PDP 11 gear finally moved

Jay Jaeger cube1 at charter.net
Fri Jul 17 16:10:55 CDT 2015

What I am wondering about, though, is the extra current they draw while
they are forming up while the power supply is running.  The capacitor
might survive it (not get so hot that it fails), but the things supply
the higher than ordinary current to it might not.  Killed a bridge
rectifier on a PDP-12 that way.


On 7/17/2015 1:31 PM, tony duell wrote:
>> It is generally a good idea to re-form electrolytic capacitors in power
>> supplies, and to bench check the power supplies (under some kind of
>> load) before actually applying power to the whole unit.
> I am not sure either would have done much good here. The OP said it
> ran OK for an hour or so, when you test a PSU on dummy load you 
> typically do it for a lot less time than that, Incidentally, DEC PSUs
> of this type run fine with no load in my experience
> Also I have found the capacitors in these units to be very reliable. They
> can fail, of course, but virtually all the DEC bricks I have are on their
> original capacitors. I think I've replaced more chopper transistors than
> capacitors in these.
> -tony

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