[Milsurplus] BC-348-Q Capacitor Testing

[Mark K3MSB]

I would like to keeps the inside of my BC-348-Q as stock as possible, so I
don’t want to replace caps if I don’t need to.


The tubular bypass and coupling caps are of the aluminum cylinder variety,
as shown below:


http://www.k3msb.com/temp/bc348q_underside.jpg


>From previous discussions about the BC-348-Q it seems that these types of
caps do not always need to be replaced. Instead of unsoldering each one, I
think this can be done by considering the entire circuit as composed of
several individual circuits separated by the various switch positions as
shown below:


http://www.k3msb.com/temp/bc348q_caps.jpg


My testing will conducted with the Dynamotor and tubes removed and the
AVC-OFF-MVC Switch in the OFF position.

I plan on using my IT-28 Cap tester in "Leakage" mode as it provides
current limiting.  I’ll probably use a series millameter as well.

So, here’s my proposed tests:

Test 1 - Inject voltage into relay pin 6 to test caps on the Blue circuit.

Test 2 - Inject voltage into relay pin 2 to test caps on the Red circuit.

Test 3 - Inject voltage into non grounded end of 61-7 or 61-6 to test those
two caps in the AVC circuit (Yellow).

Test 4 - Caps 61-9 (near 28V input) tested individually

Test 5 - Caps 63-2 (Audio Bypass) tested individually

Test 6 - Cap 61-8 (Audio Filter, Relay Pin 1), needs to be unsoldered to
test.

Test 7 - Cap 61-1 (RF Module), needs to be unsoldered to test.


I want to make sure I won’t inadvertently damage anything…….


Comments welcome.


73 Mark K3MSB
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