Mark IV stock footswitch Ld and Ld-EQ switches not work

[Nlynch1]

Everything was wonderful with my amp but after moving it one day, the footswitch Lead and Lead/EQ buttons no longer work.

When i press Lead switch (when currently on R2) it switches to R1.
When i press Ld-EQ switch (when currently on R1) it switches to R2.

Everything works when i switch channels using the manual switch on the back of the amp.
Also, the individual footswitch jacks work fine.

Any ideas what could be wrong?

I tested all of the wires from the pedal board to the plug on the amp side. They all register <1ohm only along each wire, so there isn't a short somewhere in the wire.

 

[vhyken]

i've experienced this with my mark iv-a.. same problem.. just brought my amp to my local amp tech and he just cleaned the switching matrix.. he did remove it and scrape maybe dust from the contacts?.. then boom! back to normal

 

[Sp3ktral]

check the ICs in the FS and Head to make sure they are getting power and functioning correctly.

 

[Blueracer]

Basically the problem you are having is pin 1 of the XLR connector (the connector to the footswitch) is stuck in a logic low condition. The problem can be in either the amp or the footswitch. It is easier to start with the amp. To check if there is an issue in the head do the following. Disconnect the footswitch but leave the selector switch on the back of the amp in the footswitch position (this is important). Power up the amp and the lead and eq LEDs on the amp should light up. I am assumining both of these LEDs worked before you had a problem. Try this and post your results.