Mesa Solo Head 100 Dual Rectifier - No Sound

[earache]

Hello

I'm looking at a Mesa Solo Head 100 Dual Rectifier that makes no sound at all. It's history is that it has previously had a carbon track form between pins 2 and 3 of one of the power tubes. It has ceramic sockets and so I was able to completely clean all the carbon off and get it working again and returned it to the owner.
He later told me that it didn't work at all when he tried it but it had when it left me...

Anyway I have tried replacing all of the tubes with known good ones and no change. All of the tubes light.

None of the channel indicator lights on the front panel light up at all.

Nothing inside looks burnt.

Any ideas?

[Dave H]

Mesa_Boogie_Dual_Rectifier_Solo_Schematics.pdf

[drewl]

If the channel lights are dead check the low voltage power supply.

They use the heater supply as a source for the DC filament voltage and low voltage supply.

Usually the four 1N4007 diodes that turn the ac filament voltage to dc go bad.

[earache]

Drewl - thanks for the prompt reply, will check out those diodes

[earache]

Dave H - thanks for the great schematic - much appreciated!

[earache]

Drewl

You were completely right about the diodes. I could even see that the board had become slightly darkened around them. Replaced all four diodes and aall works great again.

Boy these Mesas are an ordeal to work on. Never like when I get a Mesa to fix...

Thanks so much for the great info and help!

Eric

[drewl]

Yeah, I'm seeing it alot on these amps that are ten, twenty years old now.

Any discoloration on the board under them and I replace them, keeping them higher up off the PC board.