Mesa RK 1 - master doesn't work?

[IkarusOnFire]

Hello people!

I've a rather odd problem. My Mesa Road King 1's master/loop/solo setting has stopped working. That is - whenever I have the "loop system active" switched on, there is no sound whatsoever. Neither of the 4 channels have anything.

When I switch it onto "bypass" I have all the sound I need - all four channels work perfectly.

What might be the problem? I'll list the setup:
1) guitar - cable - amp
2) NO pedals, nothing plugged into the loop system
3) King Kontroller works perfectly fine
4) All tubes have been changed recently - and I have checked all the tubes for any defects (I have a spare set - I have taken out one tube, replaced it with the a new tube, tested, done it again on the next position/tube)
5) I have tried connection a cable from send to return with no pedals attached to check if any sounds should reappear. Nothing.

Has anyone experienced this problem? I've played gigs with it, like it is now - only working with the bypass switched on - and that's okay - but I actually use the "solo" switch and the master vol control (or used to anyway) and would like to use the loop too.

What else can I do?

Thanks in advance!

 

[eaeolian]

Wow. Call Mesa. I'd usually say it's the loop tube, but I'm not sure about this.

 

[noodles]

Hmm, that is weird. Do you have Mesa preamp tubes, or something else? The cathode follower spot tends to be really touchy about tubes, but that would only effect ch3 and ch4 (that was the problem I had). Try replacing the loop tube, too, since it sounds like it might be screwed. Also, the bonehead questions: is loop set to on on all four channel banks on the back, and are the loop volume knobs not set to zero?

 

[noodles]

Oh, and drop into Grailtones and post your problem in Modern Amps/Rectifiers.

 

[IkarusOnFire]

Thanks! Loop tube...Is that one tube in particular, or how is that?
I can't post my problem on the boogie-board - I only have a gmail addy- and they won't accept that as a member e-mail.

The loop has been switched both on and off on all 4 channels on the back (I usually control it with the footswitch).

 

[eaeolian]

In the RK, the loop tube is V4, I believe.

 

[IkarusOnFire]

I'll try replacing that one alone Just tested the 5u4s - they're good - tested that no signal comes from the send loop when I attached a cable (tapping the point of the cable attached). No luck, I'm hoping the v4 will do the trick. Cheers!

 

[Enselmis]

Maybe one of the jacks for the effects loop in/out got messed up somehow? That's my only guess.