MKIV Switching Matrix: Vactrol Hades!

[fdesalvo]

Hi, all.

This chump is stumped. 5/12v power supplies are healthy, but I'm experiencing an issue detailed here:

I have a MKIV (G revision?) on the bench currently that is not allowing rhy1/2 to work independently. Whenever R1 is selected either by FS or the rear panel, both R1 and R2 LED's illuminate. When R2 is selected, R2's LED illuminates and R1's glows faintly. I can't locate any schematics around this circuit and the board states "MKIV-G" as revision. Any help is appreciated. This is Vactrol hades!

 

[Blueracer]

Hi Frank. I have attached schematics for both the A and B Mark IV versions. Hope they help. A long time ago in a galaxy far far away I did help another member sort out his Mark IV switching issues. If you would like assistance with your problem I may be able to help. As a start I would disconnect any external foot pedals that control the amps mode and see if the mode switch in the back is functioning properly.