Problem with my FX Loop?

Hi everyone,

I am new to Mesa Boogie and I have a question I am hoping you guys can help with. I recently bought a Mark V and paired it with a Rectifier 2x12. Everything was working great until I decided to build a new pedal board and now I am having issues. I have interference on all channels though that isn't as concerning as if I run anything through the FX loop. If I do I get very little volume and a lot of distortion even in Channel 1. Before I put the pedals on the new board and had them running the same configuration everything was fine and I am not sure what I did wrong. Loop Send level is in the middle. If I bypass the loop all I get is a bit of interference but it sounds great.

I have a pic of the set up below.

I am running the guitar > Wah > NS-2 Input > NS-2 Send > CS-3 > TS9 > Cyber Demon > NS-2 Return> NS-2 Output > Mark V Input. This is working though I have more interference than before, I may need to move the power supplies and cables.

The FX loop is driving me nuts. I am running FX Send > Drop > DD-7 > CE-3 > MT-2 > Return. Again, very little volume and tons of distortion whether the pedals are on or off.

Any suggestions?

Thanks!

https://imgur.com/45v0lSh

Some ideas...

For the loop, try adjusting the FX loop level (knob on the back). You may need to turn it down a little. If I remember correctly, it is a little hot if set it the center detent, especially for pedals that are designed for instrument level signals.

Are the pedals powered by isolated power supply sources? This could be a source for noise and interference.

Troubleshooting by removing all pedals and adding one at a time may help isolate a pedal that is not playing well with others.

Thanks Jaslan.

I replaced the cables and tried each pedal one at a time and all I pick up is a hum and a very quiet distorted sound. Adjusting the volume in the back of the amp doesn't do much aside from raise and lower the hum.

I am wondering if I somehow blew a tube I don't know what else it could seeing as how it worked before I moved everything to this board.

I was able to get rid of most of the interference by moving the instrument cables away from the power cables.

Yeah, it could be a tube. I don’t remember which one powers the loop but the diagram should show it. Perhaps try swapping that one out with a spare if you have one. If you don’t have a spare, try swapping with a CH3 tube or reverb tube and see what happens. If you suspect a bad power tube, try 45 W mode to to isolate two of them, and then swap those two pairs to isolate the other two (keep the pairs together, i.e. inner and outer pairs). Beyond that, and doing a full re-tube (which is expensive and not guaranteed to fix the problem unless you have found bad tubes), I don’t know what else to advise.

Oh wait, troubleshoot for bad cables if you haven’t already.

I was able to fix the issue with the amp today. I replaced preamp tube V4 and the FX loops is working like a charm

Thanks all for the help!

Off topic. Whats your pedal board model? I need a mew one.

I built my own out of a bunch of wood I had left over from a couple projects.

Ok nice.

jmkratt said:

I was able to fix the issue with the amp today. I replaced preamp tube V4 and the FX loops is working like a charm

Thanks all for the help!

Click to expand...

Nice!

Well it was nice. Worked well for a couple hours. Turned it back on and the problem came back. I get a very low distorted sound regardless of channel or where the send level is. Only happens when the loop is active. If I hard bypass the effects loop when I do the amp works fine. Either a blew another tube, again after a couple hours, or there is something wrong with the amp I figure I think I am going to need to get it serviced...

I had a low hum going on with my pedalboard.

I found out it was coming from patch cables going into my 4 way jack seen here:

https://www.amazon.com/gp/product/B01AAFPNJM/ref=ppx_yo_dt_b_asin_title_o06_s00?ie=UTF8&psc=1

My patch cables were those right angle, pancake type ones but they were touching each other. I put some electrical tape on these pancakes and the hum disappeared. Maybe ya got some weird grounding or input/output loop causing the hum.