PDP 11 gear finally moved

Todd Killingsworth killingsworth.todd at gmail.com
Fri Jul 17 13:55:38 CDT 2015

I suspect part of the "swap'em ALL out" mentality comes from the 90's when
some botched industrial espionage had some of the bottom-tier cap
manufacturers using a dodgy electrolytic formula for their caps.  These
caps would have a frequent failure rate..

While not an issue for pre-90's electronics,  it has fostered the mentality
of full replacement for 'newer' electronics i.e. arcade/pinball machines

Todd Killingsworth

On Fri, Jul 17, 2015 at 2:42 PM, tony duell <ard at p850ug1.demon.co.uk> 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.
> >
> > It is always a good idea to replace electrolytic capacitors in power
> supplies.
> Could you, please, explain why? And how often should this be done? Every
> week, every month, every year, or what?
> FWIW, the number PSU elecrtrolytics I have replaced can be counted on the
> fingers of
> one hand -- in unary. Well, perhaps both hands. But it's <1% of all the
> PSU electrolytic
> capacitors I own.
> Only 2 cases spring to mind :
> The PSU in my 11/44 had a high ESR capacitor on the +36V rail (all other
> caps in the machine
> were fine)
> I changed the 2 mains smoothing capacitors in my HP120 not because they
> were electrically
> defective (they tested fine) but because one was bulging a little on top
> and had it exploded it would
> have hit the neck of the CRT with all the problems that would be likely to
> cause.
> I do find this witch-hunt against capacitors to be curious, given how few
> I've found to have
> failed. I suspect a lot of it comes from audiophools who think this is the
> way to fix anything...
> -tony

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