Weird thing with LSC gain channel

[jazzwannabe]

On my LSC 1x12 drive channel, the signal cuts out when I have the drive up past 2 o'clock. It sounds like the signal gets cut in half, and the bottom end disappears. If I whap the top of the amp, like you would with an old TV with a bad picture, the full sound comes back. But the instant I hit another chord or note, it happens again. This doesn't happen if the drive is set lower than 2 o'clock.

When I got this amp, the dirt channel would crackle and sputter for a few minutes before settling in and working right. It doesn't do that anymore, just the above-mentioned cutting out. I have plenty of known-good tubes on hand and have gone through all the tube-swapping in the front end and power section (but not the rectifier tube — I go back and forth between the silicon diodes and tube setting, and it doesn't seem to have an effect on the problem).

Any ideas? This amp is still under warranty, but I don't want to ship it to Mesa if I can help it.

 

[Monsta-Tone]

It sounds like a trip to the doctor to me. Is there anybody in your area?

I lived in Bakersfield about 18 years ago and don't remember any Mesa dealers in the area, but that was a long time ago.


Try swapping out only the tubes associated with the Drive channel. I know you have done this, but I just found a bad (brand new TAD 12AX7) preamp tube in V4 of my DC-3. I couldn't figure out why my amp was ticking and crackling on both channels. V4 is only for the Clean channel, but I could still hear the noise on the Lead channel.


My point is, that just because a tube is good, does not mean that your amp likes it. The TAD is bad, but it was a 'Known good tube,' to me before I discovered it was bad.



If this does not work, maybe you can find a good Mesa tech close to you.

 

[Barry]

On my LSC 1x12 drive channel, the signal cuts out when I have the drive up past 2 o'clock. It sounds like the signal gets cut in half, and the bottom end disappears. If I whap the top of the amp, like you would with an old TV with a bad picture, the full sound comes back. But the instant I hit another chord or note, it happens again. This doesn't happen if the drive is set lower than 2 o'clock.

When I got this amp, the dirt channel would crackle and sputter for a few minutes before settling in and working right. It doesn't do that anymore, just the above-mentioned cutting out. I have plenty of known-good tubes on hand and have gone through all the tube-swapping in the front end and power section (but not the rectifier tube — I go back and forth between the silicon diodes and tube setting, and it doesn't seem to have an effect on the problem).

Any ideas? This amp is still under warranty, but I don't want to ship it to Mesa if I can help it.

I would send it back to Mesa .For me , I would rather have the guys working on it that actually build the stuff . At least call them and trouble shoot it over the phone .

 

[jazzwannabe]

It sounds like a trip to the doctor to me. Is there anybody in your area?

I lived in Bakersfield about 18 years ago and don't remember any Mesa dealers in the area, but that was a long time ago.

I have a friend here who knows a guy who designed some of the 65 Amps or something like that, and he says the dude is like a NASA engineer. But if I do that, it's gonna cost me, and of course it will void my warranty (even though I don't want to actually use the warranty because shipping is a pain).

On the other hand, some techs won't touch a Mesa. Think I'll just get a new batch of preamp tubes and go through the process again.