Sanwa PM1723C, chassi for Toshiba Arcade CRT Monitor - sync problems!

[realp]

Hi all!

New here - lets see if someone can help me. :-/

Anyway, I have an arcade game with a Toshiba CRT screen. The chassi card (PCB) is a Sanwa PM 1723C. I have installed a cap-kit a few years ago, replaced the sync chip (Hitachi HA-11235) and replaced the Vertical Sync pot. I have also replaced two more caps just a month ago.

First I had problems with vertical sync. Then I replaced all above. Now sync is PERFECT for 20+ minutes. After that, the PCB probably gets too hot and the Horizontal sync messes up. First it just becomes "wobbly"/wavey on the edges, but soon it's just a complete chaos.

I'm attaching the schematics for the chassi. The two caps replaced that solved the vertical sync problem is C311 and C335 on the schematics.

If anyone knows what can cause the problem, I'd bery very happy! THANKS!