fender twin amp volume surge in effects loop

[nickedm]

Hi there, I just bought a 2nd hand 90s Fender Twin Amp (no tremolo). When I plug my Line 6 POD XT Live through the effects loop floor I get a volume surge every 20-30 seconds. Don't get it when I run the POD through a PA so assume it's the Fender Twin. I don't get this problem when I plug it into the front of the Fender. I've also had a problem with switching between the high gain channel and the clean channel - sometimes it seems to get stuck and flicker between the channels. I got a 3 month warranty when I bought it from GAK - but before I go back to them I wanted to try and get a better idea of what might be going on. Could this be a situation where one or all of the tubes need replacing?
Thanks! Nick

[pdf64]

Unlikely to be a tube. How about if you just plug a cable between send and return?

[nickedm]

Thanks - I'll give that a try and see what happens. Nick

[nickedm]

Fender twin amp volume surge in effects loop

Hi there, tried plugging a lead between send and return jacks and amp worked fine, no volume surges or anything.

But when I tried plugging a Marshall delay stomp box into the effect loop the sound from the amp went all weird, volume drop and crunchy sort of woofly noise like a paper bag being scrunched up (just like it does with the Line 6 Pod plugged into it). But if I turn the mix control so that the effect is mixed out the sound goes back to being fine.

Here's the other weird bit - when I have an effect plugged into the loop I get electric shocks off the microphone when singing into it. Take out the effect from the loop and the shocks stop.

Can anyone advise?