JP-2C problems?

[VictimsOfDeception]

Recently, I've noticed a major change in the tone of my Mesa JP-2C. There's this extremely unpleasant fuzz that is especially noticeable on the neck pickup when I do lead stuff, but it's also there somewhat when I use the bridge pickup for rhythms as well. I'm using the exact same settings as I've been running the last few months, but the change is drastic. Additionally, on the clean channel, if I sustain a note high on the neck, again using the neck pickup, I can sometimes faintly hear one of the dirty channels coming through the speaker, but it's much less noticeable than the other problem. Really not sure what the culprit could be, as I'm pretty inexperienced when it comes to amp maintenance.

Anyone know what could be going on?

 

[Nicki]

Could be any number of things.

I'd turn it on and have a look at the preamp tubes. They rarely go bad but that doesn't mean that they can't. If they're all glowing evenly then the tubes are probably fine. Take a look at the power amp tubes for the same thing. Those go bad more often. If, visually, you cannot see anything obvious, take it to an amp tech.

 

[efiltsohg]

glow has very little to do with functionality of tubes, swap them 1 by 1 with a known good spare

 

[Seamus McFlanery]

It could be the cab clone. That was giving me problems on mine. Otherwise, I'd say maybe there's something wrong internally, like a cap or solder issue.

 

[Vince]

99.9% of the time this is caused by a preamp tube. Snag one or two 12ax7 tubes and swap out each tube one by one until you find the problem tube. You own a tube amp now, this is basic maintenance you will need to do from time to time.

 

[Emperoff]

Try checking preamp tubes as mentioned, and if that doesn't solve the problem take it to a tech.

 

[cardinal]

These things are so complex that it's hard to trouble shoot. I had a Mark III acting up and folks were trying to help me and I just couldn't figure it out and had to send it back to Mesa. At least in my case it seemed to be a bunch of things wrong at once.

 

[c7spheres]

Check the fuses. I've many times had a fuse only partly blow and the tone goes to crap like you describe and it will sometimes be ok then go back to crap. Everything gets thin and spongy and brittle. Half blown fuses still let everything operate normally but are kind of intermittant. Maybe it's that. This is especially true if you have a slow blow fuse where a fast blow fuse should be.