[ARC5] BC-342's

[WA5CAB at cs.com]

Maybe.  If no one has already changed them, there are jumpers on the 
terminal strip that the DM-21 or RA-20 attaches to that will differentiate a 
BC-312 or a BC-342.  Any letter model.  If the terminal strip still has MFP on 
the solder terminals, it's probably the original wiring.  If it doesn't, then 
it probably isn't.

One other differentiation is that if there is a wire running to the ring 
terminal on the SPKR 2nd Audio jack from the +12 VDC line, it's a 312 model 
earlier than N or NX.  If there is no wire, it's either a 342 or a BC-312-N or 
-NX.  This wire was a carry-over from the original BC-312 (no suffix 
letter).  It supplied bias to the field coil in the prececessor to the permanent 
magnet LS-3 and was a carry-over from the BC-189,-A.

If the audio output transformer has a 250 ohm tap on the output winding, 
it's an M or an N.  RCA built the M and Farnsworth the much more prolific N.  
In the M, you had to make a solder connection change to switch the output Z 
from HI to LO.  In the N, there was a two-terminal terminal strip and a male 
pin plug to do the change.

If the tube filaments were originally wired for 24 volts, it's a BC-312-HX 
or -NX.

There are some other specifics that will help identify early model 312 and 
342 and some late model 312.  See TM 11-850 1946 edition for the chart.

In a message dated 09/21/2012 21:10:38 PM Central Daylight Time, 
releazer at earthlink.net writes: 
> Anyone know of any way to tell the difference between a RCA made BC-342 
> and a Farnsworth one?
> 
> I have a BC-312/342 ( do not know which) that has no name tag and I am 
> curious about the differences between to two mfrs.  I guess that it is 
> probably a BC-312 given that an external homemade power supply was used.  I am 
> going to install a DM-21, of which I have acquired 3.
> 
> I plan to fabricate a new name tag using a photo of one, some image 
> manipulation, and photo quality printing. 
> 
> Thanks
> 
> Wayne
> ___________

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