8 Apr
2009
8 Apr
'09
3:28 a.m.
I think the +15 feeds all the regulators. It is regulated by a 54-09730 or
something like that. It's located in the high front of the H742 by the small
muffin fan.
I hope this helps. Also, the 11/40 has a lot of jumpers that have to be set
for the options you have(KW11, KE11, stack limit, FIS, etc). I know everyone
says to check power on the backplane, and not the molex, but now you know
why this is not always the way to go. Sorry, I don't have prints handy
On Tue, Apr 7, 2009 at 7:24 PM, Josh Dersch <derschjo at mail.msu.edu> wrote:
So I'm now the proud father of a DEC PDP 11/40,
which should be a fun
project/adventure to get running again.
I have been testing out the power supply and everything looked good this
morning, at which point I figured I'd populate the CPU backplane and see
what would happen. The answer is: not much -- occasionally a few LEDs would
light up, but the machine was completely unresponsive.
I went a bit further and tested the voltages at the backplane, and while
checking the +15V, my probe slipped momentarily, bumping a nearby wirewrap
pin, causing a small spark. Now, where I once had +15V, I have 0V. And
since the -15V regulator is powered (in part) from the +15V line, that's
dead too.
I was hoping, after reading through the documents again, that it would be
something as simple as fuse F1 on the power control board, but no such luck.
The fuse is still good.
Any suggestions for what's most likely to have blown when I screwed up
here? Any recommendations for working on this supply? I'm really looking
forward to pulling this thing out of the rack to work on it -- this thing
looks heavy :)
Thanks,
Josh (still slapping himself for screwing this up...)