Best regards to all. My name is Yuri. 10 years ( for all parts) I'm looking for the source of this circuit! without any results ...... Circuit has four transistors ( AC125 , AC126 and 2x AC128) pcb board -code is ( 022 C )--- As a guide, the circuit was found at London (in the bin of garbage and have an very important story - is used as an amplifier of an famous guitarist as studio amplifier for guitar( even he ,does not know the origin of this circuit ) - It circuit is founded year about 68'-72 ' + or - . !. has power about less an 1 watt - have 2 transformers (push-pull)., the output transformer is very unusual, never seen extra windings with 7-pin out transformer ) - For me , this not an radio , I think (my best guess maybe audio device for mic or baby alarm , ). Any indication. Any indication ??? Many Thanks

Another foto(I have no other) Thanks

Welcome to the ARF forums !

Doesn't ring a bell, but the circuit might be from about 1964 or just a bit earlier.
Thats the time frame when the AC series of transistors showed up in pocket radios.

~ Mitch ~

Hello Mitch Thanks!. time frame? pocket radio 64 ' uhmm ? After 10 years of researches this indication does not match - it is unusual audio circuit

Ahh...you are looking for info on the origins of the Deacy Amp, from Brian May of Queen.

http://en.wikipedia.org/wiki/Deacy_Amp

Good luck finding info on what it is.

Everyone knows this - useless

To me, this looks like the audio output module in a Nordmende (lunchbox size) transistor radio I once had. I believe an extra secondary winding was used in conjunction with a negative feedback circuit.

Dave

Without outright identifying it, it's a guitar practice amp from the early 70s.

Thank you for assistance! But (practice guitar amp 70 ') clearly does not match - Normende uhmm, maybe (after all these years, I had looked only yours all transistor radio - does not match the design of a transistor radio (unfortunately) ....Sometimes I think - an audio device with long wire connected

I forgot to say- this circuit have , three (feedback) reactions !

If it IS a Deacy amp (or replica) this info might help?

"The Deacy Amp circuit is a 1950s audio style Germanium transistor push-pull circuit, utilising in its front end an AC125 and AC126 respectively, with the push-pull Output stage comprising two AC128 Germanium transistors.
It also features a Driver Transformer and an Output Transformer and is similar to several designs of the time, which can be found in the Mullard Reference Manual of Transistor Circuits (see pages 168, 170 and 171)."

I know the story, I studied All These circuits (an indication That does not mean anything) - Mullard does not match, absolutely. Not is it -. would simple for me , if I so

Agree with Yuri-life would have been so much easier if it was a Mullard amp-but it isn't.Just do a component count and you'll see why.
It's a pity that we don't have better pictures than these.
The output transformer might well have up to 7-8 connections if it has several feedback windings(Bush TR82C) or multiple tappings like Telefunken Bajazzo.I've also seen dual output windings connected in series which increases the number of connections.

Thank you! To clarify, this circuit , output transformer has 7 connections !- Yes I confirm ! this would be the right way to identify !

Given this is not a transistor radio, can a moderator move this thread to the Clubhouse?

~ Mitch ~

I saw that story that stated it was a 1950s device, but I would assume it would have carbon composition resistors on it, not carbon film resistors. And when did those green epoxy coated mylar capacitors first come out?

One thing to remember, this has been modified by John Deacon of Queen, and some of the wire connections are probably not original. You can also see where some holes are missing wiring. Since this was found in a trashcan in London in the early 1970s, and I think the AC transistors were used in England I'd look for a device made in England circa 1960s-1971 (year it was found).

BTW, the number on the board is 055C, not 022C. The board is upside down in the 1st photo.

Looks like 022 C. The first picture in the listing appeared to have been reversed when compared to the pictures from the top side of the board.

Right! I was wrong to set this picture. as the board is completed and not cut or Salvaged from a larger PCB, My personal theory Is that this unit was part of oz baby or an alarm listening device, and similar devices ... the type where you installed a small microphone in the cot and had the amplifier and speaker unit downstairs linked by yards of cable.

Interesting circuit but it's still not a transistor radio.
Dave D. - Can we move this thread to the Clubhouse?

~ Mitch ~

It may not be a Transistor radio, per se, but it is still a solid state circuit, and IMHO should stay in this particular forum.


Where are you from, Yuri?