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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 13th Mar 2008, 9:52 am   #1
MichaelR
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Default Stubborn tuning slugs

Hi,

Can anybody provide practical advice or advise techniques to "free off" IF tuning slugs that will not turn. The slugs are not broken and I would like it to remain that way and I need to adjust the IF's because I have had to rebuild the whole IF section.

Mike
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Old 13th Mar 2008, 10:20 am   #2
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Default Re: Stubborn tuning slugs

Hello Mike, I find that lighter fluid works very well. Gently drizzle it into the core and within seconds the slugs should begin to move.
Neil
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Old 13th Mar 2008, 11:01 am   #3
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Default Re: Stubborn tuning slugs

Mike

I find that a swift squirt of Servisol 10 softens any wax locking the core and lubricates the thread when making adjustments, preventing the core from jamming up on debris.

Ron
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Old 13th Mar 2008, 1:00 pm   #4
Leon Crampin
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Default Re: Stubborn tuning slugs

Ear wax remover.

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Old 13th Mar 2008, 2:12 pm   #5
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Default Re: Stubborn tuning slugs

I've used ear wax remover and Three-In-One on occasions. It's best to set IFTs so that gravity helps. You really only want whatever solvent you use in the core, not anywhere else. You can always add a drop more later if you need it, but getting rid of excess is a nuisance and it might do damage.

The other thing is get or make an adjustment tool which fits the slot properly, that way you distribute the pressure evenly and there's less chance of crumbling the core.

Pete.
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Old 13th Mar 2008, 5:39 pm   #6
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Question Re: Stubborn tuning slugs

And arising from this Thread - if you do have a cracked core / tuning slug - what's the best way of removing it?

Al / Skywave.
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Old 13th Mar 2008, 5:42 pm   #7
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Default Re: Stubborn tuning slugs

Grind it out with a dentist's burr held in a Dremel type tool.
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Old 13th Mar 2008, 6:56 pm   #8
Ray Cooper
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Default Re: Stubborn tuning slugs

Quote:
...The other thing is get or make an adjustment tool which fits the slot properly, that way you distribute the pressure evenly and there's less chance of crumbling the core...
In order to preserve your sanity as well as the cores, it is essential to use a tool that fits the screwdriver slot (or hexagonal core hole, according to style) of any dust/ferrite type of core. Once the slot's gone, or damaged, the core becomes unturnable. If you use excessive force on the hex-core type, the thing can easily split and this causes the two halves to be forced apart when you try to adjust the thing, thus forming a fine friction brake...

A tip that I came across some years ago may be helpful: use two adjusting tools, applied to opposing ends of the core simultaneously, whenever possible. You can then apply much more force to the tools, thus keeping them in the slot/hole more firmly, whilst removing the frictional force between the core's thread and the coil former: the core magically becomes very much easier to turn...
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Old 13th Mar 2008, 7:13 pm   #9
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Default Re: Stubborn tuning slugs

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Originally Posted by Ray Cooper View Post
A tip that I came across some years ago may be helpful: use two adjusting tools, applied to opposing ends of the core simultaneously, whenever possible.
What a good tip! Well worth remembering.
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Old 13th Mar 2008, 7:19 pm   #10
Sean Williams
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Default Re: Stubborn tuning slugs

Soldering iron tip on the core for a few seconds - shifts them every time!
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Old 13th Mar 2008, 8:55 pm   #11
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Default Re: Stubborn tuning slugs

Yes, but be certain that what you are touching with the iron really is a ferrite and isn't a plastic carrier. This happened to me a few years back with a PCR.

The other thing which happened, also with that PCR, is that the core seems to turn easily, but if you look carefully, you can see that the tube it's in also turns. The tube and coils are glued to a paxolin carrier and the glue can fail. Just turn the core and you will break a Litz wire, probably close to the coil. I smelt a rat and didn't fall into that trap.

The other thing I've had happen is that the plastic carrier can break and luckily it was just a careful job with superglue, but it could have been tragedy. It didn't take much to break it.


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Old 14th Mar 2008, 10:56 pm   #12
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Default Re: Stubborn tuning slugs

Thanks everybody for your suggestions. The ingenuity of man always amazes me!

After much struggle I had to resort to the dremel and grind them out . It looked as though somebody had heavily glued them in place , they would not move.Even this task was not easy

Mike
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Old 15th Mar 2008, 7:14 am   #13
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Default Re: Stubborn tuning slugs

I have a Pilot model 10 with one core that stubbornly refuses to move. Fortunately the alignment is good so I've left it alone. However I did have a look inside the transformer to investigate why it was so tight.....the coil former has SHRUNK! Maybe this is due to heat but more than likely the material it's made from (although it looks just like Paxolin). There is no way the core is going to move up or down. Anyone else come across this? I'm leaving it as it is anyway as the alignment is good.


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Old 15th Mar 2008, 10:43 am   #14
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Default Re: Stubborn tuning slugs

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Originally Posted by Richard_Newman View Post
I have a Pilot model 10 with one core that stubbornly refuses to move. Fortunately the alignment is good so I've left it alone. However I did have a look inside the transformer to investigate why it was so tight.....the coil former has SHRUNK! Maybe this is due to heat but more than likely the material it's made from (although it looks just like Paxolin). There is no way the core is going to move up or down. Anyone else come across this? I'm leaving it as it is anyway as the alignment is good.


Rich.
Hi Rich,

These had definitely been glued with some sort of evostick type glue. It was defininetly not wax. I was glad of the dremel suggestion ( station X) as with the dentist burr I was amazed at the degree of control I had with the removal of the core.

regards
Mike
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Old 15th Mar 2008, 12:43 pm   #15
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Default Re: Stubborn tuning slugs

Older equipment seems to have slugs sealed with wax which is generally fairly easy to remove. With more modern gear they seem to be sealed with some kind of paint or a blob of silicone sealant which is much more difficult to remove. Then of course some slugs have a strip of rubber embedded in the side.

On the whole I prefer sets where the slugs are attached to a threaded rod. True the slug sometimes detaches itself from the rod, but it can be glued back on again. Where such slugs have locknuts I don't bother to reseal them, This facilitates future readjustment and as long as the set is with me I know the phantom twiddler hasn't been at work. The threaded rods in the AR88 Comms receiver are sealed with a substance which goes rock hard. I think it may be shellac.

Don't try to drill out a slug with an ordinary twist drill. There is a risk it will "catch up" and split the slug. This then splits the former and may destroy the winding. If a slug has split it is sometimes possible to use a pair of very small thin nosed pliers or tweezers to pick out the bits, or crush them to make removal easier.

If a slug absolutely refuses to move you can check the alignment by introducing brass rod into the core to lower the inductance or another slug to raise it. This is easier with inductors having a single winding and a single core. More difficult with IF transformers.
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Old 16th Mar 2008, 12:23 am   #16
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Exclamation Re: Stubborn tuning slugs

Quote:
Originally Posted by Station X View Post
Don't try to drill out a slug with an ordinary twist drill. There is a risk it will "catch up" and split the slug.
Or worst still, the drill bit will slide off the top of the slug and go clean through the winding!

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Old 16th Mar 2008, 4:13 pm   #17
Leon Crampin
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Default Re: Stubborn tuning slugs

In one set I restored with a totally immovable slug, I was able to add a very small amount of additional parallel capacitance in order to bring the coil to the required resonant frequency (the frequency needed to come down). As a "trimmer" I just used about 1" of parallel twin bell wire and chopped little bits off it until it was correctly tuned. It took a few goes to get right, but it was a very non destructive bodge - far better than breaking something.

If the frequency had to go the other way, I would have changed the fitted parallel capacitor for one of a lower value.

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Old 17th Mar 2008, 5:31 pm   #18
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Default Re: Stubborn tuning slugs

Quote:
Originally Posted by Sean Williams View Post
Soldering iron tip on the core for a few seconds - shifts them every time!
Yes Sean the old soldering iron tip is the best I have never had a problem this way and after you've done your "twiddleing" some melted wax from your old TCC waxies will seal it all up again.
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