Triple Rectifier ground hum issue

[DS-1]

Hi guys!

It's a couple of weeks that my Triple Recto sometimes has this ground hum coming out from the speaker. The guitar doesn't sound at all or sound like a broken jack when the hum comes out.

It happens always when I was on the clean channel. Switching from a channel to another one seems to solve the issue.

The ground hum doesn't show every time I use the head and this is annoying because I can't consider my head usable for a live, now.

Anyone has this issue before?

Thanks in advance for the help!

 

[domct203]

Are you using the FX loop when this happens?

Have you tried Hard-Bypassing the FX Loop to see if anything changes?

 

[DS-1]

Are you using the FX loop when this happens?

Have you tried Hard-Bypassing the FX Loop to see if anything changes?

No, I'm not using the FX loop. There's nothing between SEND and RETURN.

 

[domct203]

If the FX loop is not Hard Bypassed, it’s tube buffer is still in the circuit regardless.

When this happens again, flip the FX Loop to Hard Bypass and see if anything changes. If not, you’ve eliminated one of the preamp tubes and the FX Loop circuit as a source of the issue. If the amp roars to life, you’ve narrowed it down a bit.

This could also be in the muting circuit, does it always happen only on channel 1, and every time you’re in ch 1?

 

[DS-1]

If the FX loop is not Hard Bypassed, it’s tube buffer is still in the circuit regardless.

When this happens again, flip the FX Loop to Hard Bypass and see if anything changes. If not, you’ve eliminated one of the preamp tubes and the FX Loop circuit as a source of the issue. If the amp roars to life, you’ve narrowed it down a bit.

This could also be in the muting circuit, does it always happen only on channel 1, and every time you’re in ch 1?

It happened three times, when I was on ch 1. Today I used ch 2 only and I had no issue at all.

It could be something related to the muting circuit, because a couple of years ago I had the "mute issue" (no led channels on the front and no sound at all) and the technician that fixed my Mesa told me it was a muting circuit relating issue.

 

[DS-1]

An update:

I turned on the amp and switched to ch 2. Played it for half an hour without issues.

Then I switched to ch 1 and, after a couple of minutes, the ground hum started. So I played with the ch1 volume knob and the hum disappeared when I turn volume up, but the issue wasn't finally solved. After another 10 minutes of ch1 without playing, the hum disappeared.

While the hum was present, I switched to ch2, played a couple of minutes without issues, then switched to ch1 and the hum started again, so I believe it's something related to ch1 only, maybe any preamp tube?

 

[domct203]

Is this a 2 channel or 3 channel amp?

The 3 channel version has one triode of V1 used exclusively for channel one. If that specific triode should fail only channel one would be affected as you are experiencing and you could try changing V1.

The earlier 2 channel amps did not do that, both channels used the same tubes for both channels, with one triode of V1 unused. The issue you describe would be more likely found in the mute circuit or LDR switching components.

 

[DS-1]

Is this a 2 channel or 3 channel amp?

The 3 channel version has one triode of V1 used exclusively for channel one. If that specific triode should fail only channel one would be affected as you are experiencing and you could try changing V1.

The earlier 2 channel amps did not do that, both channels used the same tubes for both channels, with one triode of V1 unused. The issue you describe would be more likely found in the mute circuit or LDR switching components.

Mine is a 2000 3ch Triple Rectifier. In these days I'll try with a different V1 tube.