Crate GLX65 Channel Switch Issue

[misterc57]

I have a GLX65 that is stuck on the clean channel.

Pressing the front panel "SOLO-RHYTHM/CLEAN SELECT" button causes the channel LED lights to switch over to the correct channel but the CLEAN channel remains the active channel regardless of switch setting.

Other notes;

Pressing the "SOLO/RHYTHM SELECT" button causes the LED light to switch between SOLO and RHYTHM.

The CLEAN channel LED light is never ON.

Any ideas on this issue?

Thank you

[misterc57]

Attaching schematic

[Enzo]

Page 2 of drawing, lower left. That is your switching circuit. See all those six-sided circles around letters like A or B? Those are the control signals going to the audio places. Page 1, top half, This is the signal circuitry. See all the JFETs with their gates tied to one letter or another: A, B, C, etc. Those are the switching elements. They do things like pass signal through or shunt it to ground. Or they change the gain in a stage. That sort of thing. If one of those shorts, then it is stuck in whatever setting that represents. Or if the control signal is stuck, then the JFET cannot change states. You need to explore that stuff.

[g1]

There is a table showing which voltages should appear at those A,B,C points Enzo mentioned. It's on page 2, sector F-3 labelled 'switching logic'.

Also, if you do not have a footswitch connected, the footswitch switching jacks (on amp rear panel) need to make connections and may need cleaning. Schematic attached shows pins 1&2 need to connect, as do pins 3&4.

[misterc57]

The way the pre-amp board is situated this is a tough (for me) board to debug. I have not been able to view the top side of the board when testing. I probably should try to float that board with the components facing up as I continue.

I re-flowed half the "SOLO/RHYTHM SELECT" button pins which looked questionable. I cleaned the foot switch jack in the back. Cleaned all the pots.

Now, more is working. The SOLO channel is working but the RHYTHM channel is very faint to hear. Clean channel still works fine.

[Enzo]

Here is the board layout