On Thu, 27 Apr 2017 14:29:07 -0700, tabbypurr wrote:

I have an old EHT PSU to repair. There are 2 capacitors, one paper, one
plywood! The paper cap, which is uncased, tests as: 420nF 11 ohms ESR,
5% loss. I've not yet done a dc leak test, which it needs. What do you
think of those figures? IME pre-war paper caps are highly suspect. I'd
rather establish what I can before subbing it, as the construction of
the whole thing is rather characterful.

I've a few boxes full of oil/paper metal-cased capacitors I could test
for comparison purposes if needs be, Tabby, but I've added s.e.r in case
some kind soul there will know the answer off the top of their heads
first.

On Thu, 27 Apr 2017 14:29:07 -0700, tabbypurr wrote:

I have an old EHT PSU to repair. There are 2 capacitors, one paper, one
plywood! The paper cap, which is uncased, tests as: 420nF 11 ohms ESR,
5% loss. I've not yet done a dc leak test, which it needs. What do you
think of those figures? IME pre-war paper caps are highly suspect. I'd
rather establish what I can before subbing it, as the construction of
the whole thing is rather characterful.

What, if anything, are the markings on the caps themselves?

You ought to be able to screen a modern film cap to within a very few percent of the OEM values, go high on the voltage parameters, and go from there.

Peter Wieck
Melrose Park, PA

Depends which war..

On Friday, 28 April 2017 19:58:41 UTC+1, wrote:
On Thu, 27 Apr 2017 14:29:07 -0700, tabbypurr wrote:

I have an old EHT PSU to repair. There are 2 capacitors, one paper, one
plywood! The paper cap, which is uncased, tests as: 420nF 11 ohms ESR,
5% loss. I've not yet done a dc leak test, which it needs. What do you
think of those figures? IME pre-war paper caps are highly suspect. I'd
rather establish what I can before subbing it, as the construction of
the whole thing is rather characterful.

What, if anything, are the markings on the caps themselves?

the cap doesn't have a case, let alone markings.

You ought to be able to screen a modern film cap to within a very few percent of the OEM values, go high on the voltage parameters, and go from there.

Peter Wieck
Melrose Park, PA

Of course I can replace it, and probably will need to, I just wanted to know if this thing might still be serviceable, if so I'll let it stay.


NT

On Sunday, April 30, 2017 at 6:53:02 PM UTC-4, wrote:

Of course I can replace it, and probably will need to, I just wanted to know if this thing might still be serviceable, if so I'll let it stay.

The short answer is No.

Peter Wieck
Melrose Park, PA