nfg.forums

I have a CZ-600C which had issues with failing tests for Text RAM (VRAM) that I repaired. Thought notes might be useful, since I found basically no info about doing this online, so had to research this a bit myself

Repair for Graphics VRAM should be exactly the same.

A more indepth writeup with pics is at: https://buffis.com/repair/sharp-x68000-vram-repair/

Some TL;DR takeaways that I could not find info about online:

• IC1-IC16 on graphics sub-board is Text VRAM
• IC17-IC32 on graphics sub-board is Graphics VRAM
• All VRAM chips are MB81461-12 (x68000 has 32 of these)
• Donor VRAM IC's can be found on Mega Drive (2 per unit)
• Figuring out which IC is bad can be done by looking at the bad address range, bit error mask and x68000 schematics. I should probably write something about this up in more depth later.

That's great stuff, thanks for sharing it.