Need help with a BA11-K power supply

Julian Wolfe fireflyst at earthlink.net
Sat Oct 22 10:55:11 CDT 2005


Alright, I thought I would crosspost this to see if anyone here has one of
these modules.  I don't even need to look at this, I remember that the relay
does not kick on at all.  I have a DEC jumper that runs across the two molex
terminals on the back of this module that just plugs in.

So, that being said, does anyone here have any of these modules?  I know the
other 3 modules of the power supply are common replacements, so I'm hoping
someone saved a spare of these too ;)

If you've got one you want to part with, let me know!

Thanks
Julian

-----Original Message-----
From: owner-info-pdp11 at village.org [mailto:owner-info-pdp11 at village.org] On
Behalf Of Don North
Sent: Thursday, October 20, 2005 2:20 PM
To: info-pdp11 at village.org
Subject: Re: Need help with a BA11-K power supply

Julian Wolfe wrote:
> Well, I decided to take another crack at getting my 11/34 system 
> working again.  Currently I've still got some problems with it - 
> firstly though, the power supply.  It blew when I hooked one of the 
> front panel switches up to it, though nothing seemed to be wrong as 
> far as what I could tell from all the diagrams.
> 
> Right now the disassembled BA11-K box is sitting in my living room 
> taking up space.  Now, when the PSU blew, I was able to notice that 
> the spark came from what LOOKED like the portion that the power cord 
> comes from.I looked at the traces under a magnifying glass, and 
> couldn't see anything wrong, and I can't smell anything. I checked all the
fuses, those seem to be sound.
> 
> In any case, when hooked up to nothing, the fans don't even kick on.

On this box the fans are wired directly across the primary of the main power
transformer, so unless the fans died (both of them) it would indicate that
the main power relay circuit is not kicking in.

The K box has a power input circuit breaker on the back that needs to be 
   flipped to on (I'm sure you got this far) and then the power relay needs
to be engaged as well. The 11/34 console switch can do this (wires run from
the controller to the front panel switch) and it can also be done from the
rear 3pin molex connectors as well. Short pins 1-3 to engage the power-on
relay. This power circuit on module 54-13089 has it's own little power
transformer and a bunch of diodes and capacitors. If shorting the pins on
the molex (either one on the back will work, both are wired to the same
place) does not turn the fans on, or you don't hear the clicking of the
relay, then most likely the sparks that eminated from near the power cord
entrance (which is this power module) were from this board, and it likely
indicates blown circuitry (sparks are NEVER a good sign).

Hope this helps.

> Can anyone give me a test process I can go through to diagnose the 
> problem, or would anyone here be willing to look at the power supply 
> for me if I shipped it to them?
> 
> As it is, I have this dead machine doing nothing and my girlfriend 
> keeps pestering me about it every time she comes over because it doesn't
work.
> 
> In any case, I'd appreciate any help that could be given to me!
> 
> Thanks!
> Julian
> 
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