DIYbanter - View Single Post - Why should someone replace ALL the capacitors on old Tube equipment?

analogdial

wrote:

I have been reading alot of websites about caps. One of them said the
wax coated ones were less leaky (for moisture), than the old plastic
coated ones. I am referring to the ones called "black beauties", that
have color code bands on them.Yet, back in the early 70's, I knew a guy
who was a retired radio-tv repairman as well as a Ham operator, and he
used to say those "black beauties" were far better than the wax ones.
(as well as the other plastic encased ones with the numbers on them
instead of the color bands).

That's conflicting info. Yet I know that all of them are paper caps.

In my opinion, the Black Beauties with color bands on them are bad news.
Worse than wax dipped paper caps. They crack, leak oil and sometimes
fail hard -- short circuit. As far as I know, all the Black Beauties
with bands are oil filled.

I've seen old 50s magazines with full page ads claiming wonderful things
for the oil filled Black Beauties and it sure seemed like a good idea.
Steel can paper in oil caps are much more reliable than wax dipped
paper caps, why not paper in oil in a plastic tube? Didn't work out
that way, I don't know why. Maybe the plastic outgassed something nasty
into the cap. Some of the paper in oil Black Beauties had standard
numeric marking rather than bands. The paper in oil Black Beauties can
be identified by a soldered lead on one side of the cap.

The second generation Black Beauties were actually OK. They used a
mylar-paper dielectric which held up about as well as all the
advertising promised for the first gen Black Beauties.

But the damage to the reputation of the Black Beauty had been done and
the Orange Drop became Sprague's high end film cap.