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Coil rewinding




 
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Author Topic: Coil rewinding  (Read 1069 times)
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wa2pjp
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« on: December 10, 2017, 09:27:30 PM »

I have a bad IF coil in a Hallicrafters receiver that I am restoring, does anyone know of somebody that does IF coil rewinding?

Thanks
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Detroit47
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« Reply #1 on: December 11, 2017, 01:59:30 PM »

i have always done it myself. Just unwind it and count the turns on each winding. it don't have to be perfect to work.

john N8QPC
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WBear2GCR
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« Reply #2 on: December 13, 2017, 01:18:53 PM »

The first question is straight wound or pi wound??
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n1ps
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Zorch!


« Reply #3 on: December 13, 2017, 08:41:53 PM »

I recently wound my own for an AA5 receiver.  I used a 1" ring ferrite with abt 50 turns to get abt 1mH inductance.  So a bifilar coil with 2, 10-90 pf mini tuning caps.  I located the caps and bandwidth resistors inside the can, using the original base.  I located the coil under the chassis.  Overall very pleased with performance.  In fact I have another one with a bad 455 can and doing the same thing. 

You need to add resistors to reduce the Q of the circuit to get the needed bandwidth.  I used 82K which worked well for the AM BC band.

The IF cans go bad frequently in the 50s and 60s sets.  They used layered mica in the base of the cans and sooner or later the mica shorts out from one side to the other.  You can tell as the grid goes positive for the output side.

Hope this helps.

Peter

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WZ1M
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« Reply #4 on: December 14, 2017, 03:38:23 AM »

Model and part number???
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n1ps
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Zorch!


« Reply #5 on: December 14, 2017, 07:53:33 PM »

The receiver I made the home brew 455 xformer was a Hallicrafters, typical Ktran type IF can.   You can try to rewind one of the Ktran coils (1 of 2), but it uses litz wire and about 600 turns each.  R U sure it is a coil issue? 
~ps
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wa2pjp
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« Reply #6 on: December 16, 2017, 10:23:12 AM »

It is the T-1 or T-3 IF coil in the Hallicrafters SX-88 part # 50C603....There is so much glue surrounding the coil, I can't unwind it to count the turns without damaging the coil further. pi wound.
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WBear2GCR
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« Reply #7 on: December 16, 2017, 11:03:40 AM »

Good clear image?

Possibly the "glue" can be dissolved, leaving the coil + enamel behind.
It may be "styrene" coil dope??
In which case there are solvents that will work on the styrene and not the enamel...

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wa2pjp
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« Reply #8 on: December 16, 2017, 03:50:32 PM »

Well.........coil reads open on an ohm meter and one side show burn marks, so I'm pretty sure it's a coil issue.
Bear, I was going to try a solvent, just so I can unwind and maybe fix the open and count the turns to try to rewind. have to find that wire though.
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n1ps
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Zorch!


« Reply #9 on: December 16, 2017, 07:58:36 PM »

An SX88...wow very rare Joe.  The stuff around the coils is wax.  You can count and hope the open is close by, but it can be anywhere in the roughly 600 turn coil.  I have a couple  NOS 455 cans on hand I found at some of the festers.  But After 3-4 IF cans went bad this year I decided to wind my own and save the cans.  An 88 is worth giving up a can.....so I can send you one.  I like my home brew version so much I dont not see a need to save them.

Peter
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KB1VWC
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« Reply #10 on: December 17, 2017, 07:39:10 AM »

  Joe, 

Could you use an IF can out of a Heathkit Pawnee or Shawnee? They use a 2MHz IF Strip. If you don't have a scrapper available, I could donate one to the cause. You probably could just pull the guts and install it in the Hallicrafters can.

   Steve
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KD6VXI
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« Reply #11 on: December 17, 2017, 05:06:36 PM »

Hey,

I bought a TON of boat anchor parts (seriously, it was a little over a quarter ton, 600 lbs).

I have a few if cans.

If you have some identifying marks, a type number, something for me to look for, I'd be happy to.

I'm not into receivers, so if I have what you need, cover postage.

--Shane
KD6VXI


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kb4qaa
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« Reply #12 on: December 17, 2017, 06:29:56 PM »

Chinese hand cranked coil winders are available on eBay for around $50.  I have one I have used for making coils for my 1929 TNT transmitter.  There are reliable company stores on eBay who sell enamel magnet wire in all sizes.

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w3jn
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« Reply #13 on: December 17, 2017, 07:08:30 PM »

I'm betting the first IF (1650KC) xformers from a SX-100 or SX-101 will work, changing the internal caps from 390 to 300 pF.

At least it's not a 50 kc transformer....
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WZ1M
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« Reply #14 on: December 18, 2017, 02:37:33 AM »

Be very careful on any auction sites when buying magnet wire. My experience has been that these mostly are factory seconds or have some type of defect in the insulation or wire size. I did buy some magnet wire, advertised as #38 and when it arrived, it was #40. Other wire I had bought from an auction site had bumps in the insulation coating and some places were bare. It wont take that much to wind the coil so you wont need 10 lbs. Mike at "CLEAR SIGNAL PRODUCTS" would be the guy to ask for small amounts of coated magnet wire.
Regards,
TRS
Gary
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