[ARC5] BC-348M

[D. Platt]

On 12/19/2013 10:43 PM, Tom Elmore wrote:
> I am in the process of bringing a BC-348M< back to life. Is it correct that
> pins 2 & 6 are the receiver muting when paired with a transmitter? It
> appears I need to short them together to provide B+ for some of the tube
> screens.  It also appears I have a short (probably a cap) on pin#2 somewhere
> in the chain.
>
>
> Thank You
>
>   
>
> Tom Elmore KA1NVZ
>
> Anchorage, Alaska
>
>   
>
>
Tom,

Looking at the book for the H, K, L, and R (which should be all but 
identical), Pin 2 is, of course, the high-side of B+ and pin 6 is the 
source for screen voltage for several tubes.  Looking at the book, it 
appears that there are several possibilities.  I have seen any one of 
these referenced caps hard-shorted, so its nothing new.
The caps in question could be:

48-2B  (Switch in AVC, only) Located on the primary side of the audio 
output circuit.
48-1A, 49-1A, 49-1B.  These are the metal caps in the cluster.  This 
group is the only one that has _3_ of the capacitor sections jumpered.

The balance of the B+ circuitry is resistively isolated and I would not 
expect a "hard" short to ground along any of those paths. If any of 
these caps have dead shorts, it will pull B+ down and really load the 
dynamotor, of course.

I hope these reference designators will jibe with your receiver 
schematic.  BTW, and if you don't already know, you'll need to install 
an accessible toggle switch across those pin to allow netting of a 
transmitter frequency.

Regards

Jeep - K3HVG