price of £2.98. Being the first of its kind the IC-10 might be worth a few bob, as would be an IC-12 in its original packaging However, the problem with these, and most vintage chips is that they are nondescript and pretty much useless on their own. There’s no easy way of telling if they have popped and there are very few products that used them, so there’s no replacement or spares market to speak of. It’s probably not a collectable, at least not in the foreseeable and unlikely ever to gain much in value but I’m hanging on to mine just for that weird and wonderful shape.
First seen: 1971
Original Price £2.98
Value Today? £5.00
Features: 8 watts RMS monolithic integrated circuit amplifier, 5Hz – 100kHz frequency range, 1% THD, 3 – 15 ohm impedance, 90dB gain, 8mA quiescent current (28 volts)
Power req. 6 – 28 volts
Dimensions: 24 x 45 x 30mm
Made in: USA?
Hen's Teeth (10 rarest): 6
Sinclair ZX 81 Home Computer, 1981
No website concerned with vintage technology would be complete without a Sinclair computer. I thought long and hard about which one to feature and as you know there were several highly influential models. It all began with the pioneering ZX80 and of course who can forget the massively popular Spectrum. There were others, including the Sinclair designed Cambridge Z88, and the sadly forgotten QL, but in my opinion the one that actually made a difference was the ZX81.
Launched in 1981 it was the successor to the ZX80. It sold as a kit for a fairly affordable £49.95, or you could buy one ready assembled – always a good idea with Sinclair stuff – for £70. For that you got a Zilog 80 based machine running at 3.25Mz, 32 x 24 graphic display and with 1 kilobyte of RAM as standard, expandable to 56kb. It’s easy to mock but unless you were there and this was your first real computer, you would be genuinely surprised how much you can do with such a small amount of memory. Anyway, like the ZX80 it was housed in a compact case, not much larger than a paperback book, with a membrane keyboard that users quickly grew to hate. Every key had at least four functions and toggling between them called for a considerable amount of physical and mental dexterity, especially when it came to manually entering lines of BASIC, but for those who enjoyed a challenge it was a real learning experience. It’s no exaggeration to say this little machine helped create a generation of talented programmers.
There’s no need for to go into details about the machine’s capabilities, much has been written about this little computer and its strange and funny ways, suffice it to say that most owners used it to play games, and that was the key to its success, there were hundreds, if not thousands to choose from. What’s more almost anyone determined to put in a few hours and master the intricacies of Sinclair BASIC could write their own games or simple applications, I even managed to run off a few myself, a couple of which I was really proud of, but that’s a story for another day.
It was very easy to set up. It came with a mains adaptor and the built-in RF modulator meant it could connect to the aerial socket of any TV. If you wanted to load or store a program, all you needed was simple cassette recorder. There was even a printer, a dreadful design that used sparks to burn marks on silver aluminised paper; as I recall they cost a fortune to run and lasted about five minutes…
What Happened to It?
More than one and half million ZX80s were sold in the UK making it the most popular home computer of its time. It sold well in the US too, where Timex, who made the UK model, had its own production plant. There were also a number of clones and copies but its popularity was relatively short lived. These were frantic times and Sinclair, like everyone else in the computer business was desperate to stay ahead of the game. And so in 1982, barely a year after the appearance of the ZX81 Sinclair launched the ZX Spectrum with its faster processor, bigger memory, colour graphics and almost useable keyboard. It was an instant hit and sales of the ZX81 rapidly fell off.
I honestly can’t remember where this ZX81 came from. Back in the day I had several that over time either stopped working, or I gave away. I’m fairly sure this was one of the earliest ones and it’s a bog-standard 1kb model, nothing special, apart from the fact that it still works. I fired it up recently, probably for the first time in more than 10 years and was astonished at how much Sinclair BASIC I remembered and how enjoyable it was to write simple programs. It also reminded me of how many hours I wasted entering code from magazine listings for buggy programs that never worked.
Boxed, working ZX80s are quite rare and you are unlikely to find one for under £100; later Spectrums are plentiful and you shouldn’t have to pay more for than £5 - £10 for one at the moment. The ZX81 sits somewhere in the middle and it’s my top tip for a future collectable. Prices are still relatively low; you’ll often see them on ebay, in junk shops and at car boot sales selling for under £20, but probably not for much longer. If you want one go for a pristine example, preferably boxed with a full set of manuals and it’s worth getting hold of any accessories you come across as they are becoming increasingly scarce.
First seen: 1981
Original Price £50 (kit), £70 (assembled)
Value Today? £15 - £30 1011
Features: Z80A Microprocessor 3.25MHz, 1K RAM, expandable to 16K, 32K or 56K, 8K ROM containing BASIC, 32x24 text, 64x48 graphics
Power req. 9VDC (external mains adaptor)
Dimensions: 170 x 165 x 44mm
Made in: UK
Hen's Teeth (10 rarest): 4
Cambridge Z88 Notebook Computer 1987
In the world of computing the current flavours of the month are tablet PCs and small notebooks, or ‘netbooks’. They save space and weight by using solid-state memory and plug-in memory modules instead of a hard drive. They mostly run specialised operating systems (proprietary versions of Linux) that load quickly and some come bundled with office software suites or apps and usually manage to run for several hours, between charges.
What goes around comes around and over twenty years ago Sir Clive Sinclair launched a compact notebook PC, called the Cambridge Z88. It had an A4 footprint, weighed less than 1kg, came with a suite of office applications, used solid state memory instead of a hard drive, data and software are stored on plug-in memory expansion modules, it comes on more or less instantly and runs for a whopping 20 hours on a set of standard 4AA batteries
Okay, so some things have improved and the Z88 screen is a touch narrow. In fact it can only display 8-lines of text, though you would be surprised how easy it is to use for routine tasks like word processing, though it could be difficult to read in some lighting conditions. Otherwise it really is quite civilised; the rubber keyboard is actually very good and there’s a proper serial port so it can communicate with other PCs, printers and modems.
The Z88 had a chequered history. The original idea, back in the early 1980s was to develop a portable version of the hugely popular Spectrum, but by the mid 80s this had evolved into a portable computer called Pandora, which then, after a number of revisions became the Z88. But by that time Sinclair Research was in dire financial straits, thanks largely to the ill-fated C5 electric vehicle and the computer division was sold to Amstrad. In 1986 Clive Sinclair formed Cambridge Computers and the Z88 was finally unveiled to the press in February 1987.
It was an instant hit and I bought this very one soon after the launch for the not inconsiderable sum of £300 (I also bought several EPROM memory modules and an UV ‘eraser’ device, so they could be re-used). This machine proved ideal for press trips and I must have wrote hundreds of articles on it during long flights and sleepless nights in distant hotel rooms. It has probably been around the world several times and it never failed me once. Much to my astonishment after lying dormant in my loft for at least 10 years, it powered up first time!
What Happened To It?
Production finally came to an end in 1989 but in that relatively short time thousands were sold and believe it or not, there is a hardy band of enthusiasts still using them. Over the years there’s been a steady stream of software and hardware upgrades but by the late 80s Cambridge Computers was in trouble again, the company was sold and Sir Clive turned his attention to electrically powered bikes. Without further development it was doomed and in any case the Z88 was being overtaken by portable and laptop PCs that by then were becoming smaller, and cheaper, and more capable. Nevertheless it would take until the late 90s before really small computers, like the Toshiba Libretto, came anywhere near matching the Z88 for size, weight and portability.
First seen: 1987
Original Price £230
Value Today? £50 1210
Features: Zilog Z80 processor, 128kb ROM, 32kb static RAM, (expandable to 3.5Mb), ‘OZ’ operating system, Pipedream word processor/spreadsheet, database, diary, calendar, calculator, alarm, file manager, data terminal, print manager, BASIC, 640 x 64 pixel LCD display, built in speaker
Power req. 4 x AA cell (mains adaptor supplied)
Dimensions: 293 x 207 x 24 mm
Made in: England
Hen's Teeth (10 rarest): 6
Sinclair Cambridge Calculator, 1974 (Manual)
It’s impossible to overstate the impact electronic calculators had on us all back in the 1970s, until that point if you wanted to do a complex calculation, and by that I mean anything that didn’t involve the times tables, you had to resort to fearful things called Logarithms, master the intricacies of the mechanical slide rule, be employed in an office or very well off and own an adding machine.
Although adding machines and later calculators had been around long before Clive Sinclair got in on the act, few could afford them, let alone lift them… The Sinclair Cambridge was the first affordable pocket calculator, though it’s debatable how many ordinary folks could afford to lash out £43 on one of these gizmos, equivalent to several hundred pounds in today’s money. Kit versions were also available, though I seem to remember they didn’t hang around for very long since like most Sinclair DIY kits, they had a tendency not to work.
The Sinclair Cambridge, and this is the later Mk 3 version, had just four functions (add, subtract, multiply and divide, plus a Constant (K) functions, which is a very crude sort of memory, but just being able to carry out calculations to 8 decimal places, on a little box that would fit in a shirt pocket was nothing short of miraculous. Sadly build quality was up (or down) to Sinclair’s usual standard and they could be quite unreliable, and the keys were such a loose fit that they rattled, but hey, this one, picked up from ebay for £20 still works, even if you do need a magnifying glass to see the display.
What Happened To It?
For a few years Sinclair did quite well with calculators and later models featured increasingly complex scientific functions but inevitably manufacturers in the Far East started churning them out at prices that home-grown manufacturers like Sinclair couldn’t compete with. In any event, by the late 70’s Sir Clive had started turning his attention to computers and within a couple of years calculators had become basic commodity items and therefore of little interest to most people. This one came with its original felt carry case and instructions, which is quiet rare. Quite a few of them were made, so they’re not too difficult to find but runners are a bit thin on the ground, and if you’re in the market for one make sure you check the battery compartment as a leaky battery will destroy the innards.
First seen: 1973
Original Price £43
Value Today? £25 0311
8-digit LED display, 4-functions plus
Dimensions: 111 x 50 x 28mm
Made in: England
Hen’s Teeth (10 rarest): 6
Mention the name Clive Sinclair and those who know of him probably think of cheap and cheerful home computers or the ill-fated C5 electric vehicle. Maybe if they are of an age, or a gadget nut like me, then miniature televisions, tiny radios, calculators and watches might also come to mind, but I doubt that very many people associate him with test instruments. As it turns out Sir Clive had relatively little to do with this side of his business but it seems that for a while it was a profitable enterprise and almost certainly funded some of his more wacky products and projects.
Throughout the seventies Sinclair Radionics produced a succession of digital instruments including multimeters and frequency meters, starting with the DM1 in 1972. This was quite revolutionary and one of the very first low cost portable digital test meters to come onto the consumer market. This model ran for three years, when it was replaced by the DM2 in 1973. Things really took off in 1977 with the PDM 35, which we’ll be looking at in a moment, as well as the PFM 200 frequency meter and in the following two years there were ever more sophisticated multimeters and even a portable oscilloscope.
The PDM 35 resembles several other products in the Sinclair range and shares the same case as the Oxford calculator, which was also used to house the PFM 200. The specification is unremarkable by current standards but back then digital multimeters were more likely to be found in a lab, than on a home experimenter’s work bench, nor were they as small or as cheap (it sold for £33.00 by mail order) as the PDM 35. It covers a useful, rather than extensive range of measurements, including AC and DC volts, DC current and resistance. The mode is selected by a pair of slide switches on the top panel and the probes plug into a row of sockets along the bottom edge. Readings are shown on a tiny three and a half digit LED display and power comes from a standard 9-volt PP3 type battery.
Operationally there’s very little to say. According to contemporary reports it worked well, though the small display was said to be hard to read at a distance or in bright light, but on the plus side it was small, light and reasonably accurate. It also proved to be fairly robust, unless you dropped it or did something stupid, like trying to measure very high voltages on the resistance or current ranges.
What Happened to it?
Unfortunately the instruments division went down the pan with the rest of Sinclair’s operations in 1979 but it was saved and re-emerged as Thandar Electronics in 1980, later to become Thurlby Thandar Instruments, which has grown into a successful international business.
Although it was advanced for its time, developments in digital test instrument design came thick and fast in the late 70s and 80s. LEDs gave way to larger and easier to read LCDs, and manufacturers in the Far East came out with cheaper and better products, leaving the PDM 35 and its successors looking a little old fashioned. For a few short years, though, this and the other Sinclair test meters sold well and they were produced in quite respectable numbers. A fair few of them seem to have survived as they regularly turn up on ebay, often in good condition and usually still in working order.
I never actually owned a PDM 35, or felt inclined to buy one as I always preferred analogue multimeters but that didn’t put me off seeking one for my collection. This example came from ebay and cost £25.00. That’s about right for one in such good condition and as an added bonus it came with its original box, leads and even a set of instructions. Apart from a loose connection on the battery clip it has performed faultlessly. Test instruments like these are unlikely to ever become mainstream collectibles or worth very much but it would be shame if they drifted into obscurity as they definitely deserve a place in the history of digital technology.
GIZMO GUIDE (manual)
First seen: 1977
Original Price £33.00
Value Today? £20
Features: 3.5 digit resolution, 10M ohm input impedance DC Volts 1mV to 1000V, AC volts 1V to 500V, DC Current 1nA to 200mA, resistance 1 ohm to 20M ohm,
Power req. 1 x 9v PP3
Dimensions: 155 x 74 x 33mm
Made in: England
Hen's Teeth (10 rarest): 4
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