Sanwa PM1723C, loses V-hold when warm

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    • Sanwa PM1723C, loses V-hold when warm

      Hi, I'm working on a Sanwa PM1723C which loses V-hold when it has been running about 20 minutes.

      It all starts out ok, but after 5-10 minutes the image start to twitch a bit. And after 15 minutes the image starts to roll vertically.
      After 20 minutes it rolls so fast that I cant distinguish any graphics on screen.

      I've checked all solder joints around the HA11235 sync IC.
      I've replaced the V-hold pot
      All caps have been replaced.
      I've also socketed the HA11235 sync IC and replaced it with a known working one.
      No difference at all.

      Any pointers at what to look for?
      I'm going to buy one of those air-in-a-can so that I can flip it upside down and shoot some ice cold air onto some areas of the chassis handling vertical sync.

      I attached the schematics for this chassis as well.
      • pm1723c.jpg

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