PDP 11 gear finally moved
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
> 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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