Marshall AVT150H in need of some help!

[Benseven]

I own an AVT150 and recently someone spilled soda into the top vent of the head. Naturally the amp stopped working. So far I've cleaned up all of the boards perfectly with no result. I checked the fuses and they are all intact and the tube is working fine. When I turn it on I get power but no sound is produced with I try to play through it. There is a little bit of buzzing but that's about it. I took it to a local repair man and he was pretty stumped, telling me that it might be fixed by switching out the motherboard. ANY advice would be much appreciated!!

[Enzo]

Switching out the board? Yes, buying a new amp usually takes care of a problem.

Get systematic. Are all the power supply rails intact? The power amps run on I forget what +/-35v maybe? And the op amps run on +/-15v. Are all four of those present?

COnnect the FX send to another amp for a listen. ANy signal coming out there? Likewise, plug your guitar into the FX return jack. DOes THAT come out the speaker?

Is signal getting to the input pin of the power amp module? Is power getting to the modules? The three pin connector on each power amp module carries its power.

On the schematic, look on the power supply page. Bottom center is a small circuit making the standby signal - STBY. That is done by T104, ZD100, and C217. If any of those are shorted the amops stay in mute.