Author Topic: Coil repair  (Read 156 times)

Mrbill5

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Coil repair
« on: June 30, 2020, 11:35:11 AM »
This is one of my least favorite repair jobs.  Just got 2 clocks in to be made both safe and functional.  One had the terminals ripped off the coil, no connected wiring at all.  The other had wiring still connected but the coil terminals were loose.  Sure enough when I tried to unsolder the power cord both coil terminals came off.
I have a small stash of extra coils and really do not like using them up unless there is no choice.  Dissection of both coils showed the wiring ends were still there and I got a good multimeter reading of about 700 ohms.
So first thing I did was remove as much loose paper insulation as possible to end up with a solid  area where I could glue my own terminals. For each coil  I cut 2 pieces of 1/32" copper sheet into 2 strips.  Bent them to a 90 degree angle and glued them to the coil.  Next I carefully removing the wire insulation with a scalpel.  The wires were soldered in place, continuity was checked, then glass insulation tape and finally a coating of black liquid tape.  Would have nice to have holes in the copper ends, maybe next time.  I am sure my customer will be glad that his clock electrics are not only functional but a lot safer than when he sent his clocks
 to me.
And he was aware that the terminals were both loose and missing on his clocks. 
« Last Edit: June 30, 2020, 05:50:23 PM by Mrbill5 »

henny

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Re: Coil repair
« Reply #1 on: July 01, 2020, 11:31:23 AM »
Bill,
That looks great! Assuming you can locate both broken coil wires there's another option.

Forget the terminals and solder on a couple short pigtails of 18 AWG THHN stranded wire and insulate the splice. Then slip on a sleeve of 30mm double wall, adhesive lined heat shrink tubing with a 3:1 shrink ratio.  The 3:1 adhesive lined heat shrink will constrict the splice very tightly to the coil's core. And since it's double wall, it'll be very strong and durable. (unlike the smaller single wall stuff).   Then attach the cord with small twist on wire nuts, etc.

It'll make these old coils better then new.

https://www.ebay.com/itm/DW1S3X-30-0-Dual-Wall-3-1-Heat-Shrink-Tubing-30mm-1-25-Black-1-Foot-Qty-5/142920151135?hash=item2146b4705f:g:FooAAOSw~U5a~DHy


Mrbill5

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Re: Coil repair
« Reply #2 on: July 01, 2020, 03:39:27 PM »
Henny
I lucked out with the wire ends still there.  I like your idea of pigtails.  I see an issue tho of not a whole lot of room in most of the cases for wire nut connections and the movement and the mounting hardware.  It would work in some clocks that have the room like a Brandon.
Or never get another clock with a coil to repair.    D%D
If only.

Placed an order for the shrink tubing.  Will play with it with some"donor" coils that I just cannot seem to throw out.
« Last Edit: July 02, 2020, 02:52:10 PM by Mrbill5 »

Mrbill5

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Re: Coil repair
« Reply #3 on: July 01, 2020, 04:44:55 PM »
Discovered a deficency in my design.  When soldering on the wires to the copper terminals the glue softens.  The glue seems to reharden and is also held with the glass tape.  A correction would be to make the copper glue spots 2 to 3 times longer just like the original Telechron terminals. 

I got the clock all buttoned up, soft glue joints and all.  Ran the clock for 12 hours so everything should be at normal temps.  Unplugged the clock, opened it up.  The terminals are SOLID again.  Very glad. 
« Last Edit: July 02, 2020, 10:06:52 AM by Mrbill5 »

max9090

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Re: Coil repair
« Reply #4 on: July 01, 2020, 11:22:50 PM »
Hey Bill - what glue did you use to glue the new terminals to the coil?

Mrbill5

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Re: Coil repair
« Reply #5 on: July 02, 2020, 05:36:54 AM »
E6000.

When I do this again I will make the contact area about 3mm wide x 8mm or even longer.
« Last Edit: July 02, 2020, 10:07:44 AM by Mrbill5 »

max9090

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Re: Coil repair
« Reply #6 on: July 02, 2020, 12:37:19 PM »
Thanks. Something tells me I'm going to find myself in this situation eventually. Thanks to your posts I'll know how to deal with it.

Mrbill5

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Re: Coil repair
« Reply #7 on: July 03, 2020, 11:59:11 AM »
My next challenge just arrived.  Coil repair #3 this week.  The wires are still good, 700 ohm resistance.  Think I might try thr Henny repair method when I get the shrink tubing.

henny

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Re: Coil repair
« Reply #8 on: July 04, 2020, 05:25:31 PM »
I think it's actually more compact because the coils leads are thin flexible 18 AWG wire vs. solder terminals and thick old cord.  You can make the connection any way you want. (wire nuts, butt crimps, solder splice, terminals, etc.).  Solder terminals held on by paper was not one of Telechron's better ideas.


Mrbill5

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Re: Coil repair
« Reply #9 on: July 04, 2020, 05:34:16 PM »
Very nice.  I have a coil in need of fixin and shrink tube coming in the mail.  Will try your design.  Funny how we are reverting back to the B rotor/coil design with the leads

And thanks for the info on the low temp solder.  I used it this morning to fix a cracked alarm set gear.  Took a lot less heat than normally needed with Sn-Pd solder.

Mrbill5

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Re: Coil repair
« Reply #10 on: July 06, 2020, 04:14:11 PM »
Got the shrink tubing.  Found a coil that needs fixing. Used glass tape to insulate the wire to wire solder joints and hold the 18ga wires to the coil.  Then added the shrink tubing.

henny

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Re: Coil repair
« Reply #11 on: July 06, 2020, 05:33:32 PM »
Got the shrink tubing.  Found a coil that needs fixing. Used glass tape to insulate the wire to wire solder joints and hold the 18ga wires to the coil.  Then added the shrink tubing.

Bill,
That coil should last a few hundred years and be safe!!

Mrbill5

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Re: Coil repair
« Reply #12 on: July 08, 2020, 02:45:20 PM »
Just got a parts clock and found that the coil had a loose terminal.  After removing the brittle outer paper I found that the one terminal was loose and the other terminal and base paper were loose.  Glued down the paper and both terminals with e6000.  Then glass insulation tape over the whole and liquid tape.  Should be good for another 50 years.
AND, my original copper contacts designs were undersized.  Should have been at least 3/8" long in the adhesion areas.  Warren had a good design, just adhesion and insulation products of the day were what they were.

 

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