[Milsurplus] BC-348-C Modifications

[Al Klase]

Hi Mike,

A couple of comments on the mods in that set:

The 6V6 is udoubbtedly an attempt to get more audio to properly drive a 
speaker.  The radio was intended to drive a whole B-17 full of headsets, 
but not a speaker.  The problem is lack of gain more than lack of 
driving power.  The real solution is to add another triode to drive the 
41, but lets not go there at this late date.  As the socket has been 
changed, I'd replace the 6V6 with a 6K6, the octal equivalent of the 
original 41, but it probably won't make a big difference.

The 6AC7 was a misguided attempt to achieve better noise performance.  
The problem is, it's a sharp-cutoff pentode, and will mess up the AVC 
action.  I'd surely replace it with a 6SK7, the single-ended (no grid 
cap) version of the 6K7.  Also, check that they didn't mess with the 
screen grid resistor value.

Have fun,
Al

On 10/22/2012 2:35 PM, Mike Sanders wrote:
> Greetings all, I am not a serious military collector or user but
> enjoy playing with and using some pieces of military gear in
> particular receivers.
> I have and have had several BC348s over the years.
> Currently I am looking at a friends 348 C from RCA. I am aware
> of the history of this model to some extent. I have generic paper
> work on BC348s that helps some. However this receiver has a
> couple mods and before I go to reverse engineer them I wanted
> to see if anyone has any info on them.
> The VT48 type 41 output tube has been replaced with a 6V6 and the
> 1st RF VT86 type 6K7 has been modified to a 6AC7. My primary goal is
> to get the radio working but getting it back to "stock" might be
> worthwhile as this appears to be a rather rare 348.
> It has an AC power supply in it and some cabinet holes. The cabinet
> appears to come from a P model. So this one will never be a museum
> piece.
> Any help on the mods would be much appreciated. 73
>
>
>
>
>                          Mike Sanders
>                               KØAZ
>
>
>
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-- 
Al Klase - N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/