Bell 2200 C schematic

[Rob Mercure]

Howdy Folks,


I've had the above amp in the attic for about 20 years "getting around to it" and am once again looking for a free schemo. Some of the other Bell amps I do have schemo for have a "sorta Mac-ish" cross coupled OT and this one has three wires from the OT that are unhooked so I wonder if this one has a similar circuit. Udderwise the amp is "restorable" but definitely needing restoration. So if anyone has a schematic I'd sure appreciate it.

Thanks

Rob

[Rob Mercure]

OK - got a copy thanks to Tom Bavis and here it is if anyone else needs/wants it.

Rob

[Enzo]

Wow, how old school and delightfully unusual. State of the art 60 years ago.

I see the heaters are elevated to the screen voltage!!! Not sure a 12AX7 would be happy with that?

Except the preamp tube, whose heater is part of the output cathode bias circuit. SO it is a 12v tube for that reason, while the rest are 6v. Why not, I suppose.

And that output stage cathode bias is great. Using the speaker winding for example is not so odd, but this has its own winding for the purpopse, adding some feedback, plus its center tap running through the preamp tube heater, then the return to ground through the grid balance network.

Gridleak phono preamp stage.

Feedback circuits just everywhere.

And how about all that B+ supply? Not to mention the extra filter stage for the preamp.

Pretty cool.

[Rob Mercure]

Yep, pretty fancy circuit - but, as fate would have it the schemo if for "2200" and I've got a "2200 C." One difference is that my amp doesn't use a 12SC7 with a DC filament for the phono preamp deriving the DC from the 5881 filaments but a 6SC7 with AC filament - same OT winding in the cathodes but a simple resistor. And, instead of that fancy CLCLCRC filter set up the chokes are replaced with resistors. Udder differences are an additional "gain" control along with the double ganged pot loudness control on the non-C schematic.

Unfortunately some previous person didn't seem to understand the circuit and the OT cathode winding is out of circuit and a few other changes have been made. Still the schematic was close enough and I can identify original early '50s wiring and the changes sufficiently to dive in when I want. Even with the "simplifications" it's still a pretty nice amp with a quite large OT and worth fixing up - wish I could find another to do stereo but I may use it for a small sub-woofer - if I ever decide to go to that trouble with my hifi system - to compliment the Scott 350B receiver that I use.

Rob