PDP 11 gear finally moved

Jay jaeger cube1 at charter.net
Sun Jul 19 23:31:41 CDT 2015

Well, all I can say is that my experience differs.  I have had newer capacitors fail, and old ones, too, of course, but nothing points to wholesale replacement as a cost or time effective strategy, especially on something like an Altair.  FWIW, I don't run my vintage machines all that often.  Of course reforming a bad capacitor, whatever the failure mode, is going to be useless.

Tothwolf <tothwolf at concentric.net> wrote:

>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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