First post, by abrunetto
Hi Folks! I am trying to restore to a working condition an IBM PS/2 model 80 with a planar type 3 (yes, japan designed).
Everything seems to be in good shape, but unfortunately I am facing a (very) tricky issue, the ones that I love.
So, I am able to POST the machine just when it is cold, and one out of 3 to 5 tries. When it POSTs, the SCSI HDD boots with a shiny MS-DOS 6.00 (just command.com and the hidden files), and the machine hangs about 30 seconds after.
Then, if I power cycle, I only get the (in)famous black screen (no beep, no POST messages, no blinking cursor, no orange LED, no nothing), just BLACK screen.
Sometimes. if I removed the RAM module (4MB) I get 211 memory error, which seems to be fine. If a install the memory on the second memory bank I get 215 error code, which also seems to be fine.
Sometime, when it POSTs the memory counts 3712 with 201 and 164 error. The right amount of memory is 3968, with no errors at all.
PC Speaker is working fine, as well as the 3v battery.
The 5V, 12V and -12V power rails seems to be estable, but the power good signal is around 3.73V.
I don't know if 3.73V is within power good tolerance (should be 5v).
I power on the psu alone, wait several minutes and then plug it in on the motherboard, and power on again. If the motherboard was cold, it has the same behaviour as before, with a "cold" PSU.
Any help would be very appreciated.
Best Regards,
Ariel