[R-390] Depot Dawg / Capacitor leakage test

[Bill Smith]

Here is a test I use with the Simpson 370 VOM (what else is there to use
with an R-390, or any other receiver, for that matter!).  It is only a
9-volt test, but works well to identify obviously bad caps.

1.  Switch the meter to measure x 10,000 ohms (high ohms scale).

2.  Put the meter leads across the capacitor (must be at least .01 mfd. or
greater value, out of circuit, or in a dead-end circuit).

3.  Watch for a "kick" as the capacitor charges.  If the capacitor is leaky
at 9 volts, some resistance will be indicated.  Of course it is worse at
higher voltages.

4.  Disconnect one probe, wait a second or two and connect the probe again.
If the meter kicks again, even slightly, internal capacitor leakage has been
enough to discharge the capacitor.  It is likely bad at higher voltages.

5.  This is a quickie test.  Best test is at the rated voltage of the
capacitor, but the VOM test can save a lot of time.  If it fails, the
capacitor will always fail the high voltage test.

6.  I am not sure tests are all that valuable.  I have had sets work well
for the first several hours, then capacitors have deteriorated.  With few
exceptions, if I suspect caps are bad, out they go.

The Vitamin Q caps in the R-390 are one of those exceptions, they seem to be
holding up fine.  Unless manufactured within the last twenty years or so,
oil (bathtub) capacitors, however, are now going bad.  Have a GR Wave
Analyzer with 21 of them.  :-(

73 de Bill, AB6MT
billsmith@ispwest.com

----- Original Message -----
From: "Rodney Bunt" <rodney_bunt@yahoo.com>
To: "Drew Papanek" <drewmaster813@hotmail.com>
Cc: <r-390@mailman.qth.net>
Sent: Wednesday, August 28, 2002 6:45 PM
Subject: [R-390] Depot Dawg / Capacitor leakage test


> The maximum voltage would be the "battery" inside the DVM say 9v. Only a
really bad 200v capacitor
> would leak at 9v !!!
>