[Coco] seeking for help...

[Camillus]

Hi, coco users,
Anyone can give some hints on how to repair a coco2 that has bad sync, did all the classic chip swapping to no avail. Scope images are close to what I found in coco2 service manual, but the device I have is a Korean made, so no correct schematics.
The coco powers up with a scrambled screen, I can see the square and some color stripes on the right side. Sometimes it comes up ok, even with BASIC logo, but after switching some ram and other Ic's the Basic does not show. Don't know I made things worse. Anyway got lost a bit so maybe some hints?
Thanks in advance