PDP 11 gear finally moved

Jay Jaeger cube1 at charter.net
Fri Jul 17 16:16:03 CDT 2015

I tend to agree with your hunch.

On 7/17/2015 1:55 PM, Todd Killingsworth wrote:
> 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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