Transformer Ratio Analyser - UK Vintage Radio Repair and Restoration Discussion Forum

David G4EBT · 2nd Jan 2016, 7:10 pm

In tidying up a heap of papers of circuits and home-brew projects that I've accumulated, I came across a simple transformer ratio analyser which featured in Nov 1974 Radio & Electronics Constructor. I can't say I've ever felt a pressing need to have such an instrument, but that said, I do have quite a lot of audio transformers about which I know little, especially transistor ones with no markings on them, and some 1930s inter-valve transformers.

In looking at the circuit, it dawned on me that I had all almost all of the bits to hand to make one.

Although the author states that due to the limitations of this simple instrument it doesn't warrant the expense of a permanently installed 50uA meter, I had one to hand anyway so I built it in. The only part I didn’t have was the 10K wirewound pot, which I bought new off e-bay from Hong Kong, for the ludicrous price of £2.40 post free. I designed a little turret-board layout so that it doesn't look too much of a 'rat's nest'. I made a comb-jointed box from scrap mahogany, and designed a front panel, which I calibrated per the instructions when the pot was installed. The front panel consists of 2mm 'Paxolin', overlaid with lettering on card, which is encapsulated, then it has a piece of 2mm clear acrylic over it to protect it.

The circuit shows a 91 Ohm resistor for R2, as being near enough (+1.1%) to the 90 Ohm, really called for, but to be pedantic, I used a 68 Ohm and 22 Ohm in series to achieve 90 Ohms. (Shown on the turret board as R2a and R2b). I used a 'figure of 8' mains socket for the mains lead input - I didn't bother to add a fuse, except in the mains plug.

I've finished this little project and it seems to work well. I've just tested a couple of vintage inter-valve transformers, which have registered a null at 3:1 and 4:1, which sounds sensible. The circuit and turret-board that I designed are attached, and in another post I’ll add some pics of the finished tester. It will only very occasionally be used - just a bit of fun really, to satisfy my compulsion to build yet another little home-brew test-gear gizmo which will probably find little use in my workshop!

The 3-page article from Nov 1974 Radio & Electronics Constructor Magazine can be downloaded from the link below - seventh one down the list:

http://www.vintageradio.me.uk/radconnav/misc.circuits/

Not much else to say about it, other than I hope it's of interest.

David G4EBT · 2nd Jan 2016, 7:15 pm

A few pics of the finished analyser attached.

A few less bits in my 'spares box', and one more gizmo to stick on a shelf.

As they say around these parts: 'summat from now't'!

timewave · 2nd Jan 2016, 7:39 pm

I read the same article about 6 weeks ago and collected the components together from my stock but became side tracked by other projects.

As usual you have set a very high standard, one which most of us will never attain.

John G4IJD

2nd Jan 2016, 7:56 pm

Article jpgs unreadable (yet again on this forum) please can the mods (well Paul S) make the maximum jpg size a bit (twice?) bigger. Nothing to do with Davids scanning.

Nice simple and useful project.

Sean Williams · 2nd Jan 2016, 8:06 pm

Open them with a proper photo viewer package, and use zoom - works well enough to make sensible size (and free) jpegs readable...

Thanks for posting this David, yet another useful gadget that I wont have yime to build!

Nickthedentist · 2nd Jan 2016, 8:12 pm

Quote:

Originally Posted by Sean Williams

Open them with a proper photo viewer package, and use zoom - works well enough to make sensible size (and free) jpegs readable...

I've just tried, and maybe my eyes are tired, but it was heavy-going.

PDFs seem to be the solution, if David has the software to produce them.

I would echo Sean's sentiments about David's projects. I wish I had more time. Maybe one day

N.

David G4EBT · 2nd Jan 2016, 8:18 pm

Thanks for the kind comments everyone.

As to the illegibility of article attachment, if you go to the link that I provided above, the article will print off A4 size, or will be perfectly legible to read:

http://www.vintageradio.me.uk/radconnav/misc.circuits/

Hope that helps.

2nd Jan 2016, 10:07 pm

Yes, they are readable, probably the minimum you can get away with for comfort. Now the rest of the night has been hijacked looking through all of those. Ironic thanks!

2nd Jan 2016, 7:10 pm	#1
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,760	Transformer Ratio Analyser In tidying up a heap of papers of circuits and home-brew projects that I've accumulated, I came across a simple transformer ratio analyser which featured in Nov 1974 Radio & Electronics Constructor. I can't say I've ever felt a pressing need to have such an instrument, but that said, I do have quite a lot of audio transformers about which I know little, especially transistor ones with no markings on them, and some 1930s inter-valve transformers. In looking at the circuit, it dawned on me that I had all almost all of the bits to hand to make one. Although the author states that due to the limitations of this simple instrument it doesn't warrant the expense of a permanently installed 50uA meter, I had one to hand anyway so I built it in. The only part I didn’t have was the 10K wirewound pot, which I bought new off e-bay from Hong Kong, for the ludicrous price of £2.40 post free. I designed a little turret-board layout so that it doesn't look too much of a 'rat's nest'. I made a comb-jointed box from scrap mahogany, and designed a front panel, which I calibrated per the instructions when the pot was installed. The front panel consists of 2mm 'Paxolin', overlaid with lettering on card, which is encapsulated, then it has a piece of 2mm clear acrylic over it to protect it. The circuit shows a 91 Ohm resistor for R2, as being near enough (+1.1%) to the 90 Ohm, really called for, but to be pedantic, I used a 68 Ohm and 22 Ohm in series to achieve 90 Ohms. (Shown on the turret board as R2a and R2b). I used a 'figure of 8' mains socket for the mains lead input - I didn't bother to add a fuse, except in the mains plug. I've finished this little project and it seems to work well. I've just tested a couple of vintage inter-valve transformers, which have registered a null at 3:1 and 4:1, which sounds sensible. The circuit and turret-board that I designed are attached, and in another post I’ll add some pics of the finished tester. It will only very occasionally be used - just a bit of fun really, to satisfy my compulsion to build yet another little home-brew test-gear gizmo which will probably find little use in my workshop! The 3-page article from Nov 1974 Radio & Electronics Constructor Magazine can be downloaded from the link below - seventh one down the list: http://www.vintageradio.me.uk/radconnav/misc.circuits/ Not much else to say about it, other than I hope it's of interest. Attached Thumbnails __________________ David. BVWS Member. G-QRP Club member 1339. Last edited by David G4EBT; 2nd Jan 2016 at 7:24 pm.

2nd Jan 2016, 7:15 pm	#2
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,760	Re: Transformer Ratio Analyser A few pics of the finished analyser attached. A few less bits in my 'spares box', and one more gizmo to stick on a shelf. As they say around these parts: 'summat from now't'! Attached Thumbnails __________________ David. BVWS Member. G-QRP Club member 1339.

2nd Jan 2016, 7:39 pm	#3
timewave Pentode Join Date: Apr 2006 Location: Clitheroe, Lancashire, UK. Posts: 173	Re: Transformer Ratio Analyser I read the same article about 6 weeks ago and collected the components together from my stock but became side tracked by other projects. As usual you have set a very high standard, one which most of us will never attain. John G4IJD __________________ Old radio engineers never die, they just go intermit...mit...mit...mit...

2nd Jan 2016, 7:56 pm	#4
Guest Guest Posts: n/a	Re: Transformer Ratio Analyser Article jpgs unreadable (yet again on this forum) please can the mods (well Paul S) make the maximum jpg size a bit (twice?) bigger. Nothing to do with Davids scanning. Nice simple and useful project.

2nd Jan 2016, 8:06 pm	#5
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,517	Re: Transformer Ratio Analyser Open them with a proper photo viewer package, and use zoom - works well enough to make sensible size (and free) jpegs readable... Thanks for posting this David, yet another useful gadget that I wont have yime to build! __________________ Engineers make things work and have spare bits when finished

2nd Jan 2016, 8:18 pm	#7
David G4EBT Dekatron Join Date: Feb 2003 Location: Cottingham, East Yorkshire, UK. Posts: 5,760	Re: Transformer Ratio Analyser Thanks for the kind comments everyone. As to the illegibility of article attachment, if you go to the link that I provided above, the article will print off A4 size, or will be perfectly legible to read: http://www.vintageradio.me.uk/radconnav/misc.circuits/ Hope that helps. __________________ David. BVWS Member. G-QRP Club member 1339.

2nd Jan 2016, 10:07 pm	#8
Guest Guest Posts: n/a	Re: Transformer Ratio Analyser Yes, they are readable, probably the minimum you can get away with for comfort. Now the rest of the night has been hijacked looking through all of those. Ironic thanks!