[R-390] Gain drift

[Larry H]

Dave, good deal on getting your 2kc filter working and installed.

When you said that the level  jumped 10db, did you mean on the carrrier
level meter?  If yes, then the 4th IF does not normally affect that reading.

The 'snap' when touching the mV meter probe on the plate is interesting, do
you normally get that?  Not sure why that would cause it to temporarily
work.  Do you have vtvm dc readings for the plate, screen, CG, and cathode,
when it's not working?

About the IF's that need stagger tuning, I believe they were only used for
the 1st couple years and did not have the Q reducing resistors in them.

Regards, Larry

On Sat, Oct 27, 2018 at 8:55 AM dog <agfa at hughes.net> wrote:

> It's not over yet. I just turned on the rx after being off overnight and
> fed 150uV into the IF section, and after a few minutes got -1.5V on the
> diode load, measured the RF on grid and plate of V504 and it seemed
> pretty low. I touched the plate with the mV meter, there's a snap and
> the gain jumps up about 10dB and the DL goes to -7V, where I'd set it
> last night. Then right away it starts drifting back down to where it was
> while I had the mVmeter on the plate, I watched it go down. Still
> something not right in that circuit. I did take off the cans to the
> other two IF interstage transformers and they look normal with the
> proper resistors and caps.
>
> How does one know if a rx is supposed to be stagger tuned or not in the
> IF strip. Apparently there are 2 kinds. I tried stagger tuning T501 and
> T502, but it seems like 467 and 448KC is barely available at the DL
> where 455 is. I need to get the 2KC filter in my other IF module fixed
> and put that one back together. I may work on that today.
>
> Dave N3DT
>
>
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