[R-390] R-390A BFO Stability

[Larry H]

Renee, Thanks for the reminder to check the components, first.  Replaced
the tube and measured the resistors and no significant change occurred.
Measured the capacitors and no problem found there.  Sub'd my good spare
BFO and is much improved, so opened up the original BFO and found that the
2 - 50 pf caps had been replaced before.  One had no markings on it and the
other was 50pf N470.  I replaced the 2 with one 100 pf N750, and now it's
quite good.  At 1 minute after power on I set it at 455kc -10 cycles and in
10 minutes it's at +5 and hangs around there +/- 2 cycles for 50 minutes,
then drops down 3 cycles and stays there for an hour +/- 1 cycle.  That's
good for one of these units.

Regards, Larry

On Fri, Aug 16, 2019 at 10:52 PM Renee K6FSB <k6fsb.1 at gmail.com> wrote:

> Larry- you might check a couple of resistors in the circuit...I had some
> that were heat sensitive in an osc circuit long time ago was not this low a
> f as this...of course the caps are the obvious suspects even the postage
> stamp ones!, you may have to open the mini-pto.......
> keep us posted
> Renée, K6FSB
>
>