Mark 3 cutting out!

[Boogiemark3]

I had posted a while back about the amp sounding weak and buzzy but a tube change was all that it needed. Well, the other day I go to play on it and the sound was barely audible and there was a lot of hiss coming from the amp on all the channels. I started messing with the amp and I found that if I put the last slider on the EQ below the half mark i would get the volume back. I think that the slider is worn out and it is shorting the EQ section out when set above the half way mark. What should I do? I have been contemplating fixing it myself since I am pretty handy with a soldering iron, but I wouldn't know where to start.
Should I send it in to a tech, try to fix it myself, or send it to mesa?
I also was wanting send it in to mesa to have the IIIc+ mod done to it. How much that would cost with the repairs on top of that?

 

[acorkos]

how is your volume level when you manually switch the EQ off?

 

[Boogiemark3]

When the EQ section is turned off it works fine. Which leads me to believe the 80 slider is shorting the EQ out. The weird thing is now there is this loud hum on all the channels that wasn't there before.

 

[acorkos]

hum with the EQ switched off? you might have another problem besides the EQ.

I recently serviced the EQ on my MkIIB. the front panel needs to come off (so all the front panel knobs, pot nuts and switches need to be removed) in order to get the EQ board off the chassis.

Each EQ band consists of a slider pot, a resistor, a capacitor and an inductor. Any one of those could be causing your EQ problem. you probably need to pull each part off the baord and check for a short.