[NJARC] BC-348

[Scott Roberts]

Hi Everybody-
I am messing about with my BC-348P(Not my Uncle's, but the one I picked up at the swap meet a few months back) and am setting it up for its original power supply. Dave Sica did me a great favor, and swapped me a BC-348 dynamotor and mount in exchange for a radio I had he was interested in. I cleaned & relubricated the bearings on the dynamotor, and put it into the de-modified chassis after testing. My test rig is simply a 25.2 VAC transformer, rectified through 4 1N4007 diodes, but no filter caps. (This tuning units, see nothing may be important...)

The dynamotor tested out nicely- on 25.2 VDC(rectified) it was putting out around 230 VDC. The few caps in the dynamotor are original, one a nice metal one, the other a paper cap. (It is a DM-28-Q, from a BC-348-Q) Caps have not been replaced in the dynamotor, but all caps were redone in the BC-348-P.

When I switch the unit on, in either AVC or MVC mode, with the proper impedence headset, or speaker, I get a hum, but no indication of volume control- no scratchiness, nothing, but a hum. I have tried running it through the FL-30-M filter(similar to FL-8-A) but it has no effect. Could this be a hum from my cheap-a** power unit(literally thrown together to form a circuit) that could be solved by a couple filter caps before it comes into the radio?(If so, would 47/450Es be about right?)

I have been rechecking my wiring repairs, and, other than tearing out the tuning units and looking into them I see nothing obviously missed. Tubes have all been tested on my Precision tester, and check out fine.

Ideas?

Thanks!
Scott