BA11 power filter

Chris Zach cz at
Tue Jun 1 16:39:16 CDT 2021

Interesting: I just tried firing up a pair of BA11-N's to see if they 
work. One blew the fuse in that block in the back and I thought it was a 
shorted PS but the PS input caps are not shorted. I'll check to see if 
the filter capacitor in that spot is shot.

On 6/1/2021 4:16 PM, Steve Maddison via cctalk wrote:
> After a few years in storage I'm finally getting to play with my PDP-11
> stuff again. Figured I'd start small so rolled out the 11/23. PSU looks
> fine, pulled all the cards and checked voltages, no problem. Shortly after
> however, some magic smoke was released from the block in the back where AC
> comes in and the power switch is mounted. The only other thing in there is
> a big old line filter. Judging by the smell, I suspect a filter capacitor
> has given up the ghost. I'd check, but the whole thing is soldered shut so
> not exactly easily serviceable. Would I be correct in thinking such filters
> aren't entirely necessary and could just be bypassed? It looks like the
> manufacturer (JMK) is still going so a new replacement might not be out of
> the question. Whether I could find one with the same mounting holes etc. is
> another question I've not looked into yet.
> Cheers,
> Steve

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