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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 28th Jul 2020, 7:06 am   #1
Join Date: Oct 2005
Location: Olympia, Washington, USA.
Posts: 474
Default Stuck Ferrite IF cores.

We all have run into this from time to time.
I ran into a lot of this in TV servicing and old radios.

That "delightful" hex hole core was stuck. Often from hot glue, or more commonly beeswax or silicone seal.

Getting a stuck core out can try the patients of a Doctor (LOL).

I found sometimes pouring some denatured alcohol into the core would loosen it, but more often digging out the silicone seal, or hot glue- and heating the coil carefully with a heat gun to melt the bees wax out.
Sometimes putting in a nail filed to the core shape and heated would loosen the beeswax quite quickly too.

Then comes that sound we all dread... Crunch! When the core breaks into a pile of ferrite pieces.
I learned decades ago that this was way more common than I liked. So I started removing the adjustable ferrite cores from old TV and radio chassis, 2 way radios, etc.
I would carry a box of them of assorted diameters and lengths in my service kit. (GC- General Cement, used to make a kit of assorted replacement cores).

The core you need too long? File it down or use sand paper to reduce the length. Too short? Put 2 cores snug with each other, and cement together with ferrite cement. Then put in the coil form.

Now I never found any problem with ferrite mix causing a problem in the coils. Sometimes I'd have to adjust the core to a different spot to get the correct adjustment, due to the replacement core being a bit longer, shorter, etc; but it never failed me.

Oh, and carry a few VERY thin rubber bands in your kit too. Some cores used a thin strip of rubber band to "lock" the core in place. No glue, silicone, or beeswax needed. I did carry a small ball of bees wax to seat the cores with and wax dial cords too.

The very last thing I wanted to do was replace a good coil with a replacement just because of a broken core.
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Old 28th Jul 2020, 8:54 am   #2
SeanStevens's Avatar
Join Date: Sep 2009
Location: Bath, Somerset, UK.
Posts: 893
Default Re: Stuck Ferrite IF cores.

I have a transistor radio that needs 3 or 4 cores replaced. They are not broken yet, but will be if I try any harder to get them out.

Does anybody sell slug replacement sets still?

There are only 10 types of people, those who understand the binary system, and those who don't.
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Old 29th Jul 2020, 2:06 pm   #3
Join Date: Apr 2016
Location: Cheltenham, Gloucestershire, UK.
Posts: 670
Default Re: Stuck Ferrite IF cores.

Some people also recommend eardrops [i.e. those intended to dissolve and/or dislodge wax] .........? Hear! Hear!
Red to red, black to black. Throw the switch and stand well back!
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