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Modifying Power Transformers - Sharing Old HAM Knowledge - And More Tips Too!

🕑 Added 2024-09-17 03:39:33 +0000 UTC

Comments

Michael in Florida

Great stuff. Thank you.

Mike Pelletier

I did this on a torroidal transformer for My Loftin-White amp, the 45s needed 2.3V, works great

David simpson

Good video. Thanks for the explanation.

Beaky Twitch

Your description assumes a rectifier tube with the heater being also the cathode. If the rectifier tube uses indirect heating, it may do so to make a delay so that HT is not generated until the other tubes are conducting. That protects against switch-on voltage surges. I am making some sort of HT load that will temporarily pull any voltage surge back into range, but otherwise do nothing once the other tubes are conducting.

David Daugherty

Great tip, thanks Paul. I feel like your my Elmer and I couldn't ask for more. Thank you a million times! Keep the videos coming!

Clinton Randolph

Great tips, Paul! Thanks loads!

Fred Flickinger

Very useful! Many thanks!

Alessandro Verona

Great video, the only place where I've found this kind of knowledge is in a book specific for designing tube amp power supplies, and still it wasn't this complete. I've just faced a transformer problem during some recent radio restorations: an old philips receiver had a autotransformer that looked like a regular transf with primary and secondary, it took a while to figure out how it was wired originally and still it didn't help much since it doesn't isolate galvanically from the wall. Similar problem with an old Ham transreciever where he used the secondary in a boost conf. to boost the voltage probably for the power valve, again no isolation from the wall was used and the chassy was live...

Randy Clarke

Thanks Paul, another great video of useful information. Keep them coming.

Shawn Wrona

Thanks for this! I did some experimentation yesterday with a few transformers, just to get a little experience with this trick. Had fun doing so!

Shawn Wrona

Thanks for that little bit of knowledge you passed there… something to keep under my hat. I’m still fairly new to electronics, but love to tinker.

Shawn Wrona

I have a few toroidals here.. I think I’ll do a bit of experimentation tomorrow

Ioan Koka

Not to mention you can tap into the widings, finding the voltage desired :)

Dale

Awesome and useful bits of knowledge that you explained so well, I think they'll remain stuck in my noggin. One idea that occurred to me that you didn't talk about is removing the paper on the transformer and unwinding some of the turns on the outer winding. I'd think this could be useful in a variety of ways. Not sure it would be practical if the transformer is varnish impregnated but maybe. I'm on a tight timeline remodel of our Victorian home but if I can sneak in a little time, I'll try and post the result. BTW it didn't even occur to me that I should worry about applying this to my old radios as I restore them. I'll now check the specs on them. That said, most have power transformers with end bells. Don't know what the windings inside look like. I suppose worse case we could mount a filament transformer under the chassis and use it's secondary to buck the primary of the main power transformer. You are an inspiration!

1 Stephen J

Mr. C, I dont know much but I have learned a lot so far and I never expect to put much of this knowledge to use. this lesson my take away is wireless transfer of electricity. Amazing. I shared the basics with my Son and he also was pretty amazed. His biggest retort was that no one know what electricity is! We have been able to work with it, but.... I looked on Wikipedia and found a lot of information, some I knew. But Mr. C. , what is it? Hopefully I am the only one in the dark and could everyone with the answer weigh in? Thanks, Steve

Steve Foudray

In guessing this works with toroidal transformers . Also curious about load/ noload voltages. A diode and a DC load for testing.

Jim Edmondson

These useful ‘hints & kinks’ deserve attached Forrest Mims style notes!

Kenny Fidler

This information is very helpful! Thank you!

David Pearce

BTW, This is the ONLY place I’ll allow the term “TRICK,” because it’s TRUE: You’re giving people a shortcut, a hack, on how to accomplish an important thing. • That’s far, FAR different than all the clickbait one sees today: • “Just try this ONE SIMPLE TRICK to empty your bowels each night, 😑!”

NeonHomer

Speaking of old ham stuff, I've got a Gonset Communicator II I bought at a hamfest to see if I could get it working. I've had it two years and haven't touched it...

Leonard Peters

Thanks, good information.

mitchellboomphi .

Absolutely amazing. To think of all the instances I could have done this instead of the hard way!

Don Bray

Thanks, Paul. Guess I'm showing my age...been doing this for a long time!

Sheldon Butler

Awesome video. What a great tip! My house voltage is about 125VAC so glad to learn the buck trick for my older 115-117V tube test equipment and radios I'm working on to extend their life.

Brian Wood

Thanks for the info, Paul. I have a HAKKO de-soldering gun from Japan that required 100v, but all I could find for a reasonable price was a 240 - 110v Transformer. Now I can use your buck trick to reduce this to 100v. Thanks for sharing.

Mr Carlson's Lab

That depends how, and where they placed the rectifier filament winding during the transformer manufacturing. Keep in mind, that filament winding has hundreds of DC volts on in while the radio is operating, so there is a good chance it's better isolated than the primary.

Brian

I'm guessing the buck trick in the second half of the video would significantly reduce the isolation rating of the transformer?

Mr Carlson's Lab

No, either direction is fine.

Mr Carlson's Lab

In many cases the resistors are not needed now. I have factory SS rectifiers for 872 replacements from the 70's with no parallel resistors as well. If you have enough diodes in series that the PIV would never be met, your usually good to go.

James C. Hall

Exactly what I did with my 516F-2 PS for a Collins KWM-2 to bring the PS down to 117VAC and keeping filament voltage 6.3v across the radio. Works great ! Using SS diodes instead of the hot rectifier tubes.

Clint Allsopp

Paul, Thank you as always! I wish I had known you 25+ years ago. Just finished reading a book on crystal radios and the author was constructing a coil and used the formula which sounds close to transformer coil counting: N = Square Root over (L x (18 x d + 40 x l divided by d squared). d - is the diameter of the coil form. l - is the length of the winding. L - is the Henry (ųH) design target. N - the number of turns you need. Would be neat to see if the formula works for the turns count or close to it.

Don Bray

Good tips, Paul. I'm wondering about differences in the leakage currents of the 1N4007s causing unequal sharing of the reverse voltage, which would of course reduce the total PIV rating. I've seen older supplies with high value equalizing resistors across the diodes. Or have modern devices gotten so good that it's no longer a concern?

Stuart Ambler

Thanks! I'd thought there might not be enough room to put something there, but since the video says it should be done at the end, maybe there would be. Possibly it could even reduce friction, depending.

Tom Harris

good tips. Another is if you have a set with multiple dial lamps, like #47, now you can but LED replacements, saving a ton of current draw from the 6 V winding. (.15A each )

David Kuhn

Damn, I never would have thought of that; wow; too cool (as the kids said 30 years ago - lol)

Donald J Arndt

Paul - Does it matter whether you wind CW or CCW?

Larry Merrill

Maybe one day you shows us how to rebuild transformer instead of buying a replacement esp. hard to find transformers

Kevin Martin

I was thinking that one should wrap a layer of paper around the outer legs of the core to avoid scraping the wire insulation. These could remain when done to help insulate the wire from the core.

Kenny Manchester

Ideas for all those transformers I've salvaged over the years are flowing! I need to sort out the current capacities of each along with voltages. A new DIY differential PS may finally fill a space on my bench! Very useful info and tips here Mr C!

Denis Renaud

A good insulating paper to use is "Fish Paper". Search Amazon and it will come up.

TWISTED1

More great knowledge! Thanks for sharing , your knowledge. I think back , amd say what kind of knowledge could have been shared for everyone if a platform like this was around in the 40s and 50s . Thanks Mr.C

Lou Lwin

For the tough older varnish, sometimes dipping the ends in meths and burning it off with a lighter is quite a good option, it then just crumbles away

Keri Szafir

Nice. EI cores can sometimes be taken apart making heavier winding modification a lot easier, but from my experience, when they're glued together by enamel or welded, there's no other way than painstakingly putting those wires through the gaps. Toroid transformers can be modded pretty easily as long as the middle hole is not filled with resin. If that's the case, you need to remove it first, risking damaging the outermost winding. I test the turns/voltage ratio by adding 10 turns to the transformer, loading it and measuring the voltage. Volts per 10 turns can be inverted and multiplied to get the turns per volt number. Measuring the idle voltage and basing our calculations on it will result in too low voltage when the transformer is in proper operating conditions. It's a good idea to use some sticky or insulated tape on the inner surface of the core to prevent damage to the magnet wire's enamel.

Lily Finley

If you wanted to keep using the directly heated rectifier tube, could you build a small low-voltage transformer, with e.g. 60:50 turns, to attach the rectifier's filament to the regular filament supply?

Jared Kusner

Thanks for an awesome class. I learned a lot today. I have an old keyer project and need a filament winding. Now I can add one with confidence.

Steve Brace

A couple of dumb questions: If you're winding around the primary and secondary, is there any effect on the secondary? For low current applications, can you wind around one side of the outer core? Forgive my ignorance, just sticking my neck out for ridicule :)

Mr Carlson's Lab

Yes, you just have to be careful. Not much of a choice in a situation like this.

Stuart Ambler

I would be wary of scraping off some insulation while winding, not knowing the resistance to scraping of the varnish on whatever wire I found, or the sharpness of the edges of the laminations of the core. Is this not a concern?

Mr Carlson's Lab

For a transformer that's not already wound tight to the core, yes I agree. In this case, wind where the gaps are.

Jeff Ankstitus

Former xfmr design engr....to measure the turns/volt or volts/turn I recommend 10 turns for the sense winding. More turns =greater accuracy. When winding new coil approximate total wire length and cut. Start winding in middle....one end thru each side. Less chance of scraping off enamel and shorter wire lengths.

Bjorn V

Love it, thanks for sharing these tricks. Grtz

Marshall Lewis

Keep it coming. My brain is ready!

Donald Kash

My Dad had many stories when he was in the signal corp in WW2. Licensed at 16, W9LDZ. He was 20y/o and had to rewind many transformers then. So, one might say this is “young” ham knowledge.

Mr Carlson's Lab

Thank You JH, I appreciate that!

Jason

Transformer knowledge is greatly appreciated! You are the best around, thank you Mr Carlson!!!

Mr Carlson's Lab

Thank You for your kind feedback Randy!

Randy McCauley

I so appreciate your teaching, you have been the absolute best I've ever experienced, thank you for your efforts, it doesn't go unappreciated and is shared with others.