evh 5150 mk III - gain completely vanished on channel 3 help!

[reneisgod]

I just bought a used EVH 5150, I literally played the 3rd channel for
5mins and all of a sudden the gain was gone completely.

When i turn the gain channel i get no boost of gain, the 2 other channels r fine and the vol works fine on both channels, i checked the tubes and they are all good, any ideas?

 

[EffigyForgotten]

Same thing happened to my blackstar stage 60 combo, the highest gain channel just completely stopped working yet the other channels worked fine. I sent it to a guitar tech got it fixed and after that the amp never sounded the same as before.

 

[Sloan]

Check cleanliness of tube pins, tube sockets, all 1/4" jacks, and all potentiometers.

 

[53Crëw]

Generally, when something like this happens it's a bad preamp tube. Are you sure they are all fine? If not a bad tube, then as Sloan said, dirty pin sockets, etc.

Maybe you already tried, but if you have a spare preamp tube swap them out one at a time and see if the problem goes away.

If not a bad tube or dirty contacts then my next guess would be a bad relay or something which you'd need a tech to isolate and fix.

 

[reneisgod]

ill try switching some of the tubes around i have 2 spare kicking about.

 

[Sloan]

I figured you had already switched around preamp tubes.

Remember that 12ax7's are actually two tubes in one package. You can have one side of a tube go out and still have the other functional.

 

[reneisgod]

Changed all the tubes, didn't make any difference.
Decided to give up for tonight so i put in the old tubes screwed on the grill left it for 10 mins then BANG! gain back on.
I gotta believe if its went out once its gonna happen again and its just being temperamental.

anymore idea based on the above? im just waiting for the gain to drop out on me again, anytime soon now lol

spoke to the guy that just sold me the amp, he has had not problems with the amp since day 1, possibly it took a knock during courier.

completely clueless now.

cheers

 

[reneisgod]

AGH just went on to the blue channel and back to the red and the gain has yet again gone!

 

[Firaxis]

If it's intermittent then it might be a bad connection in the tube socket, maybe a the contacts aren't a tight enough fit

 

[metalfanat1c]

If this forum is anything to go by, these amps are unbelievably unreliable...

 

[reneisgod]

sorted!

i removed the chassis and sprayed the Gain pot with contact cleaner,
reassembled and the problem was gone!

 

[Sloan]

great!