'61 Ampeg R12-R Hum

[ca7922303]

It's worth a try. I thought that with V2 removed and it still humming this would eliminate the footswitch but try disconnecting it anyway.

Actually with (V2) removed, reverb does not function, but tremelo does, so I guess I'll go ahead and remove footswitch wires from that terminal.

[ca7922303]

It's worth a try. I thought that with V2 removed and it still humming this would eliminate the footswitch but try disconnecting it anyway.

Disconnected footswitch wires from terminal, no change in hum. Is there a way to test the filter cap? Also here's a photo of paper capacitor that looks a little off maybe? The yellow Hy-Met cap.

[g1]

Grounding the PI (V4) grid kills the hum. To me that means the filter caps are all good and the hum is getting in through the PI stage.
That paper cap is wax covered and looks normal for that type of cap. Without knowing exactly where it goes in the circuit, it's impossible to say if it could be a factor.

Have you been able to identify the markings on the tubes yet? Try swapping the two 6SL7's around.

[ca7922303]

Grounding the PI (V4) grid kills the hum. To me that means the filter caps are all good and the hum is getting in through the PI stage.
That paper cap is wax covered and looks normal for that type of cap. Without knowing exactly where it goes in the circuit, it's impossible to say if it could be a factor.

Have you been able to identify the markings on the tubes yet? Try swapping the two 6SL7's around.

Yeah, markings are gone on all the preamp tubes but looking at images online of 6sl7/6sn7, that's probably what they are and I have swapped them all around and no change.

[ca7922303]

Grounding the PI (V4) grid kills the hum. To me that means the filter caps are all good and the hum is getting in through the PI stage.
That paper cap is wax covered and looks normal for that type of cap. Without knowing exactly where it goes in the circuit, it's impossible to say if it could be a factor.

Have you been able to identify the markings on the tubes yet? Try swapping the two 6SL7's around.

Looks like that mustard paper cap has a wire from the positive end running to (V3) pin 2.

[ca7922303]

Grounding the PI (V4) grid kills the hum. To me that means the filter caps are all good and the hum is getting in through the PI stage.
That paper cap is wax covered and looks normal for that type of cap. Without knowing exactly where it goes in the circuit, it's impossible to say if it could be a factor.

Have you been able to identify the markings on the tubes yet? Try swapping the two 6SL7's around.

Just installed 2 new 6v6s, 1 new 5y3, no change in hum and 6v6s now read V5(37mA), V6(45mA)

[g1]

Are they supposed to be a matched pair of 6V6 ?
Swap the bias probes around and make sure your higher reading (45mA) stays with the same socket, not with the bias probe.

[ca7922303]

Are they supposed to be a matched pair of 6V6 ?
Swap the bias probes around and make sure your higher reading (45mA) stays with the same socket, not with the bias probe.

They are both mesa matched to str 417/27 MP YEL but one is (37mA) and the other is (45mA) either socket installed

[g1]

They are both mesa matched to str 417/27 MP YEL but one is (37mA) and the other is (45mA) either socket installed

I'm wanting to check that your 2 bias probes both give the exact same reading for any one tube.

[ca7922303]

I'm wanting to check that your 2 bias probes both give the exact same reading for any one tube.

Only have one bias probe.

[g1]

Only have one bias probe.

Ok. Previously you had 6L6's that both read the same. Were they bought as a matched pair? These 6V6 are a bit out but I guess it's not the issue as with the matched 6L6 it still hums.
V2 pin5 connects to 2 caps, C18 and C19 on the schematic. Lift one end of each and see if it affects the hum.

[ca7922303]

Ok. Previously you had 6L6's that both read the same. Were they bought as a matched pair? These 6V6 are a bit out but I guess it's not the issue as with the matched 6L6 it still hums.
V2 pin5 connects to 2 caps, C18 and C19 on the schematic. Lift one end of each and see if it affects the hum.

C18 reduces the hum down to a level that probably would work for recording. C19 did not.

[g1]

C18 may be leaky then. Try a replacement. Also make sure the 470K (from one end of C18 to ground) is good.

[ca7922303]

C18 may be leaky then. Try a replacement. Also make sure the 470K (from one end of C18 to ground) is good.

I'm getting (0.5m ohms) from one end of C18 to ground.

[SoulFetish]

I'm getting (0.5m ohms) from one end of C18 to ground.

that's weird