exxos's Atari, Amiga & retro forum

Hello there!

My 1040STFM has a strange issue. After switching it on the screen shows almost immediately as in the attached picture. After some time a reset will yield a completely white screen, so temperature plays a part in this. This phenomenon is reproducible. As you can see on the second picture there where some issues at some point in history with the ram memory. I assume this was fixed in the factory: the machine was sealed when I bought it. They did a sloppy soldering job though, looked like some pins weren't attached to the motherboard at all. A small miracle this has ever worked.

I reseated all socketed IC's, soldered ram decently, measured connectivity on all pins of the two rom ic's. No difference. Unfortunately I don't have a scope or logic analyzer, but with some clues as what to check I will go see a friend with decent equipment. I suspect the memory IC's, but I'm not sure.

What could be the issue, and what is wise to check?

Thanks in advance!
Vic.

That screen looks very much like you've got a RAM problem.

I'd tweak the PLCC sockets for the MMU and GLUE using this guide: PLCC Contact adjustment as sometimes cleaning is not enough.

Ideally I'd suggest a diag cartridge and a serial connection as they are pretty good at revealing which bits are problematic, but I'd also suggest either feeling the RAM/MMU/GLUE for what's getting hot or using freeze spray one RAM chip at a time, and if that makes no difference, freeze spray the MMU then GLUE to see if that helps.

If you reset between each freeze then you may get a different result.

If you have a friend with good kit then check all the clocks are good wherever they need to be and that /reset and /halt are not doing anything odd, do continuity checks of the address and data lines, check for stuck bits on address/data lines and make sure cas/ras lines are behaving as expected.

I'd also recommend using a bench PSU to provide 5v for testing in case the PSU is iffy.

Good luck.

Thanks for all the advice, will do!

Cheers,
Vic