PDP 11 gear finally moved

Tothwolf tothwolf at concentric.net
Sun Jul 19 20:53:43 CDT 2015

On Fri, 17 Jul 2015, Jay Jaeger wrote:
> On 7/17/2015 1:33 PM, Rich Alderson 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. The rest of the advice is sound.
> Replace - no, I don't agree - especially not for those of us who don't
> have the kind of budget that your organization has.  In my experience,
> for equipment of this quality and vintage, 95% or more of the time an
> hour to a few hours of re-forming is all that is necessary - and as Tony
> has pointed out, even that is not often really necessary.

Replace - yes, *especially* if you don't have a big budget. Aluminum 
electrolytic capacitors are CHEAP and easy to obtain. Replacement 
semiconductors by comparison are expensive and can be quite difficult to 

While it might be worthwhile reforming a special purpose NOS electrolytic 
that isn't much older than 15-20 years old, reforming 20-30 year old 
heavily used (read: past usable service life; evaporation of the 
electrolyte, corrosion of the foils and especially foil to terminal 
junctions, etc) is a complete and total waste of time.

Ironically, 20-30 years ago this same mindset used to persist with people 
who collected vacuum tube (valve) based radios and television, however 
that attitude no longer seems to be present in those communities today 
(not worth risking an irreplaceable transformer or inductor over 
$5.00-$10.00 worth of aluminum electrolytics).

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