VoimaRadio K-40-2 Speaker Output

[Hank.3000]

Hi,

Might be a stupid question but where's the speaker output on this amp?

VoimaRadio K40-2

[Jon Snell]

THat is a Public Address Amplifier and as such is designed for 70 and 100voltline operation. The 18volt tapping is for a monitor speaker in the control room. There is no actual main power loud speaker tapping.

[Helmholtz]

I think the monitor output can be used to connect a 16 Ohm speaker giving up to 20W output.

The lower OT winding which also provides the 70V/100V line outputs is the "primary" of the OT connecting to power tubes.
The CT is grounded and the output stage uses 2 floating HT supplies.
Need to think more about this uncommon circuit.

I think it's a PP poweramp with tubes operating as cathode followers and the OT primary fed by the cathodes.

[Lauri]

It's a circlotron circuit. Speaker output is exactly where you have marked it on the schematic. With 8 ohm speaker you'll get about 40W out of it.

[Hank.3000]

Thanks!

I turned it up slowly for a short time, and I even get sound out of it.
But obviously it’s in desperate need of some new caps.
I can also see a crusty resistor in there.

All the can-caps probably need to go, do any of you know which capacitor brand/models that tend to go bad?
Or should I just swap them all?

Link to new pictures: https://www.dropbox.com/sh/7xdok5vmo...x0Lvx8zva?dl=0

Thanks again!

[Helmholtz]

It's a circlotron circuit.

Thanks, I had figured out the circuit principle.
But was wondering about the benefit from the cross-coupling.
That name gives me something to look up. Do you know a good source?

[Lauri]

Thanks, I had figured out the circuit principle.
But was wondering about the benefit from the cross-coupling.
That name gives me something to look up. Do you know a good source?

Main benefit of the circuit is that it doesn't require an expensive output transformer to get a good performance out of it. Power transformer with a correct turns ratio can be used as an output transformer.

https://circlotron.tripod.com/