21 Oct
2021
21 Oct
'21
8:36 a.m.
No luck, there are no 12V traces continued to the edge connector, and
the 5VB goes to a three way jumper post where the jumper is between the
common and 5V
Besides, there are two LEDs on the board that light up, one red one green.
Thanks,
Nigel
On 2021-10-21 10:58 a.m., Chris Zach via cctalk wrote:
On 10/21/2021 9:10 AM, Nigel Johnson Ham via cctalk wrote:
Thanks, but like bitsavers they are all older
that the one I have.
To be honest, I never saw anything Plessey bigger than 128kB in the
wild, so I have to wonder what kind of machine this board came from,
although it was in a pile of Qbus things that I got the J boards from.
I'm thinking that maybe it was not sold separately, but an OEM build for
military etc, and perhaps it is jumpered to get power from memory - but
without the manual or tracing the lands I can't really tell.
Wait, that could be it: If the board is jumpered to power the memory
refresh/chips from battery then of course it wouldn't work without it.
Should be easy to check: Find the battery +5 and +12 pins on the Q bus
then use a tester meter to check from those pins to any of the jumper
pins. If you find continuity to a jumper that is closed you might have
identified the problem :-)