Macintosh 512 vertical lines

[mattpnew]

Hi all, I recently found an old 512k logic board, which was dead; tested it in a working machine, so AB and CRT are perfectly fine.

- Cleaned it - still dead
- Replaced the caps - still dead
- swapped out the ROMS - signs of life but with a sad mac
- replaced a single RAM chip based on said sad Mac code

Now, I have vertical lines, so I am at a loss as to where to look next; any help would be appreciated before desoldering parts one by one, trial and error.

I would add that it will start to boot but eventually does freeze up.

Cheers