PDP 11 gear finally moved

Tothwolf tothwolf at concentric.net
Sun Jul 19 21:15:48 CDT 2015

On Fri, 17 Jul 2015, 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..

No. It is because the typical aluminum electrolytic capacitor at 20-30 
years old is simply past its useful service life. At that point they tend 
to suffer from all sorts of issues and can no longer be considered 

That whole "botched industrial espionage" thing is also somewhat of a 
myth. There have been at least 3 different cases where there have been 
industry wide problems with aluminum electrolytics.

The earliest I tend to see are the first generation SMD aluminum 
electrolytics from the late 1980s to about 1993. Those have problems with 
their rubber seals due to the rubber compound breaking down either due to 
the temperature they were reflow soldered at or because the boards were 
cleaned with chlorinated solvents. Newer SMD aluminum electrolytics do not 
have this problem (and capacitor manufacturers explicitly warn against 
using chlorinated solvents to clean pc boards).

The second were those which you are referring to above, aka the "capacitor 
plague". Those started showing up in the marketplace around about 2000 and 
were mostly gone by about 2005.

The third were the ultra-low ESR types from certain major manufacturers. 
The most common I dealt with were Nippon Chemicon KZG and KZJ (all of 
them, replace them wholesale on sight) and a batch of Nichicon HN and HM 
(only a certain date range were affected). The Nippon parts are of a 
faulty design (which Nippon never would admit to it, instead they tried to 
wipe all data about them from their site) while the affected Nichicon HN 
and HM parts were supposedly just overfilled with electrolyte (according 
to Nichicon).

> 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

I don't know how much equipment you service, but equipment made in the 80s 
pretty much needs replacement aluminum electrolytics today if it has many 
hours on it and/or it needs to remain reliable. I have a number of early 
'80s monitors and PSUs currently in my repair queue which only need 
replacement electrolytic capacitors (distorted picture, excessive ripple, 

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