Rectoverb effects loop noise

[Coldmonday]

I have a Rectoverb series 2 and sounds great without any problems except when I use the effects loop. When I use a delay or reverb pedal it sound fine for about 10 seconds then it starts making a sound like a fast vibrato. I tried the pedals on a different amp and they work fine. Any suggestions would be appreciated.
Thanks

 

[cyber104]

Try replacing Tube 4 (V4) - that controls the effects loop. I had an issue with running a reverb unit thru the effects loop where it would feed back terribly after 30 seconds - turned out the tube was microphonic

 

[Coldmonday]

Great thanks for the tech tip!

 

[Blaklynx]

If I'm not mistaken, there's delays between the split signal (being a parallel loop) which causes timing issues when they come together on the other side for final output. This is why some have converted the effects loop from parallel to serial. There's plenty on this site about this modification. It's pretty simple (really simple) to do if you're handy with a soldering iron. Off the top of my head; it's basically removing two wires and resolder one of them to another tab on the pot and leaving the other disconnected. Just do a search to be sure.

I own the same amp and run a reverb through it. I haven't modified my amp as I haven't heard anything strange. Maybe with delays in the loop it's more noticeable.

Somebody correct me if I'm wrong.

 

[Coldmonday]

Wow, cool thanks for the info!

 

[Coldmonday]

Try replacing Tube 4 (V4) - that controls the effects loop. I had an issue with running a reverb unit thru the effects loop where it would feed back terribly after 30 seconds - turned out the tube was microphonic

I tried replacing the 12AX7 in V4 and the vibrato type noise continues. I also tried replacing each of the 5 12AX7's one at a time to see if it was another tube, but the noise continues as well.
Thanks