Fx loop squeel issue... very frustrating

[GuitarDudeChris]

im trying to run some pedals through my fx loop but when i do, i have a loud pitched feedback sounding squeel that is constant when im not playing. if i try to run a noise gate/suppressor through the fx loop, i get a much louder and also constant feedback squeel... if i try to wite my noise supressor in an X pattern (through the fx loop and line in at the same time) i get no sound at all... im out of ideas and any help you could give would be appreciated. this is my equipment list:

Mesa duel rectifier trident stiletto stage II

fx loop- |line6 DL4, electro harmonix EQ|
amp input - |korg tuner, behringer noise supressor|

yamaha rgx520fz with duncan invader (bridge) dimarzio d activator x (neck)

 

[TheWarAgainstTime]

IIRC, the Rectifier has a parallel loop, so you're not able to run any kind of X-pattern with it like you tried with the gate. Not sure about the squeeling noise, though.

 

[sage]

You have to mod the effects loop to serial. It's hella simple. Basically, looking at the back of the chassis from the front once you've pulled it from the headshell, you see the "Mix" pot. It has three lugs. You unhook the left one and tape the end. Then you unhook the middle and right one and solder them together and tape or heatshrink them. Voila. Some dudes take the right wire and solder it to the wire on the middle lug. I guess they reckon it's easier to reverse (though, why would you want to?). This doesn't make it entirely serial, there is still a little bleed, but it will definitely solve a lot of the wackiness that happens when you're running modulation, delay, and reverb effects through the loop.

Did it on my Single Rectifier, took about 1/2 hour all told from start to finish. Totally easy, totally reversible.

 

[GuitarDudeChris]

when you say 'mix' pot, do you mean the knob that controls the level of the fx loop? i want to be sure before i start putting wires together...

heres a picture of the backside

http://www.mesaboogie.com/Product_I...tilettoTRIDENT/StilettoTridentHead-backLG.jpg