# Jet City amp troubleshooting?



## Tyler Greig (Mar 2, 2013)

I don't have a lot of experience with the inner workings of tube amps, so hopefully somebody here can shed some light for me...

I bought a Double Muff pedal (basically a Muff with 2 gain stages) used at Long and McQuade because it seemed like a good deal, came home and plugged it into my Jet City JCA20 head. It was sounding real good, until I flicked the pedal into "double Muff" mode. I may have had the gain on my amp too high at the time, but all sound from my amp immediately stopped as soon as I flicked the switch. Now, if I completely crank the volume and gain on the amp, I get barely a whisper of my signal to come through the speakers. 

It happened as soon as I engaged the 2nd mode on the pedal, so I know that was the culprit, and I know the problem lies in my amp as I've tested different guitars and cables that are known to not have any problems. I emailed EHX and they told me that the only possiblility was that I might have blown a tube IF the gain on the amp was up too high when the pedal was engaged.

I've since switched out the preamp tubes to no avail. Does it sound like it could be a power tube problem to anyone? Or am I going to have to take my amp in to a tech for some costly repairs? Any help will be appreciated, thanks.


----------



## surlybastard (Feb 20, 2011)

I don't know if I've ever heard of a tube amp blowing a power tube because of too much gain coming through the input, but I suppose it's possible. Someone else will have better advice than I, but my next move would be to change the power tubes to see if that would fix the problem.


----------



## washburned (Oct 13, 2006)

Did the same thing on my Koch Studiotone. Took a long time to find the problem, but it was finally tracked to all the SS stuff in the OD section. After a couple of op amps and new tubes I sold it and got an old fashioned point to point no SS stuff amp. Hasn't let me down.


----------



## Wild Bill (May 3, 2006)

I agree about solid state stuff. Anything solid state like an IC or transistor blows so fast that it is pointless to try to protect them with fuses. Fuses are just too slow.

Have you tried another speaker? I had an amp in my shop with the symptoms you described and it turned out the voice coil had opened up. I was surprised, 'cuz voice coils are just a bit of wire and you would expect they would need a little bit of time to get hot enough to burn out but with many modern speakers it seems the connections with that super flexible wire from the terminals to the speaker cone are not always that robust. Sometimes reheating the solder at the terminal will fix things.

Wild Bill/Busen Amps


----------

