Help! Randall RG100ES XP Effects Loop Problem

[cdshot10]

I have an 89 RG100ES XP full stack that is having a problem with the effects loop. Everything on the amp works perfectly and is in good condition, but when you try to hookup an eq or sonic maximizer, basically anything in the effects loop, it produces a static noise into the output of the amp.

The maximizer used to work fine but I think someone tried using a metal zone pedal in the loop and that is what caused this problem. Before this happened the maximizer would show that it is correcting the signal, but now it doesn't do anything but it still works on my other amps. I am fairly familiar with electronics if someone could point me in the right direction to what I should test or replace on the board.

Thanks, Chris

 

[Vince]

You need to get it serviced.... never put a boost in a loop.

 

[billymagnum]

i dont know about putting an eq there but a sonic maximizer should work fine. maybe the eq killed it....

 

[cdshot10]

Its really odd that the amp sounds fine with nothing in the loop. I tried hooking up a noise gate through the loop and there was no output from the amp at all even with the threshold all the way down.

I was looking over the schematic and I can't figure out what would cause this being its just a parallel effects loop.

 

[Matt42]

I have an 89 RG100ES XP full stack that is having a problem with the effects loop. Everything on the amp works perfectly and is in good condition, but when you try to hookup an eq or sonic maximizer, basically anything in the effects loop, it produces a static noise into the output of the amp.

The maximizer used to work fine but I think someone tried using a metal zone pedal in the loop and that is what caused this problem. Before this happened the maximizer would show that it is correcting the signal, but now it doesn't do anything but it still works on my other amps. I am fairly familiar with electronics if someone could point me in the right direction to what I should test or replace on the board.

Thanks, Chris

Did you ever figure this out? I’m obviously 13 years late to the party here but I’m having the same exact issue with an RG XP series. It’s driving me nuts. Did you ever figure out what it was?