[R-390] Leaking C103?

[David Wise]

You are measuring it wrong, Barry.  The leakage current of
electrolytic caps like C103 is not proportional to applied
voltage - you can't express it as a resistance.  The fact
that you did suggests that you used an ohmmeter, which
probably did not apply more than a volt or two.  The cap
would have to leak at least a few mA to give the behavior
you observed*.  Suitable replacement caps (47uF/100V)
caps are abundant and cheap.  The easiest way to check the
original is to temporarily remove it.  This is feasible
because its only role is to keep the scratchiness of the
pot from blowing your ears out as you turn it.

73,
Dave

* I hope I'm not confusing threads.  Someone reported
unexpectedly high gain when RF GAIN was set to minimum,
and I replied that a possible cause was a leaky C103.

> -----Original Message-----
> From: r-390-bounces at mailman.qth.net
> [mailto:r-390-bounces at mailman.qth.net]On Behalf Of Barry
> Sent: Sunday, September 17, 2006 11:46 AM
> To: R-390-List
> Subject: [R-390] Leaking C103?
> 
> 
> Was checking the RF gain control last night and discovered 
> C103 (the 50uF
> bathtub cap) appears to be leaking (was reading about 500k 
> without the RF
> gain control connected.  I wonder if this is hindering the 
> operation of
> things?  I don't find what it's purpose is so not sure how 
> that would affect
> the operation.