Frozen slugs et al

[Steve Harrison]

At 12:16 PM 2/21/99 -0500, Ray A. Allen, Sr. wrote:
>Gentle Keepers of the Green....
>
>        I be working on this SB102. T1 transformer, part number 52-79,
>(also found in whole bunch of other Heath Radios), 3.395 frequency
>has a single slug that is frozen tighter than Dick's Hatband.

Best solution, IMHO, is to just break the slug into pieces and replace it.
Slugs often freeze because they crack and then expand slightly as you
attempt to turn them with the wrench. If they freeze due to other internal
coil form damage (such as the cracked slug digging into the form), the
damage is often fatal to that particular slug in any case. But rarely to
the form itself.

The slugs in these transformers are nothing special at all; almost any
powdered iron and most ferrite slugs of the right diameter will work fine.
You should try to find one of the same length, of course. Try to find a
slug from a transformer or coil form of the same approximate frequency
range: i.e., for 455 kHz transformers, you probably will have to find a
slug from another VLF transformer or coil; for transformers between about
1.6 MHz and 30 MHz, something from a 9 MHz, 10.7 MHz or even 21.4 MHz
should work. (An excellent source of the 10.7 and 21.4 MHz types is a
grab-bag of transformers/coils or an old TV set).

Break the old slug by inserting a sharp tiny screwdriver onto the top edges
of the slug and tap on the screwdriver/pick/soldering tool with a small
wrench. The goal is to chip the slug into fragments that either fall
through the coil form or that you can shake out by turning the radio upside
down. DON'T try prying into the slug by inserting the tool between the slug
and paper coil form; you may distort the coil form and a replacement slug
might not screw up and down evenly!

Once you have the slug broken into a shorter length, you may be able to
either screw it the rest of the way out or push it out the top (it's not
usually a good idea to try pushing it out the bottom because many coil
forms are suspended ABOVE the bottom of the transformer lug insulation, and
the form may simply drop into the inside of the transformer. If this
happens, you usually can leave it there with no adverse effect other than
an annoying tiny rattle for-bloody-ever when you shake the radio!!).

Then clean out the inside of the form with a tissue or Q-Tip and maybe a
dab of alcohol; there will be dust from the slug inside which must be
removed lest it cause premature seizure of a replacement slug. I don't
bother trying to lubricate the inside of the form since it's NOT supposed
to be something that you are always adjusting! I don't know what the effect
might be if you were to try any lubrication, but I'd think a paper form
would begin falling apart as the glue disintegrated with the lubricant. If
you really want, you could try a tiny bit of soap or wax wiped along the
slug threads.

If your new slug seems to be a bit loose because the old coil form has been
worn by continual adjustment, then try inserting a piece of wax paper or
piece of lacing cord as you screw in the new slug. Once you have finished
realignment, you can cut off the excess paper or cord and hardly anybody
will be able to see it.

You don't like the idea of breaking the slug? Remember: if you succeed, you
will have avoided having to find a replacement transformer in GOOD shape;
and you will have avoided having to remove the old transformer, possibly
damaging something else along the way. Besides, it will probably take a lot
less time than replacing the whole transformer.

73, Steve Ko0U/1

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