Yellow screen with 1MB chip memory

[naujoks]

I have an A600 which shows me a yellow screen on boot with the 1MB chip memory expansion in. When I remove it, the computer boots and works just fine.

Is there any way to find out, which chip could be faulty, other than desoldering them one by one and checking them in a tester?

[SkulleateR]

Could be as well a bad connection, clean the contacts (both the mainboard and the expansion) with a soft pencil eraser and IPA after ... then reseat the expansion and be sure to pull it backwards a tiny little bit after that

[naujoks]

I've already cleaned it.

[SkulleateR]

Then maybe try to piggyback the ram with a working IC could be an option to determine the defective one, although that's not always working but it could be a start. Do you happen to have a picture of the expansion ?

[naujoks]

Can I attached images directly?
Hopefully this URL works: https://drive.google.com/open?id=1wv...u&usp=drive_fs

Due to the kind of memory ICs, it will be almost impossible to piggy back anything on to them.

[SkulleateR]

Sorry, don´t have permission to that files (google says) ... don´t think you can attach anything here, but you can use https://eab.abime.net/zone.php? to upload a ZIP file perhaps

[naujoks]

I'll try again.
It's those chips with the little legs that are tucked under the body.
https://drive.google.com/file/d/1wvE...ew?usp=sharing

It says 89X8922 on them. I can't find those ICs for sale anywhere though.

[SkulleateR]

Nice, that´s the same I got in one of my 600s

But yeah, they are hard to source in that SOJ-26 package format ... have you already tried to bridge the switch ? That was giving me a hard time while restoring mine !

And also be sure (mentioned that above) after installing it, pull it back a bit (maybe 2 to 3mm). Mine would not make good contact, even that I cleaned everything (more than once)

If that's not the fault and you really want those chips for testing, look for some 1MB Simms on EBay, sometimes they have such chips on there

[naujoks]

Actually, what's the purpose of that switch? I assumed it has something to do with the clock IC, but maybe not?

[SkulleateR]

Originally Posted by naujoks

Actually, what's the purpose of that switch? I assumed it has something to do with the clock IC, but maybe not?

AFAIK you can turn the expansion off with it as stated here -> Micro R&D: Pyramid A601

[supaduper]

Just buy a new 1mb ram expansion as they are cheap

https://www.ebay.co.uk/itm/165044387...1-KqgZA&edge=0

[lilwshu]

I used this guide to isolate failed chips on a RAM expansion https://www.jm27.de/repairing-an-a50...for-amiga-500/ but I used Amiga test kit to do the ram checks.