Video Output Issues due to PSU

[jurassicman]

I guys,
I recently found out that using one of my Power Supplies (the black one that came on the A1200) I get a bad image on video.
More precisely an image with a lot of horizontal lines.

This PSU has already been recapped a few years ago and I tested the output values and they are good. I visually inspected the PSU and I did notice a few green spots near some resistors (R21 - R22 - R23 - R31 - R33). They were also in a bad shape so i replaced them but I didn't solve the issue.

Any ideas about which component could be the cause of the horizontal lines?

[pandy71]

Even if average voltage at the PSU output is OK (within limits) then noise+ripple may be beyond spec and beyond circuit filtering capabilities. You should verify this also.

[derSammler]

I would start by giving it a good clean. The area right of C13 looks gross. Dirt can be conductive and cause current to leak.

Are you sure it was recapped? Why on earth was it not cleaned during that?

And resolder the wires. If they are all as bad as the white one, it's not good...

[jurassicman]

Thanks both, guys, for the tips.

I'm sure it has been recapped (on the back the solder joints of the capacitors are newer than those near them and the capacitors look quite new as well) but certainly it hasn't been cleaned...

I cleaned the PCB with isopropyl alcohol and replaced the resistors R21 - R22 - R23 - R31 - R33. I also resoldered white and brown cables but I still have the video output issues.

I read something on the Net about noise and ripple but I don't understand what I have to check... sorry, I'm not a technician and my electronic knowledge is limited (and also my soldering skills are those of a hobbyist).

[pandy71]

To check Noise+Ripple you need to have very fast voltmeter - usually it is oscilloscope.
Electrolytic capacitors even new - replaced may have incorrect ESR and it may be unsuitable to be used in switched power supplies.