[ARC5] BC-348M

[Bill Cromwell]

On 12/20/2013 12:43 PM, Dennis Pharr wrote:
> I am also currently trying to restore a BC-348P model and I have the exact
> same problem - a short across the B+ line.  I suspect the issue is a shorted
> cap as well.
>
> Also, while tracing the wiring I've noticed a very odd thing - one of the
> six "canned" .5uf 250V caps (39-1) has buss wire shorting the terminals.
> The buss wire shorting the cap appears to be "as-built" since the pictorial
> wiring diagram also shows this cap as being shorted.  I can't understand why
> the designers would include a large canned capacitor in the design and then
> specify it as shorted in the documentation.
>
> If it was a last minute design change (possibly during production runs), you
> would think they would modify the design and leave out that Cap on
> subsequent production runs.
>
> It just seems to be a very odd thing, but maybe I'm missing something.
>
> 73
> Dennis
> WD5JWY
> Oklahoma City
>
Hi Dennis,

I don't have a BC-348 of any flavor. I do have some mil surplus radios 
and I have dealt with "can caps". Does your cap have the terminals 
shorted to ground or to the can by that buss wire or does it have 
terminals shorted together so that two sections of the cap are in 
parallel? Many to most of the "can caps" I have dealt with contain more 
than one cap, each with a separate terminal. The electrical common is 
the can itself and THAT is what is usually grounded. I'm redoing a 
Heathkit DX-100 and the can in the low voltage plate supply filter has 
exactly what you describe for two of the three caps inside.

I don't recall seeing that on the smaller couping and bypass "can caps" 
but most of them have multiple sections. Paralleling then, of course, 
adds the capacitance of each to the total capacitance. I don't know if 
that's what you have but combining the caps in parallel is the only 
thing that makes any sense to me.

73,

Bill  KU8H