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 Post subject: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Sun 02, 2020 10:00 pm 
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Posts: 268
I have an audio output transformer and a filter choke with old brittle wire hookups.

Are there any tricks to saving these wires?
If not can they be replaced?

The only thoughts that come to mind are:
1) Put heat shrink over the existing old crusty wire casings.
2) Strip the old casing to bare wire and then put heat shrink over those wires to create a new flexible casing.

Or, if possible, tear apart the choke / output transformer and somehow splice in new wire to the windings?

Thank you,


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 12:42 am 
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Location: New Hampshire, USA
If the leads are stranded wire then they will be connected inside the casing but some of the connections may not be accessible. If you are really careful you can cut the connections and splice new wires, keeping the connections inside the casing so they’re not visible. Use small Western Union splices, then heat shrink to avoid future failure. You should be able to find cloth covered wire from some of the parts supply houses.

I would avoid heat shrinking over the entire length of the leads. After it’s cooled, heat shrink may make the leads stiff and hard to work with.


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 1:02 am 
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I would try to avoid opening them up, and rather, strip the leads to bare wire and use spaghetti for insulation.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 2:36 am 
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fifties wrote:
I would try to avoid opening them up, and rather, strip the leads to bare wire and use spaghetti for insulation.


Where the heck can you find plain old spaghetti these days? Not the superexpensive kind, varnished cambric or whatever, just the kind we used to use in great quantities in the '50s and '60s? I have a little bit left but not much, and I never see it advertised anywhere.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 2:44 am 
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Avery wrote:
fifties wrote:
I would try to avoid opening them up, and rather, strip the leads to bare wire and use spaghetti for insulation.


Where the heck can you find plain old spaghetti these days? Not the superexpensive kind, varnished cambric or whatever, just the kind we used to use in great quantities in the '50s and '60s? I have a little bit left but not much, and I never see it advertised anywhere.


Just Radios has it. I make sure I get some more every time I order.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 2:45 am 
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Saw a video on the utube a while back where a guy coated everything with liquid tape. Worked like a champ...

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 3:00 am 
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Avery wrote:
fifties wrote:
I would try to avoid opening them up, and rather, strip the leads to bare wire and use spaghetti for insulation.


Where the heck can you find plain old spaghetti these days? Not the superexpensive kind, varnished cambric or whatever, just the kind we used to use in great quantities in the '50s and '60s? I have a little bit left but not much, and I never see it advertised anywhere.


Sal has it too - in colors! =================>>>>>>>>>>

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 3:10 am 
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The main problem is that the insulation is probably just as bad inside the metal housing. So whatever you do outside won't decrease the possibility of a short inside. For a real, permanent, fix, you have to take it apart and do your repair in a way that prevents shorts to the case or core. I would just replace the wire.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 5:19 am 
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Avery wrote:
fifties wrote:
I would try to avoid opening them up, and rather, strip the leads to bare wire and use spaghetti for insulation.


Where the heck can you find plain old spaghetti these days? Not the superexpensive kind, varnished cambric or whatever, just the kind we used to use in great quantities in the '50s and '60s? I have a little bit left but not much, and I never see it advertised anywhere.

When I posted that, I was thinking back to when I bought some at All Electronics. In looking at their online catalog however, it's not what we used to use, but rather "heatshrink tubing". Of course it can be used for insulating bare wire, and simply not heating it to shrink, which is the way I use it;
https://www.allelectronics.com/category ... ing/1.html

Sal is now apparently selling spaghetti by wire gauge, whereas All sells heatshrink by measured diameter.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 7:33 am 
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Hello guys,
mouser sells the sleaving too


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 1:05 pm 
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Location: Potomac, MD 20854
Thanks for the spaghetti tips! Sorry for the off-topic query.

fyi, the Just Radios product is heatshrink tubing, not the old stuff I was referencing. But thanks to Fifties for pointing out something so obvious I never thought of it--heatshrink can be used just like old-fashioned spaghetti. Just don't shrink it. (slap of hand to forehead)

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 2:52 pm 
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Thank you for everyone's tips and thoughts!

Applying a variety of the thoughts offered would the following be the proper actions to repair?

1) Strip the leads to bare wire.

2) Coat the base of the leads that make contact with the metal casing with Liquid Tape.

3) Cover the those liquid taped wire areas at the base of the metal casing with about an inch of heat shrink pushed in as far as possible to the windings then apply heat from a heat gun to complete the bond.

4) Cover the entire wire with spaghetti along with the new base coating.

5) Apply some Liquid Tape at the far ends to hold the spaghetti in place leaving about 1/2" of exposed wire for its reconnection to the proper component.


Side notes:
The wires are stranded not solid.

Confirm:
Taking apart and installing new wire is not recommended?

Best,

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 5:09 pm 
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Okay, curiosity got the better of me and I opened it up and no I don't think I want to attempt to redo these wires.

So spaghetti it is.

But if one really wanted to replace the new wires how would you go about it?


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 5:28 pm 
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Scott Madison wrote:
If the leads are stranded wire then they will be connected inside the casing but some of the connections may not be accessible. If you are really careful you can cut the connections and splice new wires, keeping the connections inside the casing so they’re not visible. Use small Western Union splices, then heat shrink to avoid future failure. You should be able to find cloth covered wire from some of the parts supply houses.

I would avoid heat shrinking over the entire length of the leads. After it’s cooled, heat shrink may make the leads stiff and hard to work with.



Scott already answered with a Western Union Splice and heat shrink.

Thank you all!

I have the knowledge to fix the wires because of you all.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 5:52 pm 
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Hello guys,
I use that splice all the time and here is the proper way to make it


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Mon 03, 2020 8:12 pm 
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Location: Thornhill, Ontario, Canada
Over the years, I have done these things on both vintage OPTs and PTs (methods not ranked, depends on damage found):
1. Add a small amount of flexible glue, e.g. ShoeGlue, to cracked original wire insulation and down just a bit into the bobbin; slide short length of sleeving (spaghetti) over it, pushing it down carefully into the bobbin. I use the flexible, compressible, black, fabric-like stuff as I have a lot of it, but it does tend to fray... you can alleviate this a bit by a light smear of glue on the outside at the end (let it set a bit before use.)
2. ditto, but finish with heat-shrink (apply heat all around carefully!)
3. "J-hook (plus solder)", carefully, a new wire close to the bobbin, finish with spaghetti or heat shrink, as above. I recently salvaged a Hammond 125C OPT P-P primary like this (spaghetti and glue.)
When reassembling the end shells, the spaghetti or heat shrink may be outside of the opening, generally a good thing to protect the wires as better than the original insulation.
Of course, if you do the Western-Union splice, insulate as above.
My known failures to date: nil!
Hope this helps.
Cheers,
Roger

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Last edited by engineer on Aug Tue 04, 2020 5:11 am, edited 1 time in total.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Tue 04, 2020 3:18 am 
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Since the wires are well separated where the come out of the winding, putting new insulation over the old wires is entirely practical. Two things to watch out for: make sure the new insulation goes all the way to the paper wrap and be sure you know which wire is which when you are done; new insulation isn't likely to preserve the original color code.

As for replacing the wire, the way I have done it is to slit the outer layer of paper near one end and fold it back. Then slit the next layer at the opposite end and fold it back. Keep working on opposite ends until you reach the wire from the winding. CAUTION, the wire is likely to be thin and fragile. Unsolder the old lead and splice the new lead to the magnet wire. Insulate it as needed (the paper wrapping may have been designed to do this), fold the paper back and tape it in place layer by layer.

It doesn't look like you have to go to such extremes with your unit but sometimes it's the only way (like Heathkit stereo output transformers where shorts occur inside the paper wrapping).

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Tue 04, 2020 7:07 pm 
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Avery wrote:
Thanks for the spaghetti tips! Sorry for the off-topic query.

fyi, the Just Radios product is heatshrink tubing, not the old stuff I was referencing. But thanks to Fifties for pointing out something so obvious I never thought of it--heatshrink can be used just like old-fashioned spaghetti. Just don't shrink it. (slap of hand to forehead)


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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Wed 05, 2020 1:22 am 
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SX-42 wrote:
But if one really wanted to replace the new wires how would you go about it?

Peel back the paper wrapping until the solder joint to the transformer winding is exposed.

Unsolder old wire, attach new wire using a small Western Union splice, solder splice.

Then re-tape with gummed Kraft paper tape.

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 Post subject: Re: How To Save Old, Brittle, Output Transformer Wires?
PostPosted: Aug Thu 06, 2020 1:41 am 
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The transformers I have done used a pigtail splice to the lead wire; a Western Union splice is too long.

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