ATARI ABC 286-60 (NOS) dead

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Hello, I got an ATARI ABC 286-60 PC (80286-16. 286 NEAT chipset, 1 MB RAM, onboard VGA, 60 MB RLL drive) as new old stock. But it's dead. When power up, nothing happens on screen. Powersupply seems to be Ok, power LED lids up, RLL harddrive spins up and initializes.

What I tested:

1. reseated all socketed chips, no change

2. put in a port 80h POST diagnostics card:

When starting then, the display on the 80h card changes from 00 to 03 and then it stops

3. pull out the SIPP memory modules.

When starting then, the display on the 80h cards changes from 00 to 03 and then it stops. But now it beeps dit ... dit dit dit ... dit ... dit dit dit ...

I found one memory module with the last pin bended away (30), fixed that, but no change when all modules reinstalled.

Remark: CMOS battery should be dead, but technically similar ATARI PC 4 (Also NOS, MITAC version, different mainboard, same chipset, starts posting fine with empty battery)

- ATARI ABC 286: http://www.atarimuseum.de/abc286.htm (photos inside)
- ATARI PC4 MITAC version http://www.atarimuseum.de/pc4m.htm (photos inside)

 

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Update. I have tested the ABC with the memory modules from the MITAC, same behavour.

But then, when populate all 8 SIPP sockets, it starts. So I wonder how a new old stock sealed computer can have wrong memory population. You can see the same memory population in one of the pictures on atarimuseum.de website, only the four last sockets are populated. But that is wrong. It has other memory population rule, maybe only every 2nd socket if only 4 SIPP modules installed. I have to RTFM and get addionally 4x 256kB SIPP.

 

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I know the problem now. SOme contact problems with the SIPP sockets. I have to fully dismante the machine and check the solder points of the sockets and so on.