Carvin SX300 odd switching problem

[guitardad]

Sx300 with FS44 footswitch is improperly switching, and it's kind of random. From the panel (no fsw) it seems fine.

Connect the FS44 and it may switch ch 1 and 3, miss ch 2, and not properly show the channel selected when FX is switched on or off... i.e. the channel may be set to Ch3 but FX button on fsw randomly controls switch to channel 1 ir ch 2.

Flow through different channels and it changes again. Carvin is no longer serving tech calls for amps.

My thought is something on the DSP board perhaps U5, but the schematic is not laid out well. Numbering of connectors and such are not what are on the boards.

Works fine without FS44 other than the presence switch which when active on Ch3 is really noisy (with or W/o Fsw).

here's manuals for reference. Model is Sx300; boards are all REV E

https://carvinaudio.com/pages/guitar-amp-schematics

Thx in advance

[guitardad]

Ahhh poo! Can a mod move this thread to "Guitar Amps repair and Troubleshooting? Thanks

[g1]

Are you confident it is not the footswitch? Was the footswitch working before? Any chance someone changed some of the switches to the wrong type, like momentary instead of latching, or vice-versa?

[guitardad]

Are you confident it is not the footswitch? Was the footswitch working before? Any chance someone changed some of the switches to the wrong type, like momentary instead of latching, or vice-versa?

Yes. I had another FS44 I verified did the same thing with the amp.