A4000 repair troubles only 1M chipmem - Page 3

glenn · 08 May 2018, 21:07

Some of the chips I have ordered is waiting for me to pick the up at the post office (i.e ICA) now, then i will swap some IC's and see if it helps.

glenn · 11 May 2018, 02:50

Hmm, I replaced all electrolytic capacitors on the card, and after that it didnt boot at all in diagrom.

I added a fastmem SIMM and now it boots with serial output, "no chipmem detected"

If I do a manual edit of the chipmem area i can see that if I try to write for example FF to an area I get this instead..

$00000010 FF FF FF 01 FF FF FF 01 FF FF FF 01 DF FF 00 01 :
$00000020 FF FF FF 01 FF FF FF 01 FF FF FF 01 FF FF 00 01 :

Very repeatable..

I wonder what I accidenticaly did while changing caps ? ..since I cleaned the card from the leaked caps I might have destroyed some line..

Kin Hell · 12 May 2018, 00:36

Upmost respect for you guys going to these "Scope" depths.... Sincerely.

Multi-Layer 32Bit Circuit Boards (Four on the A4000 I believe - Pls don't strike me down...) ....with Acid erosion....

....You've probably done nothing wrong at all.

glenn · 15 May 2018, 11:58

Actually the A4000 motherboard is fairly easy to work with, only 4 layers (i.e 2 layers except ground and +5V), "big" components (1206 resistors, mostly PLCC IC's) and fairly high quality.

Anyway, I tried to trace a lot of connections without finding any problems.. BUT, I realised that diagrom sometimes find RAM, sometimes 64k, sometimes 96k ?? ..and when it does, I can test it ok ?

11 May 2018, 02:50	#42
glenn Repulsive Join Date: Nov 2015 Location: stockholm Sweden Posts: 89	Hmm, I replaced all electrolytic capacitors on the card, and after that it didnt boot at all in diagrom. I added a fastmem SIMM and now it boots with serial output, "no chipmem detected" If I do a manual edit of the chipmem area i can see that if I try to write for example FF to an area I get this instead.. $00000010 FF FF FF 01 FF FF FF 01 FF FF FF 01 DF FF 00 01 : $00000020 FF FF FF 01 FF FF FF 01 FF FF FF 01 FF FF 00 01 : Very repeatable.. I wonder what I accidenticaly did while changing caps ? ..since I cleaned the card from the leaked caps I might have destroyed some line.. Last edited by glenn; 11 May 2018 at 03:09.

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08 May 2018, 21:07	#41
glenn Repulsive Join Date: Nov 2015 Location: stockholm Sweden Posts: 89	Some of the chips I have ordered is waiting for me to pick the up at the post office (i.e ICA) now, then i will swap some IC's and see if it helps.

12 May 2018, 00:36	#43
Kin Hell 0ld0r Git Join Date: Mar 2009 Location: Cornwall, UK Posts: 1,570	Upmost respect for you guys going to these "Scope" depths.... Sincerely. Multi-Layer 32Bit Circuit Boards (Four on the A4000 I believe - Pls don't strike me down...) ....with Acid erosion.... ....You've probably done nothing wrong at all.

15 May 2018, 11:58	#44
glenn Repulsive Join Date: Nov 2015 Location: stockholm Sweden Posts: 89	Actually the A4000 motherboard is fairly easy to work with, only 4 layers (i.e 2 layers except ground and +5V), "big" components (1206 resistors, mostly PLCC IC's) and fairly high quality. Anyway, I tried to trace a lot of connections without finding any problems.. BUT, I realised that diagrom sometimes find RAM, sometimes 64k, sometimes 96k ?? ..and when it does, I can test it ok ?

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