[R-390] Gain drift

[Larry H]

Hi Dave, This sounds like a tough one.  It could be most any contact: tube,
switch, or wiring socket.  RF deck switch would be my 1st choice.  Do you
have any subchassis you can switch out?  You might need to narrow it down.
And yes, it could certainly be one of those SILVER MICAs acting up.  You
might try some cold spray on them one at a time.  Since it happens on more
than one band, you can eliminate the 'band' section of the RF deck (but not
the switch or tube contacts), but it could be the 2 variable IFs.  If it
happens above 8mh, then it should not be the 1st var IF.

Good luck Dave.

Regards, Larry

On Sat, Oct 13, 2018 at 10:32 AM dog <agfa at hughes.net> wrote:

> I'll try some of these things, especially measuring the AGC when it
> happens. It takes a while because it's not always happening. I'm still
> not sure if it happens below 9MHz but I'm thinking it does. It's not
> just on one band and the BW on the IF appears irrelivant except for more
> or less noise out which is normal. This is one of those buggars to find,
> it takes so long to happen. I thought about cleaning the bandswitch but
> haven't gotten it out yet. I see the 2 green screws on the front of the
> 2nd Osc module to the RF module are missing. I'll replace them next time
> the front panel is off.
>
>
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