Sony Trinitron KV-M2120U wobbly vertical deflection

[Maarten]

I'd start with checking (scope needed) all signals around the horizontal sync and output stage. It looks a bit as if not only the vertical deflection is affected.

[Retrorepair]

I agree, I need another scope I think.

[Maarten]

Come to think of it... Could it be one of the harmonic tuning capacitors in the horizontal output stage? I don't have the schematic handy, but if the sandcastle signal is derived somewhere around there, it could cause strange deflection problems.

[IKC2E51R8]

have you tried changing the Vertical size control potentiometer, ive had similar faults caused by a bad potentiometer.

[Retrorepair]

Originally Posted by Maarten

Come to think of it... Could it be one of the harmonic tuning capacitors in the horizontal output stage? I don't have the schematic handy, but if the sandcastle signal is derived somewhere around there, it could cause strange deflection problems.

That's worth looking at, thanks!

[Retrorepair]

Originally Posted by IKC2E51R8

have you tried changing the Vertical size control potentiometer, ive had similar faults caused by a bad potentiometer.

I haven't, to be honest it seemed like there was no sync at all but by this point worth a shot.

If it helps diagnose, the image got like this over maybe a minute. Started off a bit jumpy then just slowly shrunk and went like this. Still jumpy. Sorry I realise that's a crap description.

[Maarten]

Originally Posted by Retrorepair

That's worth looking at, thanks!

Or possibly any part in the vicinity that may be internally arcing or open crcuit.