Brand : Sony 21”
Model: KV-M2151A ch. BE2A
Schematic : eservice dot com
Fault : intermittent narrowing and widening picture
The fault crops up when the chassis is moved even slightly so I think it may be a false contact.
This Tv has an East-West correction section even if it is a 21″, so I turned my attention to this part of the chassis. On my first inspection with the magnifying lens, I did not see any dry joints. This time it doesn’t seem to be the usual capacitor soldering problem that was connected to the coils and integrated circuit.
I noticed “strange movements” on IC801 output waveform when tested with the oscilloscope; the input the sawtooth wave was normal and constant. I replaced on a trial basis the integrated IC801 (BA4558) and also Q803 (2SD1761), but no change (it was a normal transistor and an operational IC so I did not have to order the spare part).
At this point it boils down to checking resistors R806 and R808 (respectively 1Kohm and 56Kohm), two SMD resistors which form a reaction circuit, on soldering these two components I have resolved the problem. When I moved the chassis (without exaggerating obviously), there were no more intermittent narrowing and widening of picture problem.