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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc.

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Old 15th Sep 2021, 10:18 am   #21
xereeto
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Join Date: Sep 2021
Location: Falkirk, Stirlingshire, Scotland
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Default Re: First repair project - PYE 450 (Philips G11). Weird beam distortion.

OK I think I may have been a little dramatic - a friend suggested dry joints could be the problem again as I may not have properly fixed them, so I reflowed every joint on the neck board and power board again. Hooray - the tube lit up and displayed a picture.

However the image has ripples like the surface of water, and I'm 99% sure that - just as before - if I left it on for long enough it would develop the pincushion distortion again. So I guess back to the drawing board.

I haven't seen anyone mention it, but am I right to suspect capacitors for this? The problem builds gradually over time that the TV is switched on, and once the fault has set in it persists until the set has been off for some time. I had this exact behaviour (though a different fault) with a laptop's gas plasma display panel once, and fixed it by recapping the entire driver board. Just a thought
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Old 16th Sep 2021, 8:23 am   #22
Welsh Anorak
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Default Re: First repair project - PYE 450 (Philips G11). Weird beam distortion.

In a word, unlikely.
Capacitors are seen, justifiably in many cases, as the bÍte noir of modern electronics, partially because they need to work much harder with switch-mode power supplies. However old-school electronics like the G11 used good old Philips capacitors in proven circuits that are very reliable. The trouble with the red electrolytic was a manufacturing problem.
Of course at this age it is possible some capacitors have deteriorated and it might be a good idea to re-check the blue main smoother just in case. However I still would direct you to the active smoothing circuit. As a rule, pincushion distortion is a fairly static phenomenon with both sides pulling in. Your picture has the hallmarks of smoothing problems.
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