[Milsurplus] BC-348 Audio tube bias

[WA5CAB at cs.com]

If your AC supply doesn't use the twist-tab aluminum can filter capacitors, 
I would pull the B- off of ground.  If it does, that might be a problem.  
As Hutch mentioned, the JNQ also derives fixed bias for the mixer from the 
B-, taken across two 50 ohm resistors in parallel, in series with the choke.

If anyone needs them, I have NOS audio packs for all models of BC-224 and 
all of the 348's EXCEPT the JNQ.  They aren't usable in the JNQ because the 
choke is grounded internally and you couldn't get the mixer bias.

In a message dated 01/17/2016 12:53:16 PM Central Standard Time, 
milsurplus at mailman.qth.net writes: 
> Almost finished sorting out and rewiring/removing old mods, etc.  I have 
> an AC supply in the radio, and the B- is grounded.  The VT-152 (6K6) 
> cathode would like to have a bit of negative bias to avoid distortion.  Read that 
> it should be around -18V some where, and the B- is also ungrounded and 
> connected to the VT-152 on the BC-348 schematics.  Should I just pull the B- 
> off of ground, or put a resistor in the cathode of the VT-152 (6K6)?
> 
> 
> thanks,
> 
> 
> John WD5ENU 
> 
> 

Robert & Susan Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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