AUDIO OUTPUT TRANSFORMER PROJECT, SAVE ME! - VACUUM TUBE RADIO REPAIR - PART 2 Emerson 641B [4K]

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or "How I Learned to Stop Worrying and Love Rebuilding Transformers"
(with rusty junk, improper tools and loads of time...)
In Part 1 (see playlist below), we did the troubleshooting on this radio.
• Emerson 641B
It turned out that it had a blown audio output transformer. So, that's why they gave up! You know, because they cannot be fixed...right? Certainly not without special tools and training and a large amount of skill, right?
In this Part 2, let's see what we can do with bits of junk and rusty old tools and a boatload of time... can we save it? Without buying proper tools and careful precision? Let's just give it a try and run-through and see what is involved - will it even work??
BTW, I spent 10-12 hours (!) on this (not including editing out many hours of video).
See the checklist which appears, when status changes, for tracking what is discovered that needs addressing in Red, followed by Green when resolved.
Someday I may electrically restore this radio, if so, the playlist will link the restoration video with these resurrection videos. Turn on notifications to see if that video ever gets done.
This is not instruction, it is for entertainment for people like me who enjoy watching projects and the experiences gained. If you attempt to do some of the things in this video you are at your own risk. I am using special tech-bench safety equipment not detailed here so don't take for granted you can just plug these old items in safely without them being checked and repaired correctly. Check out the link below to Mr Carlson's Lab video below.
Vintage equipment used along the way:
Emerson Model 641B vacuum tube radio ca 1952
Heathkit Model IG-72 vacuum tube Audio Generator ca 1962
Acknowledgments and References:
[note: am in no way representing how these folks have shown doing this - I don't even think they would approve. I just took some bits of information and a lot of inspiration, and just gave it a shot with minimal tools and concern for precision, just to give it a try.]
Excellent, very clear and helpful discussion and demonstration of transformer measurement and characterization by Uncle Doug:
• Output Transformers: A...
‪@UncleDoug‬
Excellent videos on re-winding transformers by RestoreOldRadios, search his channel for many examples:
/ restoreoldradios
‪@RestoreOldRadios‬
Excellent video showing winding a transformer core by Delatsch:
• Practical Transformer ...
‪@Delatsch‬
Special thanks to Doug at DERB for the shout-out here:
• Something Different - ...
‪@DERB_Seymour_Indiana‬
Awesome discussion of bench safety including variacs and isolation transformers by Mr Carlson's Lab (highly recommended):
• Tech Tips Tuesday, Iso...
‪@MrCarlsonsLab‬
Modification method for a commercial Tripp Lite isolation transformer for tech-bench use by Todd Harrison, his channel is called ToddFun:
• ToddFun.com: Isolation...
‪@ToddFun‬
Thanks to shango066 for championing the approach of "fix it first", before mass re-capping. Had the person who attempted this repair used that approach, they would have had a much better result. See shango066 for many examples of that approach.
‪@shango066‬
Camera: Canon G7X Mark III
Mic: Rode Micro
Video Editing Software: Power Director
Video Editor: just me

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Опубликовано:

19 июл 2022

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Комментарии : 41

@anandawijesinghe6298 5 месяцев назад

I have done this myself; very satisfying to watch you do it instead of me! Great job ! Deserve $1000! 🥰

@PracticallyFixed 5 месяцев назад

Glad you enjoyed it!

@td7456 2 года назад

What's that old saying? "Ya never know, until ya try!" Congrats, great job on the rewind! I worked at a place that made deflection units for X-Ray equipment & other miscellaneous transformers! Believe me, I've seen much worse winding jobs from some of the engineer's prototypes! LOL

@PracticallyFixed 2 года назад

Thanks Tim! LOL

@OIE82 Год назад

I echo everyone else, sheer determination and experience (not necessarily with the project at hand) can spell success. Well done. Yea, you might have $2000 in labor but the satisfaction, in the end, is worth so much more. I have to say you have proven that you are qualified to fix dang near anything with almost nothing!

@fibberscloset498 2 года назад

The fishing reel is genius.

@PracticallyFixed 2 года назад

Thanks!

@jimnewman5596 2 года назад

That was an impressive repair for sure, I have never had an open audio transformer winding yet but you have given me the inspiration to give it a shot when the time comes.

@PracticallyFixed 2 года назад

Thanks, Jim! Yeah I guess you don't really need a lot of special equipment right? If the length of wire is the same you don't even need a counter apparently. Thanks again.

@RestoreOldRadios 2 года назад

Very cool. I’m still watching the rewind and will edit afterwards. Your patience, determination, creativity and skills made for a positive outcome. Well done and congratulations! Best, Don

@PracticallyFixed 2 года назад

Thanks Don, your many videos on transformers helped inspire me to give it a try. Left you a thanks at the end and in the description. Thanks a lot.

@chrisclark6192 2 года назад

Hi from the uk. I'm new to your channel. Your dedication and patience is very impressive and your skills have to be admired. A very good result and I enjoyed watching. I have also subscribed to your excellent channel, and will be catching up on all of your videos. Thoroughly enjoyed watching. Cheers Chris

@PracticallyFixed 2 года назад

Hello Chris - thank you so much for your kind words! It really made my day. Thanks again!

@dave1135 Год назад

David Tipton in new Zealand did a power transformer, quite a bit bigger, and he had a motorized winder/ counter and he made a tracking mechanism out of a old printer and a raspberry pi to run it to get tight even wraps.

@PracticallyFixed Год назад

Thanks Dave, just went and watched that. Really interesting. Thanks for the comment.

@terryblackman6217 2 года назад

Very very well done. It has prompted me to have a go at repairing an Ever ready portable I have with the same fault. Nice one.

@PracticallyFixed 2 года назад

Thanks! I did not have anything to lose except just some time. What a happy ending. Good luck with your's! Let us know here how it turns out - good luck! Thanks again for the comment.

@terryblackman6217 2 года назад

@@PracticallyFixed Will do. 👍

@chuck0mx 2 года назад

Yea... excellent work... It's a fascinating hobby... Congrats

@PracticallyFixed 2 года назад

Thank you very much!

@ericklassen742 6 месяцев назад

Kudos man! SUGGESTION FROM AN EXPERIENCED GUY BUT NOT TO STEAL YOUR THUNDER, an easy way for NEXT time is: size the wire by its gauge, dtermine its origunal length, weigh it and get a close estimate of how much wire you are replacing... (never mind the number of turns). Pull the old wire and save it in a ball to be weighed. Now wind new wire by wieght onto the core. Dress and solder the bew wires. YER DUN!

@PracticallyFixed 6 месяцев назад

Was hoping to not have to unwind all the way to find the break. But, then I was committed. Liked reusing the original wire however.

@josepheccles9341 2 года назад

It stands to reason the break is in the bottom layer. The heat in the saturated core is higher there.

@PracticallyFixed 2 года назад

Thanks for the note. I was hopeful because for the 1937 radio (Grunow 588) I did, the break was right at the top, so I guess that one was the stroke of good luck. This one unfortunately, as you say, is probably what we should expect. Thanks again.

@michaelclutton8446 9 месяцев назад

Great job, I thought it was excellent doing that with basic tools. The fishing reel was a great idea

@PracticallyFixed 9 месяцев назад

Thanks 👍

@sambillingsley6379 Год назад

You are the man!

@PracticallyFixed Год назад

Thanks, Sam!

@alainblazit9504 2 года назад

A faster way to know the turn ratio of a bad output transformer is to start from the recommanded load impedance of the output tetrode and the impedance of the loudspeaker. The turn ratio is the square root of the impedance ratio. Winding transformers is a long process. I wound some when I was young, but never with so thin wire. I used cardboard un the edges of the windings to protect and insulate it.

@PracticallyFixed 2 года назад

Hello Alain, you are absolutely right about the calculation. I did that with the text where we calculated the desired turns ratio when I checked the transformer after rewinding it. I was wondering if rewinding it as I had would still get the correct turns ratio. In hindsight I guess there was nothing to worry about since I didn't change the length of wire, but still, I didn't have a counter, etc. It was gratifying to see the ratio turned out to be the desired 25:1, which, as you said, we could calculate. I was very skeptical that I could handle that very thin wire that was 70 years old without it either continuously breaking, or the enamel coating breaking off. So I was so happy how it turned out. Thanks for the advise on the cardboard, next time I will do something similar. Thanks for the comment.

@jamesmdeluca Год назад

Greetings: Use your Variac to control the drill-motor speed (override built-in speed control by having trigger held full-on). OR if drill motor trigger lock permits fixed speed reduction. then set speed for fastest you expect to use and use Variac to reduce speed as needed. If you have an optical tachometer for car RPM, determine speed you will use in RPM, then calculate how long it will take to spool that length. (Every digital watch has a stop watch function.)

@PracticallyFixed Год назад

Hello James. That is a good idea, thanks. In this case I was really concerned about breaking the 70 year old wire as I was reusing it. Next time I may try it. Thanks again.

@hoosiernick Год назад

Fascinating, but a magnifying glass would have been very helpful,

@DERB_Seymour_Indiana 2 года назад

By Jove I think you've done it! Congrats. You have far more patience than I ever would have for such tedious work. Nice idea using that fishing reel for part of the effort. I've often wanted one of those coil winders, but I'm just not sure I would ever be able to git er done like you did. LOL

@PracticallyFixed 2 года назад

Thanks - I was really surprised it worked! If I had known it would have taken that long I probably would not have tried it. But it was just one more step, and another step, and the frog boiled in water haha. Hope you noticed I put in a thanks at the end of the video and also in the notes. Cheers

@DERB_Seymour_Indiana 2 года назад

@@PracticallyFixed Caught the notice at the end of the video, but admittedly I didn't see the mention in the description. You are very welcome and I do hoped it helped in some small way. :)

@PracticallyFixed 2 года назад

@@DERB_Seymour_Indiana Hey Doug, sorry you missed it. It is in the References and Acknowledgements Section near the end. Thank you!

@DERB_Seymour_Indiana 2 года назад

@@PracticallyFixed 👍👍

@waterfuel 2 года назад

My hand wound isolation transformer does not pass enough power. Does it need a resonant capacitor in series with primary to match the 20khz AC input? I even tried impedance matching that did not work either.