Boogie Mark IV B with bad optocoupler on lead channel help!

[g1]

I looked thru my Mesa Folder to see if I have more schematics on the Mark IV. Not all of the schematics are present. It's missing the Switching Matrix, where all of the LDR's are shown being switched from the transistors being turned on to turn the LDR's LED's on, doing the switching. And, it's also missing the power supply schematic.

Is it different from the B ?

[Pedro Vecino]

Mark IV. Power supplies and switching matrix 1/2.

[ATTACH=CONFIG]58531[/ATTACH][ATTACH=CONFIG]58533[/ATTACH][ATTACH=CONFIG]58534[/ATTACH]

[nevetslab]

Mark IV. Power supplies and switching matrix 1/2.

[ATTACH=CONFIG]58531[/ATTACH][ATTACH=CONFIG]58533[/ATTACH][ATTACH=CONFIG]58534[/ATTACH]

Thanks, Pedro!

[nevetslab]

Is it different from the B ?

This folder is from the one I have. Mine didn't have the Block Diagram, nor the power supply, the two Matrix Switching diagrams nor the Foot Pedal diagram. Thanks.

[aiyiadam]

Any new information on this topic?

There is a Mark IV on my bench with the same problem.. Possibly a short circuit somewhere.. I will start from the LED (possibly disconnect it), go backwards on the lead rail and try to find the reason..

Somebody did something in this area. The EQ vactrol is damaged a bit..