[R-390] bfo problems

[ronald j deeter]

I had a very similar problem tracked it down to a filament to cathode
short on the AGC rect tube V509. 
So look for a tube.
substitution is the fastest way to track it down.
Ron
R390A Collins S#122 contract 375-P-54

On Thu, 02 Jan 2003 18:52:35 -0500 "Steve Hobensack"
<stevehobensack@hotmail.com> writes:
> My r-390a has a slight hum when the bfo is on. Cw and ssb signals 
> have a 
> slight "vibrato" sound. Cw notes are not clean and crisp with any 
> setting of 
> the mgc level. I suspected one of the filter caps, but they are ok. 
> The 
> decoupling cap on the bfo 150v b+ is ok , there is no cathode to 
> filiment 
> short. I turned off the bfo switch, and injected a 455 khz carrier 
> from my 
> urm-26d signal generator to pin 5 (plate)of the tube socket. I still 
> had the 
> hum with the signal generator acting as the bfo. The radio sounds 
> fine 
> listening to a m broadcast. Any ideas ???  Thanks
> .......Steve.....KJ8L
> 
>

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