[FrankieKat]

Well, I replaced the 15M resistor (R20) and made no difference -- the picture still has that noise and AGC control has no effect. I've checked and replaced all resistors and capacitors between the 1st IF grid, through the AGC control and to the plate of the AGC keying tube. I bypassed the AGC control with a low fixed value resistor and nothing different.

The DC voltages on the AGC tube and IF tubes are close enough to spec. Also verified all of the scope traces drawn on the Sams and frequencies are all correct, though P-P voltages vary a bit from the schematic but are within the right ballpark.

I don't see any visible HV arcing, and while there's an audible "pulse" that occurs with the noise, it sounds softer, more like a hold/sync issue than a sharper HV noise.

I swapped out every tube in the set last night including the HV rectifier and still no change. I can try to order up some more tubes to try (though I have at this point at least three of every one) if it's still possible it might be tube-related.

I injected an IF video signal from the VA62 after the third IF tube (with it removed) and still has noise and no AGC control.

I also saw no visible AGC control on the first power up of the set too, so I'm pretty confident that it's not related to something I did.

The only thing I've noticed is that the noise seems to go away when it's tuned a bit away from the station or the signal level from the VA62 is low.

Where could I be looking next?

Thanks!

FK

(schematic attached)