Can anyone help me u der stand what’s going on here? There’s two transformers whose secondaries are confusing..

 

Looks like both are wired in parallel to the rectifiers to increase the current. Both transformers would be identical, and secondaries would be have to be in phase.

 

Can clearly see two equal transformers with paralleled primaries (blacks) and paralleled secondaries (reds), paralleled filter capacitors and single bridge rectification to a transistor to control regulation.

 

So those four big lugs are the diodes? If so resembles a battery charger. And the 2n2076a, I can’t find a datasheet on it. Also the two bit silver guys must be caps but I’ve never seen capacitors with threaded ends like those.

 

The transistor is a PnP germanium type, looks like the Negative rail is being controlled, by varying the voltage on the base.

 

Hello,

Here you can find the datasheet:
https://www.datasheetcatalog.com/datasheets_pdf/2/N/2/0/2N2076A.shtml

Bertus

 

Also the two bit silver guys must be caps but I’ve never seen capacitors with threaded ends like those.

The cap on the left. Can type with threaded base. You just need to be old to remember them well.

Ron

 

I just disassembled an electronic counter that had the big capacitors with OCTAL plug in bases. It was a TUBE TYPE digital frequency counter, about 30 times the volume of my HP frequency counter. and it only was rated to 100KC. Lots of tubes, by the way.
AND, are those transformers really identical? one looks a bit thicker than the other one, but that may just be an illusion. And that lone PNP power transistor should have a better heat sink.

 

View attachment 324757

The cap on the left. Can type with threaded base. You just need to be old to remember them well.

Ron

Yes, and there were these types that used those octal sockets:

 

Thanks fellas.. this is super interesting. I don;t quite understand why you;d use two identical transformers in this way..more amperage, got it. But also perhaps the guy just did not have one big one.

 

So these are the rectification diodes then yes?

 

Hello,

There shoud be a type number on the diode.

Bertus

 

The two secondaries are in parallel to increase the available output current. The circuit is essentially one transformer, one diode bridge, two caps in parallel, and one emitter-follower output with a variable voltage to the base.

There is no reference voltage or feedback, so a percentage of whatever the cap ripple voltage is will appear at the output. The most simple mod to improve the circuit is to add an electrolytic cap from the transistor base to GND. Be careful with the polarity -- the + end goes to GND.

Is there any writing on either transformer or the pot?

ak

 

Yeah so TBH I stole these pics off a FB marketplace posting.. primarily because it was interesting but also to try to ID the circuit and parts. I figured the output being unregulated and likely pretty noisy.

 

The circuit is more of a reducer than a regulator. The output will be a percentage of the input, set by the pot.

ak

 

I thought that I sawa circuit for the assembly but now I do not find it. It would be simple to add a reference and make it a regulated supply, though.