Help understanding schematic I traced from point to point wired, mystery tube device labeled “non-linear amplifier.”

[AardvarkBry]

My guess is varistors, which change resistance with voltage. That will make it non linear for sure.
Also you have no grid leak resistor to ground from the control grid of the second tube. Another 470K which seems to be popular?

Something should be there. Do you have a scope? That will tell you a lot.

Whatever that is used for it appears to have a lot of gain with 3 pentodes in a row.

I need to get a scope. Can you recommend a good, relatively affordable one?

 

[emrr]

I’m like 90% sure the output transformer is a Peerless. There’s no label, but it looks exactly like one. It’s got the exact same casing. I’m not sure what the impedance is though? I don’t know much about cathode followers. I’m very confused by them. They have a very low impedance output, like 400ohms, but they want to see like 100k? The input transformer is a very nice looking 600:50k Hollytran.

It's probably also a Hollytran. Good stuff. Not much of it out there. Many transformer shield cases were made by Craft in the US, if you see their ads you recognize the types across many brands.

 

[AardvarkBry]

It's probably also a Hollytran. Good stuff. Not much of it out there. Many transformer shield cases were made by Craft in the US, if you see their ads you recognize the types across many brands.

Yeah, I haven’t seen very many of them.

 

[Mr. Moscode]

I thought varistor too, but I wasn’t sure whether or not they would measure a resistance. The only circuit I’ve ever seen them in, were the old Magnetone amps, where they used them to make the tremolo. Maybe this could be some very early diode clipper limiter?

I seem to remember them in tube TVs before solid state but that was long ago and used to be. Diodes of the era of this gizmo were selenium and or vacuum tubes.

TO Aardvark: If you don't have the know how or test equipment to identify it then search the web for a schematic or service manual.

The cathode follower in this case merely adds current to the incoming signal at the grid and has a slight loss around a db or so of voltage. It drives a single ended output transformer. Fairly uncommon to see this but not exotic.

 

[rock soderstrom]

I need to get a scope. Can you recommend a good, relatively affordable one?

Some ideas
I need a new oscilloscope - 300€?

 

[AardvarkBry]

I’ve been reading this “Basic Electronics Navy Training Course,” from 1955 that I found on the national archives website, and the whole section on limiters, is almost exclusively about using diodes, and in particular silicon diodes. Then I found this ad in International Rectifier 1960 catalogue.

That training book is an awesome resource for tube design, if anyone is interested: https://ia802709.us.archive.org/14/items/BasicElectronics10087A/BasicElectronics-10087A-1962.pdf