Amp acting up...damping seems bad.

[SlyFoxx]

Having a bit of trouble with my ~13 year old Carvin X-100B. Seems like the amps damping factor is shot. It's not too bad when playing clean. (I always have the volume on 2 and it's a ~100 watt (EL34) amp so I never drive it too hard...plus I almost never use the dirt channel as I get my drive from a few TS9's and a Boss GT-6) The big trouble starts when I hit a really gained out patch like the 5150 model. I hit a big chord and mute quickly...but the speakers (1x12 carvin 100 watter and 1x12 celestion stolen from a marshall dsl 2000 combo...I think it handles about 75 watts) still ring out and make a nice burping or farting sound for a half a second before coming to rest. I don't think it's the tubes as I've has this amp for so long I usually know when to replace them. In additon to the problem on the clean channel I tested the drit channel and there is a bright fizzy (sounds like it's in the 5-6khz range)sound that wants to ride atop the notes and the damping seems messed up too.

Could this be signaling the end out my output tranny? I've taken contact cleaner to all the pots, jacks, sockets, etc...so it's clean as a whistle inside. I'll try new tubes soon but wanted to run this by you folks first.

-thanks-

 

[kmcguitars]

Re: Amp acting up...damping seems bad.

I'm thinking the Speakers maybe suspect? Could be some voice coil rub or cone cry? I assume the speaker you swiped from the Marshall had the matching Impedance with the Carvin?

 

[SlyFoxx]

Re: Amp acting up...damping seems bad.

No, speakers are not the problem as they work fine with my pro reverb. And yes they are both 16 ohms and DC resistance does read within 1/2 an ohm.

 

[Gearjoneser]

Re: Amp acting up...damping seems bad.

It sounds like the filter capacitors are nearing the end of their life. On a Marshall, they're the big blue cans. On the Carvin, they may be smaller, lower wattage ones, wired to the PC board. They usually last about 20 years, and that's how old the amp is.

This is a funny story, but when I was 17, I had an X100B. I hated the gain channel, but the clean was good, so I had it sitting next to a brand new Jubilee 2555. I was trying to sell the Carvin, but everytime someone came to take a look at it, it would start acting up. It always had intermittent problems. I got so enraged one day, I took the tubes out of it, and walked outside, spun the amp around while holding onto the power cord, and smashed it against a brick wall. My friends were standing there laughing while I smashed it into a dozen pieces. LOL

 

[SlyFoxx]

Re: Amp acting up...damping seems bad.

Filter caps...hummm. I'll have a look but I didn't notice any goo or odd stuff when I cleaned it. But that don't meanthey ain't shot either! But that's a pretty easy fix if it's the case.

Funny stroy here. Same pro reverb (1973) metioned above. It kept going out on me back...oh around the time I got the Carvin. I got so po'd one day I fliped the thing up in the air high enough for it to do a 720 and come smashing back down on the floor. Plugged it back in and it worked fine for a few weeks. Turns out it was just a loose rectifier socket. Got that fixed and it's worked like a pro ever since.

 

[Gearjoneser]

Re: Amp acting up...damping seems bad.

Since the amps have depreciated so much, AND it's starting to fail, maybe you should just go amp shopping for something new/used. It sounds like that amp served it's purpose for years, but if it cost $100 to fix it, it may by better to put that money into another rig.

 

[Robert S.]

Re: Amp acting up...damping seems bad.

Might be the filter caps but I'd check the tubes first. There is no way to know when a tube will start to fail until your amp sounds snotty. You might get 6 months, you might get a year or even two from a tube but then again you can get a bad tube straight out of the box.

Most of the time tube amps suffer from bad tubes but after 20 years it may be time for a cap job as well. My 1984 2203 is still getting by on the original caps but I'm sure the time will come when it will need to be worked.

Swap out the preamp tubes one at a time and see if you can isolate the problem. If not them get the amp benched. Tube amps are not a big mystery and I'm sure you can get it diagnosed fairly easily and cheaply.

Trannys can live forever unless you heat them up with a mismatch. That wouldn't be my first guess.

 

[SlyFoxx]

Re: Amp acting up...damping seems bad.

Thanks guys. Had practice tonight...and brought my pro along but the carvin worked fine. Arraragghhhh go figure. There's still a problem but....

Maybe I just need to let ALL the smoke out and be done with it!