RM4 Issues - Series Loop RM4 cutting out, noise

[rhequiem]

Hi all. I've been having a weird problem that I just started heavily troubleshooting tonight, and I wanted to get your opinions on what it might be. Here's the story:

I bought a used RM4 from a forumite here (Phloyd) and so began my journey into MTS. I got some modules, everything worked well. Later, I wanted to add effects to my RM4, so I bought a Line 6 M13. I originally had it plugged into the parallel loop, and everything worked fine, though I didn't like the sound so much with the effects knob. So, after reading how most RM4 users tend to run their effects through the series loop, I moved the M13 over there, and could tell the improvement. However, jamming with my band a few weeks ago, my sound suddenly died - or nearly died, it got *extremely* quiet. After fiddling around with cables, I noticed the sound would come in and out when I wiggled one of the cables going in to the series loop. After some fiddling, I got it going and didn't really give it much thought. Tonight, while practicing, I noticed that there was some significant noise happening when I played single notes on the 5/6 strings. At first, I thought it was only in my Dr Feelgood module, which caused me to switch tubes in it, move slots, etc. None of that helped. The noise would stop when I put my M13 in bypass. So I plugged in an ART SGX2000 that I have here and there was still noise. After plugging in my M13 again, the sound was very very quiet. So I started unplugging cables, and as soon as I unplugged a cable from the series loop BOOM my sound came back.

So I think I have some kind of issue with my series loop. I opened my RM4 and only noticed one thing that seemed unusual - there was a red/black 2-pin cable hanging loose. I saw 2-pins sticking up on the left side of the board, but didnt see the usual plastic housing that would indicate that the plug belongs there. I took a picture of it and thought I'd share it here to see if you might be able to offer me some thoughts as to what's going on and how I can fix it. Thanks!!

 

[rhequiem]

I've been playing around with this some more, and I am not so sure it's the series loop. I plugged the M13 into the Parallel loop and I heard the same "static" when I played single notes on the 5th and 6th strings. It completely goes away when I have the M13 in bypass, so I'm wondering if it's something going on with the M13... Maybe a line level issue? I'm still pretty new to all of this, so I'm kind of running around in circles trying to figure out what's going on.

 

[SacredGroove]

When you tried the SGX, did you use the line level (+4) in/out? FYI, the m13 is instrument level, so the noise probably should've happened when you used your parallel loop initially.

 

[rhequiem]

Actually, I didn't... I have been playing with this some more, and think I have it figured out. Like I mentioned, I am new to tube gear, and I think I might have this narrowed down. Basically what I was doing was running my RM4 master at 2:00-3:00 and my modules at about the same and then keeping my power amp really low, like 8:00. I think this was just causing too much breakup in the sound. I found that if I turned the master on the RM4 down to like 2:00-3:00 and the module masters to like 9:00-10:00 and then up the volume on the power amp, it reduced the static. I tried the M13 in parallel, series and in front of the power amp and still got the static on single notes until I reduced the masters on the modules and RM4 a bit. Without the M13, I can roll the masters up as high as I want and it's clear, but I think the M13 can't handle all that tube power coming from the RM4 hehe

 

[dboy5150]

I had static in the series loop once; turned out to be a bad series buffer tube. I replaced all three tubes just in case and keep a couple spares around.
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