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Sony KV29X1U (BE3D Chassis)

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Turnip:
Hi folks,

Chap struggled in with a mere 29 inch, and said 'Sound OK, and if you wait an hour or two you get a picture')

Shorted a RGB output collector to deck and noticed Field collapse. Remembered dry joints on the STV9379 FOP were the main problem, so first re-soldered then replaced it - Still no field.

Checked supply voltages - + and - 15v OK. Wonder if there's another common cause, as perusing the manual, the FOP output seems to go directly to the scan coils without a coupling cap.

Never had O/C field scan coils since the 60s, when Philips had them all the time, as think they incorporated a thermistor that went O/C, and as the coils were potted, no repair was possible.

Thanks for any thoughts - Chris.

jordan:
Picture tube defect...up G2

downunder:

Hi Chris, the auto grey-scale trackingis no longer able to function, probably due to the CRT ageing. Suggest shorting out R728 on the CRT base.

Should give it a bit more life.                   Bruce

Turnip:
Thanks Jordan and Bruce,

Had another look with a RGB collector flashed down to deck and noticed not just no field but very little width either.

Overnight had a feeling that the Pin correction to the middle of that dual diode on LOP collector might be suspect so shorted the bottom diode to deck - Surprisingly no difference to the width but the field popped up to normal and stayed there.

Gave up at that point but suspect an O/C cap somewhere in the LOP area as EHT is also low, but supply is normal at 135v so don't suspect supply reservoir cap duff.

Thanks again, wouldn't normally bother with tube sets but things currently quiet - Chris

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