[R-390] SERIAL # 163

[Renée Deeter]

Hi Rich
I have a 390A from a Collins 51 contract, sn 122  with all early 
modules.  there were many mfgs of the rcvr....so who made it? also check 
the rear for matching sn/mfg as the tags were/are interchangeable.
go for the simple things first......I understand loosing just BFO 
output? or entire radio audio output?
if just BFO
1 B+ voltage on the BFO tube ( tube extender is good here)`if not how 
about dirty relay contacts..or are they actually switching?
2. check all voltages the tube if 5749(6ba6) should be about the same no 
matter the circuit....
3. is the tube good? try a couple by substitution as it could have a 
short internally
4. visual for burned parts resistance and cap checks.......
unless it is a mod it probably worked in the past...if it is a mod then 
the question becomes..did it ever work?
If all the audio.....hmmmm  short/open .... does the relay switch things 
other than B+? ie audio...remember back to simple first....lets not tear 
into it jsut to find the relay was ot switching and or making contact.
Renée, K6FSB

RICHARD MC KINNEY wrote:
> DE WB4VFN Rich
>   I have a R390a Serial @ 163.  Problem is turning on the BFO looses all output.  Rx is ok all bands with BFO off.  I have a manual for thr R390a but I guess mine is an earlier model.  The BFO in mine is nothing like the schematic.  Mine has a small relay that is switched on by the BFO switch.  I don't think this is any kind of mod as it looks factory wired.  The BFO circuit is also very different then the schematic I have.   The rig was given to me and I would love to see it work again properly.  So far I've had to change the 17 mc crystal and a few tubes to hear it work again.  Anyone have a schematic with a relay in the BFO switch?  73 Rich
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