[R-390] Tube longevity

[Tim Shoppa]

> turning off the plate voltage by switching to stand-by will cause the
> plate voltage to raise excessively, and can cause some caps to blow.

In some industries part of regular maintenance is to "margin" the power
supplies up and down just to find (and in some cases blow up) the weak
parts.

Blowing the weak parts up is an added bonus - it makes sure that nobody
will try to re-use them!

I'm thinking mainly of the original electrolytics and black beauties,
although I'm sure some of the metal-can Westcaps/Vitamin Q's and yellow
Aerovox-type caps will blow too. Some of us hate old crappy caps with
a vengeance. (Or not-so-crappy-originally-but-now-50-years-later....)

We're probably the same guys who stuck electrolytics across 120VAC
to watch them blow and now hold titles like "Director of Destructive
Testing"!

Tim.