[Milsurplus] BC-620-F on Ten?

[WA5CAB at cs.com]

Roger, Dennis & Group,

Another challenge is that you can't fit enough 9-volt batteries into an empty 
BA-41 to duplicate it.  If the old 30-volt radio battery were still 
available, you could do it with three of those, but last time I tried, all I could 
locate were 22.5, 45, etc.  Next problem is that it's hard to find even dud 
BA-41's and the 5-pin socket in the top is smaller than a standard tube socket and 
I've never located a source.

Last BC-620 that I brought up I did a different way.  In the next ones, I'm 
going to try Dennis's circuit.  But one thing I wanted to mention is that 
9-volt batteries are convenient to use, readily available along with pig-tailed 
connectors for them.  For the -4.5 volt bias requirement, I first determined that 
the audio amp worked just as well with -6 volts.  So I took one 9-volt unit, 
opened the bottom and flipped over one of the cells, and closed it back up.  
Works fine as a negligable current 6-volt bias battery.  And fits better into 
the stack of other 9-volt batteries than any other available 4.5-volt battery 
would have.  Of course, I marked the battery and its connector 6V.  Still 
working fine in a Half-track in Kansas.

In a message dated 1/6/2005 4:23:37 PM Central Standard Time, W7QHO at aol.com 
writes: 
> However, the primary challenge encountered in operating either of these 
> sets 
> today is what to do about BA-41 which provided the 60- and 25-volt 
> potentials 
> required by the AFC circuit and -4.5v bias for the receiver audio amplifier. 
>  
> This special battery fit inside it's own box on the transmitter/receiver 
> chassis .   The -4.5v for the receiver is no problem, but the other voltages 
> would 
> require a considerable pile of currently available 9 and 1.5v cells to 
> replicate.   Not an impossible solution, but one ends up with the chassis 
> festooned 
> with made-up strings of batteries.   Works OK but rather untidy.
> 
> What we came up with instead is an FET circuit that replicates the function 
> of the original DC amplifier (triode part of V12).   Uses only a couple of 9 
> 
> volt batteries and a few other parts and hides neatly inside the original 
> BA-41 
> compartment. Can provide circuit details if you would like to give it a try.

Robert & Susan Downs - Houston
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