Mesa DC30 Help!

[WolfBall]

Hello, my first post and my first Mesa. I just picked this baby up from a used store here in Ottawa. I went through a lot to get this thing, had to sell one of my guitars, anyway I am having a few problems and I am afraid I may have to bring it back. Now since the amp was on consignment, there is no warranty, however I do have 3 days to try it out, and so far day one hasn't been good to me. Visually the amp looks immaculate. Now here are the problems.
1) When turning the Standby switch on/off, I hear a popping sound, kinda scary. It is kinda loud...
2) This amp does not like my M13 at all. I did as the manual said (turn the effect mix high, adjust the wet/dry on amp) however, the pre-effects, do nothing, at least as far as I can tell. For example, I wanted to add a little boost for leads, tried, OD, Boost Comp, etc, but no difference...so far I can live with these troubles, since I purchased this as a back up amp.
3) Here is the biggy. The amp seems to loose and gain volume (phasing in and out). At first I thought it was the Effects Loop. So I tried the guitar directly into the amp, and the problem was still there. This was after about an hour or so of playing with the amp. I really want to like this amp but I don't know, any thoughts? Thanks!

 

[WolfBall]

Now I am trying it out again, without anything but the guitar plugged in. I noticed that in the envelope of documents, a red tag talks about shielded and unshielded Footswitch chords. Now I only have the Lead/Rhythm foot switch, yet the chord appears to be a regular guitar chord...would this cause some problems...anyway I am going to try my M13 now without the footswitch, see how it works.

 

[WolfBall]

Ok so I have been playing since I posted. Tried the M13 out and it worked great, what a difference with Parallel vs Series ...anyway it was working fine, but it just started like 2 minutes ago. I believe it has to do with the heat. Once the amp gets hot, it starts to affect the sound, causing the amp to increase and decrease in volume, dang I was really starting to like it!

 

[Monsta-Tone]

Not sure if you still have the amp, but....
This problem is usually tubes or cold solder connections on the power tube circuit board. Either way, it's a pretty easy fix.

Most of the guys here seem to keep their DC-3's away from the wall or aim a fan into it when they play because of the heat issue.