Electronics > Repair

PVM monitor repair

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fabiodl:
I have a sony PVM-204M
Its service manual is here

All of a sudden, I got the RED, GREEN & BLUE lines displaying on the top of the screen as shown


I fully recapped it (155caps!) but the problem remains. Indeed, the ESR of every single cap was ok.

I am worried connecting a faulty console to it may have damaged it.
Video signals are still shown correctly, so let's say a faulty power brick let 110V through the console and through the video inputs. Wouldn't that have damaged the whole input section? However it's only the vertical position which shifted all of a sudden.

What would be your next action?

perieanuo:
the menu shows up ok? if it shows, then yes you have popcorned your input stage

perieanuo:
on page 42 i see some input list, which one you used?

fabiodl:

All inputs still work (the image comes out fine), but it is vertically shifted down.
The menu is shifted in the same way.

Ian.M:
Later model Sony CRT monitors and TVs have auto white balance, performed by measuring the individual R, G and B electron gun beam currents (to control for decreasing emission) on three scanlines during the vertical blanking interval. If the vertical timebase circuit is faulty, its not uncommon to see them on screen.

It is *EXTREMELY* unlikely to be caused by damage from a possibly faulty console, and the only possible way that could happen and still leave it capable of showing a synced stable picture would be if the console used a frame rate right on the margin of what the monitor could accept, which could have over-stressed an already weak and failing vertical output stage.  If it had input stage (or input selector) damage, it would have problems displaying one or more colors and/or if the sync inputs were damaged, the picture would either be unstable or blanked.

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