Ampeg AM radio

[drewl]

Got an old Reverborocket 2, GS12R here and after getting it working right, the local AM station is getting picked up.
I just read the other thread there with the classic rock being amplified by the 18w, funny.
If you pull the input 12AX7 it goes away.
I reworked the input grounds, checked input grounds, I was going to rerun the sheilded input cable, and after looking at the schem I see it goes through the trem and tonestack before the volume pot, decreasing the volume lowers the AM, although it looks like it's present at V1's output.
I'll try grounding after v1's output cap.

Anything else to check?

[drewl]

Okay, grounding the output of V1 after the coupling cap kills this AM religeous station.
Ah, there it is, grounding cathode to chassis with jumper gets rid of the Bible studies.

[nickb]

You could add a smallish resistor in series to the grid of the first stage, around 68K, to attenuate RF. Locate it right on the grid pin.

[Jazz P Bass]

Are you saying that you reinforced the cathode resistor connection to ground or that you bypassed the resistor & connected the cathode directly to ground?
If the later, you turned the tube off didn't you?

[nickb]

...grounding cathode to chassis with jumper..

Not a good idea. The stage will be biased incorrectly.

Direct broadcasts from Christian Radio Stations are reputed to be very troublesome

[J M Fahey]

Add the resistor suggested by nickb on post #3 .
If not enough, add a 47pF or 100pF cap (as small as possible is better) from grid to cathode, straight at the tube socket.

[drewl]

No I didn't ground the tube's cathode.
Even though the cathode resistor's ground measured zero ohms to the chassis, grounding that ground to the chassis killed the radio signal, so I just added a jumper wire from the input jack ground to V1 cathode resistor ground.

Problem solved.