Friday, March 21, 2008

Analogue Daleks!

Not what it seems...this famous Amstrad HI-FI system looked good in the corner of a living room, but was probably the worst audio system in the world! Not seperate units, but four big screws that lowered the whole front panel built into the wooden case. Record Deck a waste of space and speakers rubbish. These objects were like Daleks and would often take over the workshop as they were so unreliable! In the words of Alan Sugar (Managing Director of Amstrad) "Your Fired!!"

I stumbled onto this while searching for a picture of the old Thorn 3000 chassis! I could have changed some of the words to make it sound like my own experiences and believe is all true!
By Jim Ollerhead

"I vividly remember getting a 'belt' from a CRT final anode, especially the Thorn 3000 series colour TV. This was a panel-swap model, the guys in the field just changed the circuit boards and we fixed the panels back in the workshop; we used to sneeringly call the field engineers ‘panel pushers’. Anyway when you got a shock from this TV you involuntarily snatched your hand out from the box-shaped chassis and all the soldered joints under the panels left a fine lattice of scratch-marks on the back of your hand, eeeeek! Happy days, not!

Working inside the back of a colour TV can be a hazardous business, especially to the backs of the hands...

When I first joined Rumbelows black and white 405-line TVs were still around but they were being phased out as I started my early career as a telly engineer. This was at the beginning of colour broadcasting in the UK and Beeb 2 used to show those peculiar European test transmissions, or just a test card.

The first sets I worked on were Baird valve jobs in huge spine-breaking cabinets. As an apprentice I used to go out with the "collect and loan" bloke. At the time there were also loads of black and white dual-standard (405/625-line) sets around with a 12-inch long system switch across the back of the circuit board. This was often the main cause of problems and was usually fixed by some judicious squirting of Genklene whilst vigorously waggling the switch side to side. It was then topped off by a final spray of Amberlube, which didn't evaporate like Genklene

There were lots of Baird mono TVs around back then, but my favourite was the Thorn 1500 model because it was such a doddle to fix. It always brings to mind the Led Zeppelin track Black Dog (on LZ4) that has a line in it that says "I don't know but I been told a big legged woman ain't got no soul". Amongst my fellow engineers this became: "I don't know what I been told but C98 got no frame hold’. C98 was the bypass capacitor for the PCL805 frame oscillator valve and it used to fail regularly and cause a rolling picture in the 1500.

Don't even get me started about setting the static convergence on a Thorn 3000 TV, trying not to let your hand tremble as it twisted the circular magnets on the (bloody high voltage) scan coils, whilst trying to hold a mirror and looking at the cross on that 'orrible kid's chalkboard on Testcard F. it's amazing any of us survived!

70s TVs like this one relied on replaceable circuit boards or 'panels' that were swapped by a visiting engineer and then taken back to the workshop for repair

We used to carry with us workshop-cobbled "tube-bashers". I think the circuit came out of the now-defunct Practical Wireless or Television magazines and consisted of a few components but it had a quite impressive 60W light bulb on the top that flashed as the basher did its work. Basically it hammered the cathode of the tube to try and burn off accumulated deposits to eke a few more months’ life from the picture tube after the images had begun to take on a 'silvery' appearance.

I well remember power supplies in Thorn 3000 series TVs, These had large ‘dropper’ resistors and after a while they began to look like a bunch of grapes. They failed frequently so engineers just ‘bridged’ the faulty one by soldering on new droppers.

Latterly I became the "audio bloke" and this coincided with the influx of cheap and crappy music centres, which took over from coffin-shaped radiograms. There was one long standing problem with a Waltham music centre. It kept coming into the shop with blown output transistors and I couldn't understand why. It was fixed checked and sent out in fully working order but the next day it always came back.

The ubiquitious 1990's 'music centre, this one is a cheap and cheerful fake Hi-Fi stack system and the bane of service engineers

It finally dawned on me that when you screwed down the transit screws on the record deck -- two big fat screws that stopped the deck falling off its coiled spring legs when it was being moved -- the deck touched the heat sink tag of the output transistors. If the transit screws were not undone as soon as power was applied the transistors blew.

Another music centre I’ll never forget was the Thorn Pilot, I even bought one. I thought it looked really compact and neat with it’s rounded contours. The problem with this one was the tuner cord -- basically a string that connected to the tuner knob to a pointer that moved along a tuning scale. The cord path was a bit of a nightmare (as were many others) because if you had never seen it threaded up and it snapped, trying to guess the route the cord took around the pulleys and tuner spindle was a near-impossible task. Of all the things I hated most about being Mr Audio, restringing tuners was the worst.

It wasn’t only music centres that caused me grief. Some customers seemed to think that if the tape reels in a Compact Cassettes stopped turning a liberal dose of 3-in-1 oil would free it up. In fact the mechanism was quite complex and relied on friction to work properly. I got so pissed-off with people's DIY efforts to fix cassettes that I wrote a two-page article, which was published in Amstrad Action magazine.

During the early 1980s the pace of technology was accelerating and a friend at Rumbelows lent me a Sinclair ZX80 computer. I recall being thoroughly amazed at this tiny machine's ability to allow you to type instructions into it and to actually follow them. This was the dawn of my desire to find work as a programmer. I have worked in IT for some 22 years now but it's all too easy to forget those early days.... "

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