Mesa Boogie Lone Star Hum Please Help

[Mars Amp Repair]

Yeah,
JJ power tubes have just gone to the crapper since a few years ago. I won't even use them unless a customer insists...then I put them in my tube burner & let them cook for 24hrs.
It looks like CE dist is offering 6L6 JJ's that have been burned for 24hrs now. I've had issues with both the 6L6's & the EL34 JJ's. glen

[Prairie Dawg]

Yeah,
JJ power tubes have just gone to the crapper since a few years ago. I won't even use them unless a customer insists...then I put them in my tube burner & let them cook for 24hrs.
It looks like CE dist is offering 6L6 JJ's that have been burned for 24hrs now. I've had issues with both the 6L6's & the EL34 JJ's. glen

Really. This is two, in two different Mesa amps, in two weeks, and a few blown screen resistors.

As Joe Leaphorn the fictional Navajo detective says "If you believe in coincidence you're not looking close enough." Plus, the guide pins on the octal bases are extremely fragile as well-easy to break.

I've got a set of JJ EL84s in my own personal, strictly for fun Vox and they seem to be fine. But I'm drawing the line there.

[Zouto]

Yeah,
JJ power tubes have just gone to the crapper since a few years ago. I won't even use them unless a customer insists...then I put them in my tube burner & let them cook for 24hrs.
It looks like CE dist is offering 6L6 JJ's that have been burned for 24hrs now. I've had issues with both the 6L6's & the EL34 JJ's. glen

Yeah, I had similar troubles with JJ 6L6s and EL34s. The heaviest case were getters becoming completely loose in 3 JJ 6L6s during normal operation in different amps like SF Twin Reverb etc. causing damage to the amps.I never use any of the JJ stuff since. Hardly had issues like that with any other brand.
Zouto

[zitek]

Hi, I solved this problem in my amp. But the cause was very simple.Through years of use, the aluminum chassis started to oxidize and in effect one of the ground pins lost its proper contact with chassis. Sand paper fixed it in a minute. I replaced this burnt resistors with old soviet ones and the amp works great.

[nedocaster]

Did you solve this problem?

Hi

Anybody solved this problem as final anode described? Seems to be simple mod but I am not sure wether I am thinking right or not.Is this hum a factory construction issue ? This is my lonestar inside:
http://zitek.republika.pl/lonestar.jpg

My lonestar looked just like this recently. I was changing tubes and didn't realize that one of them was missing the keyway, so it was installed incorectly. When I switched the amp from standby to on, it flashed smoked pretty bad.

[Tampi]

Lone Star hum fix

Hi

I have a hum in my Lone Star and the only fix I can find is yours. I'm having trouble understanding it, though. I was wondering if you could advise?

What you've said seems to make perfect sense given what everyone else has found, but which is the pot that you're referring to that has the earth connection on it? The only pot in the NFB circuit is the slave pot, which isn't earthed directly. Would you be able to be more specific?

The only pot that seems to have a separate connection is the Channel 1 gain pot, but I isolated this connection and it didn't change anything.

Regards, Mike

I have had this problem & have just completed the repair, the cause is an earth loop effecting the phase invertor, unsolder the earth wire from the pot, (the other end of the resistor goes to the 100 ohm resistor in the neg feedback loop), solder a solder tag, to the wire, then attach the solder tag to 1 of the power transformer mounting bolts, take off the other nuts on the power transformer & clean the aluminium chassis, ALL the hum had gone after this had been done.

Final anode