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Philco 76 output transformer #2848 - Printable Version

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Philco 76 output transformer #2848 - Stan the Man - 12-10-2020

So I have the field coil done(my first), But I also have an open side in my output transformer. Since I have not been able to find a suitable replacement, I am thinking I will attempt to rewind. I am NOT up on transformers. After watching and reading everything I can find, I came up with this conclusion. This transformer has an 80:1 ratio. 80 turns on the primary to every 1 turn of the secondary. Now if I copy that, as best I can, will that work?


Stan

RE: Philco 76 output transformer #2848 - Radioroslyn - 12-10-2020

You may want to have a look at this: https://philcoradio.com/phorum/showthread.php?tid=17572 around post 12/13 or so. Most of it's abt the input transformer but the mechanics of it is the same. Take it apart, count the turns and layers rewind accordingly.

RE: Philco 76 output transformer #2848 - Stan the Man - 12-10-2020

Thank you for the link, and the reply. I unwound the primary yesterday. It was not pretty. The transformer was impregnated with a waxy substance, and there were spots of corrosion all over. As soon as I would get it started unwinding, it would break. It became impossible to count turns. And by that time I was so aggravated, I forgot what layer I was on. Now I have a clean-er core, and a nice secondary winding. All I need is the primary.


Stan

RE: Philco 76 output transformer #2848 - David - 12-10-2020

You know the wire size might take all the pieces of the pri. wire and measure the total length add enough for few extra turns and give it a try. Much easier to remove a turn than add a turn. Gook luck David

RE: Philco 76 output transformer #2848 - Stan the Man - 12-10-2020

David,. I'm gonna say the wire is 38ga. As for measuring the length, I would say thats not possible now. I can still see the imprint of the wire on the core. So I know how wide the layers will be. I can easily count the secondary wire turns. So I should be able to come up with something close. I just wanted to know if I was on the right track.

Stan

RE: Philco 76 output transformer #2848 - David - 12-10-2020

I have not looked but is there a spec on the resistance of the primary if so then look up the resistance per 100 feet of 38 ga or something like that an   guess at the length add a little extra. Stay Safe David

RE: Philco 76 output transformer #2848 - morzh - 12-10-2020

Stan, get a Core!

Icon_lol

RE: Philco 76 output transformer #2848 - Stan the Man - 12-11-2020

I don't seem to be able to find a spec for the transformer, other than its 80:1 ratio.
My core is still very much intact, with the secondary still in it. I have ordered wire, and I have a cheap coil winder, so we will see what happens.



Stan

RE: Philco 76 output transformer #2848 - Phlogiston - 12-11-2020

Re-stuffing your power transformer:

https://www.russoldradios.com/blog/back-on-the-farm-radio

RE: Philco 76 output transformer #2848 - Radioroslyn - 12-11-2020

Ed sez: I'm now finishing up the O/P transformer. Primary is done (#35 wire, 20 layers of 140 turns each with center tap). The secondary will be next. That is 18 AWG - incredibly beefy considering the voice coil of the speaker!

This = a primary of 5.2k load for the p/p 42's in a triode reconfiguration (Ed's 16X). Your 45's require a bit of a lower load abt 3.2k so a little less wire/turns. [Image: https://philcoradio.com/phorum/images/smilies/icon_smile.gif]

RE: Philco 76 output transformer #2848 - Arran - 12-11-2020

I was going to suggest cleaning up the old wire from the wire from the primary, removing the wax, and weighing it. That's an alternative method to measuring the length if you can figure out how much a foot of a given gauge of wire weighs, though it is not easy without something like a chemist's scale.
Regards
Arran

RE: Philco 76 output transformer #2848 - Stan the Man - 12-12-2020

Arran, The thought did occur to me. For reference sake. Whatever is on that wire was all over my hands by the time I was finished. What a sticky mess. If I thought I would be able to clean the wire and get a good weight that might be worth a shot.


Stan

RE: Philco 76 output transformer #2848 - Phlogiston - 12-12-2020

A person generally does not have to worry about getting too much wire on the form unless they use much smaller wire. If laid down neatly in layers, there is generally enough space. If bulk wound or wrapped with anything thicker than stock - no way.

RE: Philco 76 output transformer #2848 - Stan the Man - 01-02-2021

NOT fun.
                   

RE: Philco 76 output transformer #2848 - Stan the Man - 01-12-2021

Have to get it all back in the can.