Mesa boogie Quad preamp Problems!

Hello boogie board pepples!

I recently bought a mesa boogie quad preamp. I got it just this morning, and the first thing I did was get it retubed. I got it home, and started playing through it. The first thing I noticed was that every channel and mode were on at once. I could not switch between channels or modes. Also, the eq rhythm/ eq lead switches have no effect. After playing for a little while, a fizzing noise started to appear. When I turn it on, it will either have all modes on at once, or I cant get any sound from it at all.

does anyone have any Idea what is wrong with it? if so, I would greatly appreciate your help.

How are you controlling the Quad? As I recall, you can activate everything at once if you're using a MIDI controller instead of the Mesa footswitch. However, it sounds like something is amiss in your Quad.

I dont even have the footswitch hooked up to it- I'll probobly have to take it back to the tech...

hi hessian,

There's a 7406 logic chip in the switching circuit of your quad. Judging by where it's located in the circuit, it's safe to say that it's the cause of your problem. It's most likely dead and needs replacing. As to what caused the chip to die, it could have happened by itself (it's not uncommon), or because a fault in the powersupply. The older Boogies use Zener diode voltage regulators in the supply, and when these diodes fail the full dc voltage is fed past them into other parts of the amp. Ouch. Find a good tech

All the best,

Jonny

edit - made it clearer

If you speak to Mike B. he will tell you that they can replace the whole switching circuit with one from a Mark IV for about 200$ including a new pedal board. This will make everything work. The old circuits had problems with impedance as well.