OK, things are straightening out nicely. Pulled the back off the amp cab and guess what I found in the bottom?
Yep, one of the big transformer mounting screws! I put it back in and tightened the others. Would it be wise to put some star washers under these things? I think so. The rest of the screws in the chassis seem to be tight.
As for the tubes, they are fine also. Nice and tight. Dumb question: are the bent metal rings supposed be holding the tubes in? Cuz if they are, they are barely contacting the sides of the tubes' bases. Just wondering.........
I played the amp after tinkering and it sounds fine. If I stick my ear next to the back, I can hear faint vibrations when I hit a note at volume, but nothing significant. When play at a moderate volume and sitting in front of the amp, I can't hear anything. So, I think that's cleared up.
So far, so good! Going to check the chassis screws in my other MM amp next!