FX Loop Not working suddenly

[OlBoyMikeRyan]

hey guys,

this has happened a few times before and resolved itself but I can't for the life of me remember how. The issue is that suddenly the FX loop doesn't work. I haven't had a functional footswitch for a while now, but when I switch the settings in the back (my Mark V is the 90w combo) for the loop assign to the "on all" setting, the volume cuts out by 1/10th. When it's set to specific channels, everything works as normal besides any FX in the loop, which do nothing at all. Thoughts?

 

[KRichter]

I had several issues with my MKV, ended up sending it to Mesa. They had replaced a few diodes, relays, but one thisg I noticed is that they replaced one of the jacks in the loop. I've heard from some others that shooting it with some contact cleaner did the trick. There is so much stuff packed into one of those it's really hard to say. That would be the first thing if you haven't done it already. Just a note, there is a huge volume difference when the loop is in the bypass mode. That's natural.

 

[Eevil]

hey guys,

this has happened a few times before and resolved itself but I can't for the life of me remember how. The issue is that suddenly the FX loop doesn't work. I haven't had a functional footswitch for a while now, but when I switch the settings in the back (my Mark V is the 90w combo) for the loop assign to the "on all" setting, the volume cuts out by 1/10th. When it's set to specific channels, everything works as normal besides any FX in the loop, which do nothing at all. Thoughts?

Most amps I’ve had with serial loop have had some intermittency as the connectors will accumulate some gunk in them.

My solution has been short jumper cable from send to return this has cured most non-tube related stuff with fx loops (with other brands also - not Mesa explicitly)