|Electronics & DIY
|Circuits & technical
|System 2000/3000 amps
Once again I was commuting fairly often to Thetford, to get the new Stereo 25 and PZ3 into production at Harvey Hall Electronics Ltd. in Thetford. The rest of the time I was helping the Comberton branch move to the new premises. Or doing a few repairs.
The official move was in April. I was at 22 Newmarket Road waiting for Jim Westwood and Martin Wilcox when two new people turned up: Lindsey Lloyd and his follower - a rather nervous Christopher Curry! And then there were five! We were in two rooms on the top (second) floor of the premises.
I had a Leak Stereo 30 amplifier driving a pair of large bass-reflex loudspeakers which were high up near the ceiling. I was into classical music and these parties always did well on music such as Offenbach's can-can, Rossini's William Tell overture, Radetzky March and similar popular clasics. Chris Curry has thanked me for the training I gave him into classical music! Chris says "Berlioz' March Hongroise (from The Damnation of Faust) was what compelled Jon Harris to have you (and me) turfed out of that wonderfully convenient flat opposite the Turk's Head in Green St - incidentally Jon Harris lives there to this day!"
It was during this period that Jim Westwood got disillusioned with Clive Sinclair and left Sinclair Radionics. He got a job as a gas-fitter, doing natural gas conversions for Gascol. But it took less than a year for him to get disillusioned with his disillusionment and return once more to Sinclair Radionics, where he stayed close to Clive Sinclair for the rest of his working life.
Martin had just bought a new wrist-watch. He was inordinately proud of it and kept checking the time against the mains driven wall clock. To the extent that Chris and I got fed up with it! In those days such a clock would keep time by using the 50Hz mains frequency. So, when Martin went out of the room, I got out a signal generator, connected it to an amplifier and power supply and used it do drive a mains transformer in reverse so we could feed the clock with the high voltage from the transformer. While I was doing that, Chris told the folks in the next door lab what was going on. Then Martin returned, we increased the signal generator's frequency so the clock started to run fast. Martin got worried and asked us the time - but Chris and I gad been advancing our wrist-watches to agree with the speeded up wall clock.
So Martin got up and went next door. But we had used the intercom to tell them the time, so their time agreed with our wall clock. Chris Curry recalls the incident: "you had rigged the wall clock to a signal genny and we all watched while an hour passed in about eight minutes. Martin characteristically failed to see the reality and after getting more and more irritated about his new watch stomped off home muttering only to bump into Clive on the stairs - such was Martin's mood that he ignored Clive's curiosity and left anyway and we all had to keep quiet about the trick!"
Then there was the time that Martin took up betting: he had this system where you start with a (very) small bet. If you win, you pocket the winnings and start again.
If you loose, you increase the next bet so that, should you win, the winnings will cover all your losses to date. When you do eventually win, you start again with the small bet. Martin came in one day very pleased with himself, he had won! I forget the exact amount, maybe 5 shillings!
But with the move to Newmarket Road, I was now handling all after sales contacts with customers, so was in-charge of servicing. I started quality sampling some of Malico's repairs: they were often not up to standard! Because of the source of the transistors, sometimes thee needed to be changed to get full performance.
I drove Jim down from London to Earls Court. Jim was holding the Micro-vision carefully as it was a very early prototype so very much of a bread-board, even it a sub-miniature one! His was naturally interested in how the TV coped with the varying signals between Cambridge and London, so he had the set switched on. It worked fine - even it re-tuning it was very fiddly. Signal strength is London was very variable at ground level and it would often fade out when shadowed by a large building. But I can say that we had the world's very first in-car television!
Naturally the Micro-vision was something of a show-stopper. But the prototype really was not suitable for production and a saleable model was still many years away. The Microvision did not become a product until 11 years later. in 1977!
The Micromatic was a cosmetic improvement on the Micro-6. The earlier Micro-6 had an adhesive gold label on its front. The Micromatic upgraded this to an adhesive-backed brushed aluminium decal. To avoid the plate damping the ferrite aerial excessively the lower half was pierced with decorative holes.
The adverts for the Micromatic were phrased in Sinclair's usual enthusiastic manner, with such phrases as "Plays anywhere", "Amazing performance", "Bandspread at high frequencies"
So one customer returned his Micromatic with a comment "If this is amazing performance, then, truly, I am amazed!."
The "Bandspread at high frequencies" was quite correct: the tuning device was a compression trimmer, where two plates were separated by a mica sheet, The top plate was a springy one so that when the device was unscrewed by the tuning dial, the plates sprung apart reducing the capacitance. The change in capacitance was greatest when the plates were close which gave low frequencies. The change got less as the plates opened, giving a non-linear tuning range, so "Bandspread at high frequencies"! However, because of component variation, it was sometimes very difficult to get the tuning scale to coincide with actual performance! Especially if the dial had been removed for servicing. This almost invariably meant fitting a new dial plate,
The Micromatic was a very successful product! It started life in early 1967, and was sold until the middle of 1971. There are various pictures of it in the images directory.
A loudspeaker may sound impressive at first hearing, with impressive bass or crist treble, but many of these can, Wes found, be tiring for sustained listening.
The Q14 was released in the autumn of 1967. In 1968 it, with other hi-fi products caused much excitement at the London Audio Fair at Russell Hotel, but that's another story for later.
There is a review of the Q14 in Tape-Recorder magazine, June 1968. Denys Killick said "The sceptics will have already raised their eyebrows. They will be thinking - as I did - that all this sounds much too good to be true. I will excuse anyone who glances at the price, shrugs his shoulders and dismisses the Q-14 as being unworthy of serious consideration. But this would be a most serious error of judgment. After a great deal of listening I have formed the positive and unshakable opinion that in the Q-14 we have the very finest value for money that it is possible for anyone to buy today."
There was one problem with the Q14: the magnet that was in the drive unit was bonded in place with a glue which, frankly, was inadequate. If the speaker (or the parcel containing it) was dropped in the wrong way the magnet would slip and the whole speaker was then useless. Of course Sinclair, true to their advertised conditions, replaced these without quibble but we ended up with quite a pile of dud Q14s!
Chris Curry was kept quite busy installing hi-fi systems for customers: as he says I installed Z12/Q14 systems all over Cambridge and helped the odious Alan Sugar make his first Stereo 60 based hi-fi and the wonderful Wes Ruggles to make his portable sound system, designed a unipivot arm and experimented with direct drive turntables....
The Neoteric saw the light of day early in 1968 just two years after we had moved to Newmarket Road. The Neoteric was first demonstrated at the 1968 London Audio Fair at Russell Hotel. Unfortunately the original design was something of a disaster! Martin had decided that he would make the inside modular, so there were two power modules and a preamp. But the mechanics of this resulted in various metal sub-chassis and the whole thing was difficult to build and near impossible to re-work - in those days all such things were hand-assembled so production errors were not uncommon and faults had to be re-worked due to "finger trouble" as Harvey Hall (who was building them) called such mistakes.
As a result very few of the early units were made and a new engineer, by name of Keith Pauley, was put to the task of re-laying the circuit to make it producible. Keith did a very good job and the Neoteric Mark 2 was a firm success: today, nearly 50 years later it is a much sought-after unit. I have one myself! There are probably no Mark 1 Neoterics around today - if you know different, please contact me!
However there are a number of adverse criticisms of the Neoteric on the www. These all appear to refer to the early version. The Mark 2 seems to have cured all.
The System 2000 amplifier and speakers were first demonstrated alongside the Neoteric at the 1968 London Audio Fair at Hotel Russell, April 14th to 17th. There is a gallery of photos of the System 2000.
The early amplifier (which I worked on) used all germanium transistors and the circuit was not dissimilar to that used for the Sinclair Z12 and Stereo 25, with a few improvements. The power transistors were wired to the PCB with coiled resistance wire in their emitters to make am emitter resistor. However the early 2000 amplifier was implemented at a time when silicon transistors were gaining popularity and germanium was on its way out. The supply of transistors which Sinclair had obtained from Associated Transistors was running out. So the amplifier was soon redesigned as detailed in the circuit and board information on the System 2000.
The first silicon transistors we used were manufactured by Microelectronics of Hong Kong. The silicon chip was positioned on a ceramic base and capped with an epoxy dome (they can be seen in the photo). But in the early days the epoxy capping was not always good. The epoxy needed to be applied with enough pressure to orce it down the lead holes in the cerami base to ond the gold-plated leads firmly. If pressure was inadequate the legs of the transistor (which passed though the ceramic base) would not be sealed so could rotate, breaking the internal bond wires. Also, it the epoxy did not properly bond to the ceramic, pressure on the transistor which pushed a lead up into the body could cause the transistor to raise its cap. This would happen if, for example, the transistor received a sideways knock when soldered into the board. This was a common problem.
As I recall, that period did not last long. We started looking for new premises for the service department. Then AIM - a spin off from Cambridge Consultants Ltd. - vacated their premises at 71-73 Fitzroy Street, moving to Enderby's Mill in St Ives. Clive Sinclair had always been close to Cambridge Consultants, so the service department moved to AIM's old premises. Aim left Fitzroy Street at the end of 1968 so the service department's move must have been early in 1969.
I then had room to start employing staff: mostly female who I trained up to service the various items. Mostly returns were for similar reasons, and once the reason had been identified, it did not need highly technical staff to repair the item: servicing was something of a production line. Also, to be honest, O found the ladies to be more reliable. In those days most women had little self-confidence so needed a lot of encouragement but once they had realised they could do the job, they got a lot of satisfaction out of it so were very reliable. Sales were increasing so fast that even when a manufacturing fault had been located and fed back to production, there were hundreds - even thousands - of items which might have the same problem.
The Z12 and System 2000 were going strong. Both used germanium power transistors. Clive had negotiated with a new supplier to buy all their surplus stock. He had given them an absolute minimum test specification; something to the effect that, with 100mA base current, the collector current should be not less than 1 amp.
That test specification did not then reject very leaky transistors with an even lower gain. Suddenly we were inundated with problems. I located the cause of these and built a transistor tested which would pulse the transistor with a ramped up base current. The voltage driving the current through a suitable base resistor was then used as the X-axis of an oscilloscope display while the collector voltage was used as the Y-axis. Thus a graph could be drawn on the 'scope which would show voltage breakdown, leakage and gain. Once this test was implemented and the tested transistors were used for production, problems ceased.
The tester was based on the improved emitter-coupled multivibrator which I later published on www.4qdtec.com.
The test was therefore quite simple. Because the high current was pulsed, the transistor being tested did not heat appreciably so could be handled easily. Sometimes a transistor would indeed start to heat very quickly: a short-circuit dud! Testing was done by the daughter of one of the women doing repairs, who came in after school. But we were rejecting huge quantities of transistors. Yield was at one time very low - so the specified minimal test was altered. But Germanium power transistors were now going out of fashion. Silicon had started to dominate.
It was in late 1968 that Sinclair announced the IC10, an integrated amplifier made by Plessey and re-badged by Sinclair. But there were production problems. Sinclair had arranged the usual massive advertising to announce a new product - advertising had to be booked several months in advance! But Plessey could not deliver. There were production problems. In February 1969 a whole page of Sinclair's advertising was given over to an apology for the non-availability of the IC-10.
Fitzroy Street did not last long at all: the service department outgrew it within two years. AIM had moved to Enderby's Mill, but the premises there were huge. The whole of Sinclair Radionics moved to Enderby's Mill in April 1971. But I moved the service department to the mill 6 months earlier: in October 1970. But I get ahead of the products!
In November 1969 the new Z-30 was released with a new preamplifier, the Stereo-60, and a choice of two new power supplies: PZ5 (unstabilised) and PZ6 - a higher power stabilised power supply. To-date, I had written instructions for all the hi-fi range (with the exception of the Neoteric). I also wrote the Project 60 instructions, with drawings done by an excellent free-lance technical illustrator by name of Stan North. The manual is extremely comprehensive! Being the person who had answered all technical enquiries and done servicing on the Z12, I knew what people had tried to use them for and I covered it all in the Project 60 Instruction manual.
The whole 17 page A4 size manual for the Project 60 is available, with other technical information which is slowly being added. The manual includes circuit diagrams and component layouts for the Stereo 60, Z30, PZ5 and PZ6, with many application notes.
At least, that was the theory. In practise the leads were not always properly held in the ceramic and the act of spreading them to fit the board would sometimes break them loose. And a slight sideways pressure on a transistor would sometimes be enough to break the ceramic-epoxy bond: a lead would then push upwards and the top of the transistor would pop off. This of course caused problems in production and breakages in transit, and in the customer's hands!
The other problem was with the power transistors. The chip would get hot and the silicon, lead wires, ceramic and epoxy would all expand slightly. The very slight different thermal expansions would cause failure of the bonding to the chip.
These problems caused Sinclair to stop using these transistors which meant a re-design of the Z30. In place of the ME transistors Sinclair made a contract with Texas Instruments to have newly fabricated transistors tested to Sinclair's own specification. I still have these specification sheets and may publish them - so please ask. These are not reject transistors - they would pass as normal branded transistors - but the selections are such that they would work properly in the circuits as designed. The redesigned amplifier was released in 1970 but the redesign allowed two versions: the Z-30 and the Z-50.
The pots were linear, so volume matching was sometimes not good at the bottom end. And the aluminium could twist slightly so balance was not always perfect. But considering that the Project 60 enabled a user to afford a hi-fi system for a fraction of the price of other systems, these were good compromises.
So we had to simply accept such failures as did occur. But, where repairs were not covered under guarantee, there was a low price fixed charge for service. A kit project such as this was aimed at a dangerous market and high returns were always likely: the adverts did say anyone could do it. Many of out customers were not "anyone"! In electronics (and most other fields!), there have been many idiot-proof designs which have not been customer-proof!
The Project 60 continued to be a good seller and further units and upgraded designs were released for it until it was superseded, after 4 years, by the Project 80 in late 1973, But more about all that in the next part.
One problem emerged - in the vicinity of a radio transmitter, the amplifier could become a radio receivers and the local radio station would be heard weakly in the background. Production was modified by fitting two extra capacitors and if any customer complained of this problem we would send them two capacitors with a technical information sheet showing where the capacitors should be fitted - and a letter saying that if they preferred to return the amplifier to the factory we would of course fit the capacitors at no charge.