3 valve 1920s set - UK Vintage Radio Repair and Restoration Discussion Forum

Colin-M5FRA · 9th May 2012, 5:03 pm

I have come across a complete 3 valve wireless with horn speaker. It looks to be in very good condition apart from a think layer of dust. It is built into a nice wood veneer cabinet with room for batteries below.

There is still an Ever Ready G.B.4 9v bias battery connected. I have some photographs and would like to identify the circuit so that I know what the rear connections are.

The idea is to clean it up, test the components and then apply power. I have a nice 100v stabilised DC PSU for the HT and can use batteries for the heater and GB supplies. So, can anybody identify the set? Does anybody know of the circuit used?

Boom · 9th May 2012, 5:54 pm

Hi Colin. The horn is a BTH C2. I have one of these and they sound really nice.

The set is TRF and might well be home made as many of these were. It will use a more or less bog standard uncomplicated circuit.

I'm sure someone will correct me if it is a commercially made set but I don't think it is.

HTH

Ah!:- I have just looked and it is identical to the layout on my set but the cabinet is different. Before you do anything check the windings on that transformer for continuity.

lesmw0sec · 9th May 2012, 6:39 pm

Also worth checking the grid leaks for value, they may well have turned into high class insulators! Bit of a job to see what goes where through the dust. As Dave has said, sketch out the circuit and you can probably see what is what. Looks like a regenerative detector followed by two stages of A.F.

Ed_Dinning · 9th May 2012, 7:11 pm

HI Colin, when you have removed the dust see if there are any names on the large coil. That may give a clue as to its origins.

Ed

Peter.N. · 9th May 2012, 7:53 pm

A very nice set in 'original' condition, I wouldn't be surprised if it still works, there were lots of sets like that about when I was a kid but not many left, especially in that condition.

Peter

Boom · 9th May 2012, 7:57 pm

The grid leak was indeed o/c on mine but you can open them up and pop a small modern resistor inside. Beware the markings tough (though). Mine were not the same as modern components. What I read as 3 Ohm was actually 3 MEGohm!

AC/HL · 9th May 2012, 8:03 pm

It's a 1927 Cossor Melody Maker, the first of a long line of radios.
They were sold as a kit, but the cabinet was made by various manufacturers.
It was a three triode design, but a SG add-on unit was available. Later, a modification was released to convert the 1927 MM to screen grid. Yours is the original with the large tuning coil.

PS Dust is always a good sign!

Herald1360 · 10th May 2012, 12:53 am

Quote:

Originally Posted by Boom

What I read as 3 Ohm was actually 3 MEGohm!

There was a convention where Ω (omega) represented megohms and ω (omicron) represented ohms.

Maybe that explains things.....

Colin-M5FRA · 10th May 2012, 6:30 am

Quote:

Originally Posted by AC/HL

It's a 1927 Cossor Melody Maker, the first of a long line of radios

Thanks to all who have replied and for the definitive identification. Can't wait to see if it still works! I have a vague feeling I stripped one of these as a kid - too many years ago! I recall having a collection of components similar to these.

Colin

julie_m · 10th May 2012, 9:34 am

Quote:

Originally Posted by Herald1360

There was a convention where Ω (omega) represented megohms and ω (omicron) represented ohms

Actually, Ω is an upper-case Omega and ω is a lower-case omega (yes, the ancient Greeks had capital letters). The Greek letter Omicron (in both cases) looks the same as a Roman O.

AC/HL · 10th May 2012, 9:11 pm

Quote:

Originally Posted by Colin-M5FRA

Does anybody know of the circuit used?

There never was a circuit as we know it today.
You used a full size drawing to lay out the parts on the baseboard and Ebonite front panel. The drawing also had full size impressions of the wiring, which were cut, bent and sleeved beforehand. Then it was simply connected up and away you went.
The attachments are sections of the instructions that were kindly supplied to me by a forum member some time ago. They aren't complete, but I think they have all the information you need to get it going.

Herald1360 · 11th May 2012, 2:55 pm

Quote:

Originally Posted by ajs_derby

Actually, Ω is an upper-case Omega and ω is a lower-case omega (yes, the ancient Greeks had capital letters .....) The Greek letter Omicron (in both cases) looks the same as a Roman O.

Well I only managed a 9 in Greek O level......

Colin-M5FRA · 15th May 2012, 5:37 pm

Thanks the diagrams certainly helped. I did some checks today and the secondary of the transformer is open circuit. It's a Ferranti AF3. What are the chances of getting a replacement?

Colin

Jim McLay · 17th Apr 2015, 10:58 am

Hi Colin,

Did you end up finishing this set restoration? That transformer could be rewound although it's probably got thousands of turns of fine wire. I found an article in Practical Wireless May 1980 where Robert Thorton reported getting reasonable results using a small 20-0-20 V mains transformer as an intervalve transformer giving a step-up ratio of about 1:6. This is what I'm trying out in a TRF (you can see the thread so far on https://www.vintage-radio.net/forum/...php?p=745268)- I'm always hoping to finish making the parts!

9th May 2012, 5:03 pm	#1
Colin-M5FRA Retired Dormant Member Join Date: Jan 2011 Location: Sheffield Posts: 9	3 valve 1920s set I have come across a complete 3 valve wireless with horn speaker. It looks to be in very good condition apart from a think layer of dust. It is built into a nice wood veneer cabinet with room for batteries below. There is still an Ever Ready G.B.4 9v bias battery connected. I have some photographs and would like to identify the circuit so that I know what the rear connections are. The idea is to clean it up, test the components and then apply power. I have a nice 100v stabilised DC PSU for the HT and can use batteries for the heater and GB supplies. So, can anybody identify the set? Does anybody know of the circuit used? Attached Thumbnails

9th May 2012, 5:54 pm	#2
Boom Retired Dormant Member Join Date: Jan 2007 Location: Westbury, Wiltshire, UK. Posts: 2,451	Re: 3 valve 1920s set Hi Colin. The horn is a BTH C2. I have one of these and they sound really nice. The set is TRF and might well be home made as many of these were. It will use a more or less bog standard uncomplicated circuit. I'm sure someone will correct me if it is a commercially made set but I don't think it is. HTH Ah!:- I have just looked and it is identical to the layout on my set but the cabinet is different. Before you do anything check the windings on that transformer for continuity.

9th May 2012, 6:39 pm	#3
lesmw0sec Octode Join Date: Jul 2009 Location: Carmel, Llannerchymedd, Anglesey, UK. Posts: 1,507	Re: 3 valve 1920s set Also worth checking the grid leaks for value, they may well have turned into high class insulators! Bit of a job to see what goes where through the dust. As Dave has said, sketch out the circuit and you can probably see what is what. Looks like a regenerative detector followed by two stages of A.F.

9th May 2012, 7:11 pm	#4
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: 3 valve 1920s set HI Colin, when you have removed the dust see if there are any names on the large coil. That may give a clue as to its origins. Ed

9th May 2012, 7:53 pm	#5
Peter.N. Dekatron Join Date: Jul 2008 Location: Charmouth, Dorset, UK. Posts: 3,601	Re: 3 valve 1920s set A very nice set in 'original' condition, I wouldn't be surprised if it still works, there were lots of sets like that about when I was a kid but not many left, especially in that condition. Peter

9th May 2012, 7:57 pm	#6
Boom Retired Dormant Member Join Date: Jan 2007 Location: Westbury, Wiltshire, UK. Posts: 2,451	Re: 3 valve 1920s set The grid leak was indeed o/c on mine but you can open them up and pop a small modern resistor inside. Beware the markings tough (though). Mine were not the same as modern components. What I read as 3 Ohm was actually 3 MEGohm!

9th May 2012, 8:03 pm	#7
AC/HL Dekatron Join Date: Nov 2003 Location: Heckmondwike, West Yorkshire, UK. Posts: 9,642	Re: 3 valve 1920s set It's a 1927 Cossor Melody Maker, the first of a long line of radios. They were sold as a kit, but the cabinet was made by various manufacturers. It was a three triode design, but a SG add-on unit was available. Later, a modification was released to convert the 1927 MM to screen grid. Yours is the original with the large tuning coil. PS Dust is always a good sign! Attached Thumbnails Last edited by AC/HL; 9th May 2012 at 8:04 pm. Reason: PS

15th May 2012, 5:37 pm	#13
Colin-M5FRA Retired Dormant Member Join Date: Jan 2011 Location: Sheffield Posts: 9	Re: 3 valve 1920s set Thanks the diagrams certainly helped. I did some checks today and the secondary of the transformer is open circuit. It's a Ferranti AF3. What are the chances of getting a replacement? Colin

17th Apr 2015, 10:58 am	#14
Jim McLay Tetrode Join Date: Feb 2010 Location: Sycamore House, Shankill, Dublin D18, Ireland Posts: 97	Re: 3 valve 1920s set Hi Colin, Did you end up finishing this set restoration? That transformer could be rewound although it's probably got thousands of turns of fine wire. I found an article in Practical Wireless May 1980 where Robert Thorton reported getting reasonable results using a small 20-0-20 V mains transformer as an intervalve transformer giving a step-up ratio of about 1:6. This is what I'm trying out in a TRF (you can see the thread so far on https://www.vintage-radio.net/forum/...php?p=745268)- I'm always hoping to finish making the parts! __________________ This retirement thing is worse than it was cracked up to be!