Monday, March 24, 2008

BC108 Analogue Gem

The BC108 transistor along with it's companion BC107 and BC109 became the heart and soul of project building! This general purpose silicon device (which sort of replaced the old OC71 germanium device) could be used for audio pre-amps, drivers, oscillators, multivibrators and even switches. I even used them to replace odd sounding NPN transistors in televisions, audio units and video recorders. Faulty japanese and foreign transistors that were impossible to find or expensive to order could usually be replaced by this lovely 10 pence little gem!

Later, the black plastic BC148 came along which was the printed circuit version and the BC158 which was the PNP version.
You can still buy the BC108 at Maplin and Modern Radio...
An analogue gem!

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.... "

Friday, March 14, 2008

The AVO 8 - analogue battleship!

I've got to agree with this, the AVO 8 was a suberb instrument. The one I used to own was the next model up, just different knobs. When I left Servicescope I should have kept hold of the AVO as it was mine! It fit nicely into a Mothercare box and went everywhere with me!

"In my opinion you are now looking at one of the finest electrical test and measuring instruments ever built and until a few years ago, if you ever needed to have a piece of electronic equipment repaired there’s a very fair chance an AVO meter, and quite probably a Model 8, had something to do with it.

By current standards the AVO 8 is fairly basic; all it does is measure AC and DC voltage and current and electrical resistance. You can buy a pocket test meter in Maplin for under a tenner that does all that, and quite a bit more besides, and probably more accurately -- but I absolutely guarantee it will not be still working in 40 or 50 years time. AVOs even older than that are still in daily use. What an AVO 8 and analogue meters lack in fancy features they more than make up for with the extra information they provide about the circuits they are being used to test. It takes a while to learn and understand the behaviour or a wiggling moving coil meter but it’ll tell you more than a bunch of digits ever will. However, what really sets the AVO 8 apart from almost every other test meter is its rugged construction. In short it’s built like a brick outhouse and can take a ridiculous amount of physical punishment, and if you do abuse it electrically the fast mechanical cut-out usually saves the day."

They don't make 'em ilke that anymore!!

Wednesday, March 12, 2008

Walkie - Talkie!

Speaking of Pirates......

Back in 1968 my friend Paul aquired a 27mhz walkie - talkie like the one above. In those days these were illigal and could not be bought in shops. I seem to remember that he won a set of these at Bingo at Pontins! These things were pretty nasty...range of about 100 yards and a super-regen receiver that created a huge amount of noise. Paul lived about 200 yards down the street from me and with the walkie-talkie's own telescopic aerial it just didn't reach bedroom to bedroom. So I decided that if I connected my own outside longwire aerial to the walkie- talkie we should be able to increase the range. It did! I could sit in my bedroom and talk to Paul in his own bedroom - brilliant!!
So one afternoon my Dad came into my bedroom to see what I was up to, I was talking to Paul on the walkie-talkie. As a joke, my Dad took the walkie - talkie and said "Hello...Victor...Victor...netting started..."
Paul was shocked...he thought the Police were on to use!
My Dad carried on with this for a while until Paul came running up the street heading for our house. We played on a bit longer before telling him it was my Dad winding him up!
We used these walkie-talkies for a while until one night I had a knock on the door from a woman who lived at the back of us. Their Television was completely blanked out. When I went round to investigate, I discovered that it was the RECEIVER that caused the problem not the transmitter. It seems that when the receiver was running every television in the neighbourhood was wiped out. Details of the walkie-talkie are here:
Needless to say I soon closed down and hid the beasts!!
Nowadays walkie-talkies and other 27 Mhz equipment is legal and can be bought anywhere. I now have several remote-controlled airplanes digitally controlled. Great!
This website is fantastic some super retro stuff here that brings back memories!

Saturday, March 08, 2008

Pirates of the Topband

The famous WS19 set as used by all good pirates!

Thinking about reel to reel tape recorders brought back some memories of the golden days of pirates. The Topband Pirates of Bolton!

Many an evening and Sunday afternoon they could be heard, signals as rough as a bears arse and as wide as a barn door that completely blocked out the 160m band. Cheeee Coooo, Cheee Cooo from G3Y Cheee Kaay!!! There were usually four or five of these guys, mostly in the Breightmet area.

Back in 1970, one Sunday afternoon, I went to my friend Neil's house in Astley Bridge. Neil had just completed building a topband transmitter and waiting for his licence to come through. He also had a tape recorder, a Marconiphone if I remember right. He had connected this reel to reel beasty to his Topband Transmitter and Receiver. That afternoon was probably the most hilarious afternoon on the radio ever! As the pirates called to each other we recorded their messages and then played them back on Neil's transmitter which totally confused these IQ1 pirates. We led them astray for the best part of two hours before they realised that someone was taking the p**s! The best bit was when one guy jumped in, in a state of panic, and shouted "It wernt me, I were peeling spuds at the time!"

A wonderful time was had!

The Pirates of Topband stayed around for a while until the local GPO guy, Gerry Openshaw decided to pay them a visit. Before this however, we decided to pay a visit to 'Vic' who signed himself G3YCK. We knocked on his door one Sunday afternoon and was invited in to see his equipment. There, in the corner of his front room was this enormous ex government transmitter, no furniture, or carpet...just this analogue monster and a load of kids running amok around the house!

Those were the days!

In the digital world, Hackers, Advertisers, Spammers and the Virus Pirates are the ones to watch....and you can't just knock on their front door!

Friday, March 07, 2008

Reel to Reel!

This is not the exact reel to reel tape recorder that i'm talking about, but fairly close.
Back in 1967 my Dad came home with a TAPE RECORDER that he bought from my Uncle Bill. With it came a tape of Herp Alpert and Frankie Lane.
Reel to Reel Tape recorders were an absolute luxury then!
It was an Ekco reel to reel tape recorder similar to the one above with the same BSR tape deck. The button on the left you pushed up when recording and pushed the right button up at the same time. At the bottom was a 'Magic Eye' to display the recording level.
What an amazing piece of technology! Every Sunday I would record the top twenty, at first using the microphone, but later by using a lead to connect directly to the radio speaker with crocodile clips which meant you could talk while recording.
I used to listen to the top twenty every night in the kitchen and carried this heavy beast down to my friends house to listen when his Mum and Dad went out.
Later, I used the reel to reel to learn morse code with George's tapes and listen to Blaster Bates recordings that came with them!
It certainly got a lot of use by me!