HW-Question, 9401-150 and System Password

Hello,

recently one of my 150 died. It got stuck in some screen and I wasn't able to open another session. LCD stated SCSI-related errors and eventually it recovered to a state that I could log in again and check the sst log. Some SCSI error.

pwrdwnsys, reseated all connectors. IPL not possible. See https://leela.pocnet.net/~poc/Nibbler-IPL.mov

As I understand, some early basic assurance test of the service processor fails. The "03" in between shows a reset and the last SRC 6756BE00 is completely unknown to the net. The SP did not even manage to spin up the disks, eventhough I see a single activity on the Bus, maybe an initial SCSI BUS RESET.

SCSI devices are OK. The same IPL sequence stays if I unplug the SCSI-Bus completely. Comparing with a second 150 with an unplugged Bus, the sequence is completely different. So I think, devices are not the problem.

I swapped the mainboard between these two and the error stays. So either it's a problem with the PSU or with the LCD-Board. Since 5V and 12V measure OK, I suspect the LCD board as culprit.

Sorry for the long introduction but I wanted to show that I've most properly isolated the fault. Now to my question:

I know that these machines have a system password which is generated by machine type, serial number and other stuff. Does anybody know what triggers an invalidation of this password? And where it is saved? I got a partly scrapped 150 for replacement parts. I don't know if I should replace both main- and LCD board and hope that this will retain the system password or if I'm doomed anyway to bug IBM to generate a new password for me for a 20 year old box. :-)

Thanks!

:wq! PoC

PGP-Key: DDD3 4ABF 6413 38DE - https://www.pocnet.net/poc-key.asc