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

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Old 13th Jun 2021, 11:29 pm   #1
Henenen
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Default Sony TV with distorted picture

What would cause the picture in a Trinitron to squeeze up, leaving an inch of black at the bottom of the screen?
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Old 14th Jun 2021, 8:16 am   #2
Nickthedentist
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Default Re: Sony TV with distorted picture

Known as "frame cramp" I think.

One cause can be dried-up electrolytic capacitors in the frame output stage and/or the power supply, so check the supply voltage to the frame output stage.

Note that "Trinitron" can refer to thousands of models from the late 1960s to the early C21st, so a model number would be handy
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Old 14th Jun 2021, 8:41 am   #3
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Default Re: Sony TV with distorted picture

As stated, dried up caps and depending on the model, dry joints on frame o/put IC.
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Old 14th Jun 2021, 11:01 am   #4
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Default Re: Sony TV with distorted picture

The capacitor responsible is usually right by the frame chip. Large-ish electrolytic. There are only a couple - change both and see to the dry joints and the set will be fine again.
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Old 14th Jun 2021, 11:18 am   #5
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Default Re: Sony TV with distorted picture

Seem to recall the value was a bit of an oddball one (these days anyway) in many Sony's. Was it 680uF. You could fit a 1000uF but it wasn't quite right linearity wise as I recall.
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Old 14th Jun 2021, 12:06 pm   #6
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Default Re: Sony TV with distorted picture

Boot strap capacitors , used it increase voltage on frame output ic to speed up
fly back time so that next field could start at the right time. There is a diode from the line output transformer that might be o/c and in some sets a resistor
that might be high or o/c.
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Old 14th Jun 2021, 1:01 pm   #7
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Default Re: Sony TV with distorted picture

Exactly - usually it's just the capacitor that fails. Usually the compression is noticed before the chip and feed components fail unless you had a very uncritical customer who ended up paying twice as much for the repair!
ISTR 680 or maybe 820uF?
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Old 14th Jun 2021, 1:32 pm   #8
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Default Re: Sony TV with distorted picture

820uF, could well be Glyn. It must be over 20 years since I last did one.
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Old 14th Jun 2021, 1:54 pm   #9
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Default Re: Sony TV with distorted picture

Awesome, thanks guys.
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