Mesa Titan V-12 / Help with hybrid amps

[AEA]

Hey,

I have a problem with a Mesa Titan V12 bass amp. It seems to bypass the master volume for some reason intermittently. It is a big boost and I am not sure what could be the cause.

Now I have some experience with tube amps and I know how to safely service/modify them. I just wanted to get some advice on servicing hybrid amps and doing it safely and discharging any residual power that may be stored.

I know some people will say just take it to someone else but we all have to learn don't we? If I am totally stumped after poking around a bit then I will take it to someone else but if its just a cold solder joint or a wire that has come off or something small it will save the exorbitant price some repair guys are charging these days.

Also if anyone has any ideas why it would be bypassing the MV i would greatly appreciate it.

Cheers

[teemuk]

A quick guess: You have an intermittent connection in the ground return of that potentiometer. If the potentiometers are PC board-mounted you have just one solder connection to check, if they are connected to board with flyby wires then you have two.

Now I have some experience with tube amps and I know how to safely service/modify them. I just wanted to get some advice on servicing hybrid amps and doing it safely and discharging any residual power that may be stored.

Basically, you do it about the same way. The only difference is that instead of one B+ rail, from a hybrid you may find a B+ rail and two other power supply rails, one with positive and one with negative voltage potential. In a high power bass amp these rails may have fairly high voltage potential too. More than 100V across them isn't even uncommon.

The main filter capacitors should reveal the configuration after a bit of examination. Measure the voltage potentials with a VM and if they don't bleed out when power is disconnected then drain them manually with a resistor, just like in tube amps.