OK...back at it.
7C7, 7F7, 2x6L6 and 5Y3G tubes, all strong except a slightly weaker 7F7. Definitely needs caps. Will rewire any cloth-covered wiring that I can, because the existing stuff is kinda...fuzzy (presumably from moisture/mildew). The choke and OT paper are also kinda funky-looking, but they are dry, and they measure fine. I THINK the power transformer may have been changed a some point, because it looks like they had to slightly cut and fold the chassis hole to accommodate it. Still, definitely old.
So, I checked everything, plugged it into a Variac, and turned it up slowly. Got it up to 115V, no problem.
(Downloaded schematics from a search of this site. Thanks, Bruce Collins!) http://music-electronics-forum.com/a...oma17schem.pdf
Actually fairly quiet (self-noise) with signal generator connected to "Phono" input. Also, not very loud (naturally).
Way more noisy connected to "Microphone" input. Hopefully, all new caps and a grounded plug will cure most of that. (Definitely needs at LEAST those...touching the chassis produces way more hum, and is kind of worrisome.)
So, knowing it kind of worked, I rigged my Strat up to the "Microphone" input. (This has the old screw-on mic connector for that, and a terminal strip for the "Phono" input.) There's some tone under all that noise...and it's surprisingly loud through those speakers! And, those speakers seemed to take it with no problem.
Now then, some questions. I know blues harp players seem to love these things. Would it be sacrilege to mount a 1/4" jack in the front. (That's actually really close to the tube pin where it connects, anyway.) I've seen people put them in the back, but I think it would be handier on the front, and there is plenty of room in there. Should I leave the back screw-on connector connected (with a new cap) and install a front jack, with the same value cap? Would a different component setup be better for guitar? If so, would a switch installed to toggle it from the "Mic" to the "Guitar" setting be out of the question, with the components for each.(To use as a harp amp, or guitar amp.) Does it even matter?
What to do with the "Phono" circuitry? Obviously, it's much lower. Would it make sense to install a 1/4" jack for that, and maybe run a boosted signal into it? Maybe, "Y" the guitar, one going straight to "Mic" input, and the other going through a boost/preamp/etc...and maybe even through something like my Fender Reverb Unit? Set the Fender wet, and dial in the amount underneath the straight signal? Maybe, run an overdrive under the straight signal, and mix to taste? Can that be done? Would it make sense to try?
I assume I'll just leave the speaker sockets on there, and parallel a couple 1/4" jacks by them. The system still has the funky old speaker plugs, which I'll rewire with new (non-cracked) wire, and use when I use those speakers with it.
About the speakers, am considering mounting some feet tall enough to clear the handles, so I can set on top of the other. That would make the "stack" about 40" tall, and get the top one up a bit. (They are so light, though, I wouldn't put any amp on top.) Am wondering, even, about installing some board on the backs of one, or both, to make them semi-closed? (That'll be easy to goof with, before doing it.)
One other thing. I've read that those 7#7 tubes are a bit funky, and a lot of people change them to 6S?7 (along with the sockets). I'm going to try to keep it what it is for now. I can always screw with that later. But, what is the main advantage of changing those out?
Any ideas or comments appreciated. Any "NOOOO...DON'T do THAT!", also appreciated.