15 Nov
2006
15 Nov
'06
2:53 a.m.
Don wrote:
By first memory board I infer that you mean the MS11-M
M8722 256KB.
This board requires both +5V for logic and +-12V for the memories.
By second memory board I infer that you mean the MS11-P M8753 1MB.
This board is 5V only; it does not require either +-12V or +-15V.
I would have expected it to be the other way around (MS11-M
does not work but the MS11-P does) but hey. It could be a
stuck driver on the MS11-P that is pulling some memory/unibus
control signals to ground, hanging the bus and cpu.
Yes, correct!
I checked the voltages, they are all just fine. Phew!
I removed the M9302 in slot 14 a-b, and plugged the M9202 in it
to add the next backplane to the total system.
In that backplane is a TUK50, RUX50, UDA50 and the RL11.
Power on ... all is perfect, for what I could see in a glance.
We had a family visit, so I did not have much time, but as in a
miracle, the RL02 FAULT light remained OFF too!
One quick check: I installed the MS11-P in the 2nd memory slot.
Turn on the system ... yep, a hang condition and the FAULT light
on the RL02 goes ON immediately! Removed the MS11-P again, and
everything looks healthy!
It definitely looks like a defective MS11-P. The effect that it has
on the system (especially the RL02's FAULT light) gives me hope to
be able to repair that module one day!
thanks!
- Henk.
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