On Mon, 23 Jul 2012 20:13:41 -0400, Brad Thompson
<brad.thompson@...> wrote:
On 7/23/2012 6:05 PM, keithostertag wrote:
I am just now getting around to looking at my 7A13, bought on eBay
awhile back. I've never used a differential amp. Serial # B236701.
<snip>
I thought I'd show you a cap I found which has visible leaking (C505):
Hello, Keith and the group--
That's a so-called "wet slug" tantalum capacitor. Its clear outer
jacket is yellowed, likely due to overheating.
IIRC, the electrolyte in the wet-slug capacitors is sulfuric
acid, so when you remove the failed capacitor, I'd recommend
swabbing the corroded area with a weak baking-soda solution to
neutralize any remaining acid, followed by swabbing with
distilled water to remove any chemical residues.
Inspect for corrosion damage to all PC-board traces in the area
and repair as necessary.
Wet-slug caps don't like to operate with a reverse bias and
are likely to fail prematurely, so check the circuitry
for upstream component failures that might have back-biased
the capacitor.
73--
Brad AA1IP
It is part of the +50V input filter. The identical type and value
C553 next to it is part of the -50V input filter. In both cases, a 50
volt capacitor was used at 50 volts but maybe wet slug tantalums do
not need to be voltage derated?
I have seen Tektronix not derate capacitor voltage before.
David Hess