1940 Operadio military theatre Model 830-A amplifier conversion - Opinions?

[Beyond Blues Driven]

I've just recently purchased this beauty, and after scouring for hours on these forums, I've decided to put it out there, in hopes of obtaining useful information about it, that I wouldn't be able to discern myself, as I am not a technician yet, school starts in September.
I'm not looking to start an opinion war on wether PA heads, and they're ilk, are necessarily good/useful/cost effective/etc, as that has been worn out heavily.
For me, a $100, is a small investment to make on something that is actual war material, hand wired, and full of old school tubes. I'm not going to gut it no matter what, so if it's unuseable, then it becomes an antique conversation piece.

There is a unique ohmage selector that goes from 2-500 ohms, with a small 5pin connector.
The selling features to me also, are the fact that there is already 2, 1/4" inputs, a High eq know, and a Low eq knob, and a Volume knob that goes to 20!! Sold!

There is a High/Low switch, tube complement is as follows;
6J7 - 6J7 - 6SQ7 (although the tube socket says 6C5) - 6C5 - 6L6G - 6L6G - 5AS4A.
The strange thing is the 8" field coil that was attached to the top of the unit. Would operation of the unit rely heavily on the speaker, and the leslie-type cable attached to it? Does the circuit look good, or is it unsalvageable ala bob?
With the pic's I've provided, what are your opinions?

[SeanF]

the field coil was typically used as a choke in the power supply; something needs to be there. I think most people substitute for it with a resistor, but a choke would be much better, as those old amps had very small filter caps.

It uses a transformer for the phase inverter; it's a clean machine.

The output transformer is pretty impressive; anything from 2 ohms up, wow.

The 6SQ7 doesn't appear to be a direct substitute for the 6C5; does it look original?

I wouldn't trust any of those old capacitors.

A buddy of mine's got a much more complex Army PA amp of the same vintage; apparently they sprayed the entire interior with lacquer after assembly, to keep water out. pretty wild.

I'm sort of interested in this because I'm looking at a Silvertone PA amp of a slightly earlier vintage that uses much the same tube complement, and trying to figure out what to do with it. No 1/4" jacks, though, it's all the old 5/6-pin sockets. I'm going to order some of those plugs to fit those sockets, and see what I can do with it. Should be interesting.

[Beyond Blues Driven]

I suppose I'll have to get the cone redone if it is optimal as the choke.
Everything LOOKS to be original, although the 6SQ7 inmention is in a metal casing, whereas all the rest of the tubes are in either the black plastic, or classic glass, so I suppose that could be an indicator, although the socket doesn't seem to have been modified/altered in any way.
I didn't realise Silvertone made PA head's aswell, I'd love to see some pics, just to compare. I haven't seen too many units with the 5/6 pin sockets.

[SeanF]

the transformer phase inverter isn't original, it's smaller than the original, and was badly tacked in, since the bolt holes didn't line up; I already took it out. I've got 3 6J7's, a 6C5, a pair of 6L6's and a 5Z3 rectifier. I'm probably going to end up gutting it and building a new circuit; no schematic, and it's been modded a bit, so I'm kind of trying to figure out what it was originally. What's left of the original wiring was really well done, shielded cable on all the grid leads, nice PTP work, but somebody's blobbed over and tacked onto it with what appear to be extra capacitors. really nice power and output transformers. The line voltage input is interesting; it's got a jumper you can use to select between 125, 250 or 500VAC. That plug goes to a transformer that feeds the power supply.