Help identifying vintage amp

[sgelectric]

The "mystery part" is a bias cell.......I once found one in a MOTS 1940s Dickerson lap steel amp.

Bias Cells

[Enzo]

You have a power transformer and an output transformer. Those should be easy to identify. A power supply choke would have obly two leads coming out, and the remaining this? COnsidering the era this unit came from, it could easily be an interstage transformer, a phase inverter for example. Draw up a schematic, all should become clear.

[NFXP]

as soon as i get a few hours ill draw up a schem, it might be awhile til i get a few free hours but never the less.

[NFXP]

This amp on ebay has the same indicators bezels, it seems to be a no name amp even though hes saying its a RCA or Silvertone, maybe those bezels are generic parts for the era.

[Enzo]

Yes, dial plates were a stock item, and the same ones could be found here and there.

Maybe less today, but here is one company's current product:
http://www.electro-nc.com/rotaryus/knob.pdf

[soundguruman]

It's an Operadio amplifier, attributable to J. McWilliams Stone. The company later became DuKane...They drew the blue print for all guitar heads to come in the future. All guitar heads are copies of Operadio.
The amp (typically) has a pentode 6J7 preamp that grinds like a chainsaw, unbelievable sustain and distortion that puts modern amps to shame.
(if you think that Mesa Boogie invented high gain guitar amps, you are wrong, wrong, wrong) This high gain tube amp was around before Randall Smith was born.
The amp is very rare and hard to find, however Sam's photofact schematics are still around and can be had for this unit. It will take some searching
Sound quality? there is nothing like an Operadio. Play it for a while and you will throw all distortion pedals into the trash can. Don't need them anymore.

[NFXP]

This is the only Operadio i could find that looks similar. But since all the parts in my amp are made in Canada i doubt its going to be a American based company. Theres a better chance of it being a british company based in Canada. Canada had its own companies making electric products (radios, fans, etc) similar to the ones made by large companies in the States. unfortunately theres not much information on those companies. My search continues.

[soundguruman]

Well, Operadio did make a lot of different models, but it could be Stromberg Carlson, Masco, there were a lot of similarities. It sure looks like an Operadio on the inside, see the vertical circuit board? I have worked on Operadios, and that is very characteristic of that manufacturer. So is the pilot light holder...
Anyway, it's very cool, and I would try to restore it and get it back to working. The 6J7 preamp tube has a killer grind.
The best source to see pictures of operadio is the sams photofact manuals. Most of the other documentation has been lost to time.

[Prairie Dawg]

It was quite common in the past for American electronics companies to set up operations in el Norte to build their slightly different products using components made by Canadian operations of American companies like that Aerovox capacitor.. I have a GE radio that was made in Canada, all Canadian components, and I put a very similar American made chassis in it with minor modifications. All the dimensions were the same.
Any way you slice it it's a cool amp.