Fernseher und Farbfernseher aus der Anfangzeit des Fernsehens und des Farbfernsehens - Homepage Eckhard Etzold
One of the most famous and unusual tv sets was made in U.K. by Bush. It is the
TV22. In comparison to today's tv sets this set operates with the historic
british television norm of 405 lines per frame and positive video amplidute modulation. The audio signal
was also broadcast in amplidute modulation and not in FM like in the U.S. and continental European postwar
tv standards. The BBC one programme in British 405 line standard was broadcasted until 1985 before it was switched off.
Since 1985 all British tv programmes were broadcasted in 625 PAL television standard.
The case of the set is made of bakelite, the design was dominated by round curves and the round screen of the 9 inch picture tube. This set became a worldwide famous example of British industrial art and design. In 1950, this set was sold for £36 and £42. More informations are available on the web: 1, 2.
Since my childhood I was familiar with German tv sets and their schematics, and since the last years with the upcoming of
the internet with American television technology. But when I got this Bush TV22 in May, 2006, I took a short view on it and put it away.
This set looks completely different to what I have seen before. The schematics are very strange. I was wondering about these few parts in it
in comparison to our German tv technology. Later I learned from Darius, an friend of mine here in Germany who is familiar with this tv standard,
that this strange look depends on the British television standard. With this positive video modulation there are not so many circuits necessary
to generate a proper picture on the screen.
In January 2007, after a long time of talkings and research about the specials of the British standard, I felt confidence enough for restoring the
set. The picture tube was tested. There was no emission. Absolutely zero! I gave power to the filaments and heated the picture tube for 24 hours.
But again there was no emission. This valve was dead.
The chassis looks really bad, the tar insulation of the line output transformer was dried and cracky. Darius said, this is not problematic. It will work fine when the set is in operating mode.
I have checked the schematics and found that the most critical wax capacitors are on the main deck. They are the coupling capacitors and the line and frame time base capacitors. Only these capacitors were replaced: on the main deck and the side plate C24, C26, C27, C29, C30, C31 (both for proper brightness), C52, C56, C57, C58, C59, C60, C61, C62, C63. So, in my opinion, in the TV22, 15 capacitors are at least really critical. C74 is critical of course. But if C74 has leakage current, the fuse will melt. So you can decide to keep C74 until the fuse acts. After that the set was switched on again. A blue glow inside the PL 38 seems to be suspect. I asked in Paul Stenning's forum for that, but I got the answer: PL 38s can glow blue like that with no problem. I got a very dim raster. Darius borrowed me a self-made analogue standard converter for the London Alexandra palace transmitter (Channel 1). I got no signal. This set was made for the Birningham area and not for London. But with some fine tuning it was later possible to display a signal. As one can see there was no synchronisation. The line frequency was below tv standard. I could not step up it. The value of a resistor which was in series with the horizontal hold was increased. I soldered a 100K resistor parallel to it. Now I got the correct line hold frequency. But still there was no synchronisation.
While measuring the grid and anode voltages at the pentode of the ECL 80, I found that the anode voltage at pin 6 was only 2 V. It should be appr. 140 V. This misfunctioning depended on a leaky capacitor C55 which was soldered below the main deck plate, so I forgot to replace it. After that I got a first picture with full synchronisation. Features like AGC or vertical and horizontal blanking were omitted in the Bush TV22. But as far as I can see, they are not necessary here.
While testing the set, suddenly there was a failure. From one moment to another I got a very quiet line whistle, a short moment only a vertical line and then no high voltage, no picture. At first I thought the line output transformer was burned. Of course it looked very bad. It looks like some tar melted. For safety reasons I inserted a resistor between screen grid of the PL38 and booster voltage like Darius has recommended it.
Darius gave an instruction how to measure the resonance frequency of the line output transformer to find out whether it is dead or not. He found 38 KHz with 1 Vpp on his line output transformer. I found 110 KHz with 0.3 Vpp and 230 KHz also with 0.3 Vpp. In the expected range around 38 KHz there was nothing. This was suspect. Darius' next hint was to test C34 (see schematics of Paul Stenning). This is the small flat mica capacitor at the line output transformer (T2 over d and e).
There was a short in C34 , the 470 pF capacitor parallel to the line output coil which I had replaced before with a 630 voltage d.c. type.
All I can say is that in Scotland, unlike England, very few people could afford these sets when they were being sold. Most Scottish people, especially children, would have a friend in the area whose parents were wealthy enough to own a T.V. and on certain days when something special was on TV all the local children would gather in the friend with the TVs house to watch that programme. Adults would be invited by friends with TV to see special programmes, inc. football, tennis etc., etc.He wrote about the Birningham transmitter:
I cannot say for certain, but can say that the Independant Television Co., which introduced advertising and started transmitting in the 1950s had a Transmitter in an are midway between Glasgow and Edinburgh, Scotlands 2 main cities. The programmes did not run for long during the day, most often starting at lunchtime 12.30.am, with a lunchtime easy listening,easy viewing programme. This ended at 2.00pm and transmisson started again at 4.30/5.00pm, continuing until approx.11.30 / 12.00am at night. The programme transmission always ended with a short( 5 minutes) Christian religious message from a minister or priest and "God save the Queen" anthem. A Christian message would not be tolerared nowadays in this mad Politically Correct(p.c.) world but it has to be said that many old people enjoyed a few minutes of religious texts or stories before going to bed.
Please ask Paul Stenning.
6 x EF91, 2 x EB91, 2 x ECL80, PL33, PL83, PL38, PZ30, EY51, MW22-16
Photos: © Eckhard Etzold, 2006, 2007.
Technical Info and Restoration Tips On TelevisionsZur Homepage
BUSH TV22 Mk.1
BUSH TV22 Television
TV22 Restoration - A great thread in Paul Stenning's forum
Fernseher und Farbfernseher aus der Anfangzeit des Fernsehens und des Farbfernsehens
Homepage Eckhard Etzold