80 column card fault

[Preppie]

I got an 80 column card and it's displaying garbage, machine is fine via standard video out.

Any ideas what could be wrong?

20220906_192036.jpg (3.49 MiB) Viewed 13237 times

[Preppie]

I cleaned the contacts a bit, which were filthy, and now I'm just getting a black screen

[MikeDHalliday]

Have you tried pushing down lightly on all the chips? Could be dry solder joints causing the errors.

When this happened to my Einstein (Without an 80 col card), replacing the video memory cured the corrupted display.

Also, clean all the 8 col board with IPA and let it dry, could be some residue causing the issue.

[Preppie]

A quick clean resulted in black screen instead of garbled (not sure if that's a good thing or not). I'll give it a proper clean tomorrow and check the board over. 3 of the chips are socketed so i'll reseat those.

Just thought it might be a common problem (although nothings common with Einsteins) that had an easy answer, although not expecting an easy fix.

Will see how it goes tomorrow and updates you guys.

[Preppie]

A good clean and reseating chips hasn't helped. I guess the next thing is to grab a magnifying glass and check and reflow any suspicious joints.

Or maybe it could be the actual pipe connection on the motherboard, I guess that will need checking too.

[gunrock]

I second Mike's diagnosis, looks like some of the memory chips or multiplexer have failed.

[Lardo Boffin]

I have one doing similar (https://www.tatung-forum.co.uk/viewtopi ... rt=40#p670) but have a working one (get me!) so have not done anything with it yet. It worked for a while after cleaning it but stopped working again.

[Preppie]

Update on this:

I don't know much about electronics, I can solder stuff if I know what's wrong but that's about it.

Anyway, I got a working card yesterday so I tried swapping the socketed chips. The eprom, sram and CRT controller were socketed on one board but the CRT controller wasn't socketed on second board so just swapped the eprom & sram RESULT!

The old board is now working I tried just swapping one chip but it appears they're both bad. Not a problem, both chips are relatively common and inexpensive. I'll have to dump the ROM and write it to the new eprom but I'm guessing that shouldn't be too difficult and the eprom writers are fairly cheap (plus I'll likely need one for future projects).

Today I'm a very happy man

[gunrock]

Great work!

[Lardo Boffin]

Nice! I must fix my dodgy one at some point.