PVM 20M2U salvage (Hula/flag problem)

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Hello. I got a dead PVM 20MU and am in the process of bringing it up to life (hopefully). I Re-caped the A board with caps from Savon-Pat, and that made I at least get image (before I used to get a red tally light). Now I am getting image but I have a slight hula/flag weaving problem as you can see on this 11 seconds video: https://www.youtube.com/watch?v=0vE4S1msUP8

I read somewhere that it may be related to some problem on the 115V output of the PSU, since I don't know what can have happened there I tried a re-cap for the capacitors around the voltage regulators, but that doesn't seem to change anything. I got those measurements on the CN605 (that connects the PSU/G Board to A board)

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15V  = 15.07V
115V = 119.6V / 121V (no load)
-15V = -26.9V / 26V (no load)
5V A = 4.822V

No load being measuring with CN605 disconnected.

A visual inspection doesn't show anything specifically burnt or exploded, so I am guessing that it must be something else. I am going to bring the monitor to a separate table where I can do measurements with the board out of the case so i don't short anything, but I would love to know if anyone has seem this problem and where's a good spot to start looking. It even may be not a G board probolem at all, or maybe I have to regulate something after the recap that I don't know. Anyway, those voltages are strange, at least. I don't have an oscilloscope that can get to 115V to check the waveforms there unfortunately.

Thanks for any help! The 20m2u service manual can be found here https://archive.org/details/SonyPVM20M2 ... viceManual

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Ok so I did some other measurements today and I noticed that the voltage difference goes all the way to the D601, the main rectifier. Pins 2-3 are the AC in and are correctly at 125V/Wall AC as one expected, but between 1 and 4 I get 131.8VDC, and if the notation on my manual is correct, it should be 110V



Out of curiosity I also measured pins 1 and 4 of T603 and I got the same measurement. Now what I want to know is if that voltage is wrong because the diode is bad, or is some of the components after the diode pin 4 that are supposed to regulate that voltage down and is not. I guess it's time to re-learn how rectifiers work.

Anyway, will post more if I find something.

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Turns out the STR-S3115 that is responsible for the 115V output was busted. Pins 1 and 2 were shorted, so basically there was no voltage regulation happening there. I replaced it with one that I found on ebay and that solved all the flag/hula problems and now the PVM works perfectly.

[LordKirkis]

Thats amazing. Really goad you managed to repair it. Do you have an update on how its currently running? Have you ran into any other issues with it?

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Thats amazing. Really goad you managed to repair it. Do you have an update on how its currently running? Have you ran into any other issues with it?

I sold the PVM a few months ago, but AFAIK it's still alive and kicking perfectly on its new home