Budda SD-18, about 18 months old. Been running volume pedal in effects loop ever since I got it. Worked great until two days ago when I noticed significant signal loss. Unplugged "return" jack on back of amp and everything is fine. When I plug back into the return, problem is back. Tried two different volume pedals and the same thing. Pulled chassis and everything look well put together, no noticeable bad joints. Out of curiosity, ran patch in the effects loop and there is no signal loss. Tried different cords and same problem. Set the volume pedal aside and ran my board through the effects loop (I normally use board in front of amp and only use volume pedal in effects loop) and there is a signal loss. So, in a nutshell, when I use the effects loop, I have a signal loss and when it is open or patched there is no signal loss. I would have thought that running a patch would create the same symptoms of running a board or pedal in the loop, but it doesn't. Can't think this would be a tube problem and the jack itself seems to click OK, be soldered OK and works when I run a patch between send and return.