The AM Forum

Greetings from Old Shincracker,

I am doing the final alignment of the mixer stages on an HT-37 transmitter for a friend. Some of the slug tuned inductors are binding and chattering to such an extent that it is near impossible to find the peak output. What is the best method to cure this malady? Heat?, light weight oil, like WD40, sewing machine oil.. etc. etc?

Thanks for your consideration.

Peter
N2IDU

have you tried removing the slug and cleaning the threads on the slug and in the sleeve? 

I've just gone through this with a Heath S-119 receiver.

IMO, the answer is: no easy solution, and most likely things will turn out bad, i.e. cracked or stuck.

You don't want to use any liquid that will  be asborbed.  It seems the best recommendation I found was rubbing alcohol, which didn't help me at all.

In the end, 3 of 5 slugs were either cracked or cracked upon manipulation.  Close inspection shows all of them were crumbling and deteriorating material.  I bought an assortment of slug lengths from Nebraska Surplus Sales, no idea on mix. 

https://www.surplussales.com/Inductors/Ind-SlugTu/Ind-SlugTu-6.html

Slugs that moved partially turned out to be cracked and would shift and bind when rotated.

If excess wax is the problem a few moments application of a soldering pen may warm things enough to allow movement.

p.s.  To add to the fun, I'm having to rewind two coils without any specs.  This shifts circuit capacitance, so now I'm changing caps down the line.  :)

If the ferrite slug is good (not cracked or crumbing), sometimes you can insert a length of waxed string into the coil core and then insert the ferrite slug. The Japanese  manufacturers were doing this with their adjustable coils back in the "good old days" to keep the slugs from moving around especially with critical adjustments.

OK.... Well I appreciate the tips but will assume negative results. Cranking them out to remove them and then cleaning the inside threads is just about impossible inasmuch as they only get tighter and more jammed until they will not move at all. I don't think any of them shattered yet but who knows.
We will try heating them up as suggested by KB4qaa as this seems the best alternative. Any more post on the subject would sure be welcome!

Thanks to all.

Peter
N2IDU
Old Shincracker, Vt.

Once upon a time in the 70's Motorola sold us "slug lubricant" to use in RF transformers with ferrite cores in police mobile radios like Motracs and Motrans.   It was a white powder and I think all it was, was talcum powder.  Of course if the slug is already stuck, that won't help much.  Broken slugs are, I think, just a right of passage in radio education.

Peter,

Let me know what slug / coil you need for the HT-37 and if I have it I can send it to you.  I am the guy who previously sent you out the audio transformer for the HT-37. 

Joe, W3GMS   

Take the slugs out and rub them length wise on a block of paraffin or Bees wax to get some wax in the threads.  Rotate 180* and repeat.  I strongly advise against using any sort of liquid oil.