Source of replacement ferrite tuning slugs

[d***@drumheller.org]

I'm presently repairing a Knight-Kit Star Roamer LF/MF/shortwave
receiver, and while in the process of adjusting the oscillator coil
for the LF band, I broke its ferrite tuning slug. Previous posters
suggested gluing a wooden stick or toothpick into the hexagonally
shaped hole in the slug and twisting it out when the glue dries, but
this failed. I now have to chip it out and replace it.

QUESTION: Does anyone know of a source of threaded ferrite tuning
slug? I need ones that are about 1/2-inch long and 1/4-inch in
diameter. The oscillator coils in this set look like they were
manufactured by J.W. Miller.

-Dave Drumheller, K3WQ

[Ken]

Post by d***@drumheller.org
I'm presently repairing a Knight-Kit Star Roamer LF/MF/shortwave
receiver, and while in the process of adjusting the oscillator coil
for the LF band, I broke its ferrite tuning slug. Previous posters
suggested gluing a wooden stick or toothpick into the hexagonally
shaped hole in the slug and twisting it out when the glue dries, but
this failed. I now have to chip it out and replace it.
QUESTION: Does anyone know of a source of threaded ferrite tuning
slug? I need ones that are about 1/2-inch long and 1/4-inch in
diameter. The oscillator coils in this set look like they were
manufactured by J.W. Miller.
-Dave Drumheller, K3WQ

...

I have one that matches those dimensions, free if you want it. Ken
wklw at cox dot net

[Paul P]

I scrounge them from the junk bin. Some times they work some times they do
not. I try to keep some old trash day TVs as a source of such items.
Hamfests are a decent source of old chassis with ferrite cores.

Yeah, I know that really did not help you much right now..... :~)
Paul P

Post by d***@drumheller.org
I'm presently repairing a Knight-Kit Star Roamer LF/MF/shortwave
receiver, and while in the process of adjusting the oscillator coil
for the LF band, I broke its ferrite tuning slug. Previous posters
suggested gluing a wooden stick or toothpick into the hexagonally
shaped hole in the slug and twisting it out when the glue dries, but
this failed. I now have to chip it out and replace it.
QUESTION: Does anyone know of a source of threaded ferrite tuning
slug? I need ones that are about 1/2-inch long and 1/4-inch in
diameter. The oscillator coils in this set look like they were
manufactured by J.W. Miller.
-Dave Drumheller, K3WQ

...

[d***@drumheller.org]

Post by Paul P
I scrounge them from the junk bin. Some times they work some times they do
not. I try to keep some old trash day TVs as a source of such items.
Hamfests are a decent source of old chassis with ferrite cores.
Yeah, I know that really did not help you much right now..... :~)
Paul P

Well, that's OK. It's the answer I should have expected all along.

Last night I noticed my shop radio, a working AM/FM junker without a
cabinet, has IF transformers with what appear to be the same type of
slug. I guess it's time to pull the slugs and retire the chassis to
the bone yard.

-Dave Drumheller, K3WQ

[Randy or Sherry Guttery]

Post by d***@drumheller.org
Last night I noticed my shop radio, a working AM/FM junker without a
cabinet, has IF transformers with what appear to be the same type of
slug. I guess it's time to pull the slugs and retire the chassis to
the bone yard.

At least until you can find slugs to put back in. Use whatever slugs
you can find to get the radio you're working on fixed - note what you
need for the "donor" and keep a watchful eye for replacements.

I mean - how many radios can you listen to at one time?

[d***@drumheller.org]

Post by Randy or Sherry Guttery

Post by d***@drumheller.org
Last night I noticed my shop radio, a working AM/FM junker without a
cabinet, has IF transformers with what appear to be the same type of
slug. I guess it's time to pull the slugs and retire the chassis to
the bone yard.

At least until you can find slugs to put back in. Use whatever slugs
you can find to get the radio you're working on fixed - note what you
need for the "donor" and keep a watchful eye for replacements.
I mean - how many radios can you listen to at one time?

...

Only one, of course.

Actually, I'm glad this has happened because I no longer have any
reason to keep the junker's shattered and incomplete plastic cabinet
around to harbor the foolish hope that one day I will glue it back
together to produce a flawless restoration.

-Dave Drumheller, K3WQ

[John Byrns]

Post by d***@drumheller.org

Post by Randy or Sherry Guttery
I mean - how many radios can you listen to at one time?

Only one, of course.

I don't know if that is correct, I used to regularly listen to two
radios at once, and even tried three on several occasions although not
with a great degree of success. It's been years since my days of
listening to two radios at one time. It's an interesting question
though, can most people only listen to one radio at a time?


Regards,

John Byrns

[Uncle Peter]

Post by d***@drumheller.org
Last night I noticed my shop radio, a working AM/FM junker without a
cabinet, has IF transformers with what appear to be the same type of
slug. I guess it's time to pull the slugs and retire the chassis to
the bone yard.
-Dave Drumheller, K3WQ

For LF the slugs will probably be ferrite as you noted, but becareful
that ones your scrounging aren't powered iron which are used in the mid
to upper HF ranges.. They won't give you enough inductance.

Pete

[robert casey]

Post by d***@drumheller.org
I'm presently repairing a Knight-Kit Star Roamer LF/MF/shortwave
receiver, and while in the process of adjusting the oscillator coil
for the LF band, I broke its ferrite tuning slug. Previous posters
suggested gluing a wooden stick or toothpick into the hexagonally
shaped hole in the slug and twisting it out when the glue dries, but
this failed. I now have to chip it out and replace it.

Most anything from a transformer of similar frequency and physical size
(including the threads per inch) will work.

You have to use the exact tool for adjusting these things, else it will
break, as you learned... :-(

[Uncle Peter]

Post by robert casey

Post by robert casey
You have to use the exact tool for adjusting these things, else it will

break, as you learned... :-(

We had an instructor that told us to throw away our alignment tools and
buy new ones every so often. Worn edges on hex alignment plastic tools
will stress and crack the slugs just as easily as the "wrong" tool surely
will.

Pete

[d***@drumheller.org]

Post by Uncle Peter
We had an instructor that told us to throw away our alignment tools and
buy new ones every so often. Worn edges on hex alignment plastic tools
will stress and crack the slugs just as easily as the "wrong" tool surely
will.
Pete

...one step ahead of you, Pete. I stopped by Radio Shack--don't
laugh!--over lunch and picked up a new set of alignment tools that
includes the appropriate male hex wrench for the job.

Stress is a reasonable explanation for why these ferrite slugs crack;
however, are there other possible causes? Could it be that the paper
bobbins on which the coils are wound shrink over time?

-Dave, K3WQ

[Michael A. Terrell]

Post by d***@drumheller.org

Post by Uncle Peter
We had an instructor that told us to throw away our alignment tools and
buy new ones every so often. Worn edges on hex alignment plastic tools
will stress and crack the slugs just as easily as the "wrong" tool surely
will.
Pete

...one step ahead of you, Pete. I stopped by Radio Shack--don't
laugh!--over lunch and picked up a new set of alignment tools that
includes the appropriate male hex wrench for the job.
Stress is a reasonable explanation for why these ferrite slugs crack;
however, are there other possible causes? Could it be that the paper
bobbins on which the coils are wound shrink over time?
-Dave, K3WQ

...

No, but they do dry out. There was a lubricating film when they were
new. One old trick was to slip an Allen wrench into the slug and gently
heat it up, to soften the remaining lube. A tiny bit of paraffin or
other dry lube makes it easier to adjust. Just don't use too much, or
it'll cause the core to stick, even worse.

[Paul P]

Post by d***@drumheller.org
Stress is a reasonable explanation for why these ferrite slugs crack;
however, are there other possible causes? Could it be that the paper
bobbins on which the coils are wound shrink over time?
-Dave, K3WQ

Sometimes I use a soldering iron plugged into my dim bulb tester to make it
just hot enough to soften the wax that is dropped into the core
(Transoceanic). Then I use a sharp Craftsman metal hex tool to loosen up
the slug or a metal small Exlite screw driver. Then I use a proper
alignment tool on the freed up slug.

And sometimes I risk it all on the video bonus question and go for double or
nothing and just crank on the slug with out preparing it. Then like others
crack it.

PP

[Michael A. Terrell]

Post by Uncle Peter

Post by robert casey

Post by robert casey
You have to use the exact tool for adjusting these things, else it will

break, as you learned... :-(

We had an instructor that told us to throw away our alignment tools and
buy new ones every so often. Worn edges on hex alignment plastic tools
will stress and crack the slugs just as easily as the "wrong" tool surely
will.
Pete

http://www.coilcraft.com/tools.cfm

[Michael A. Terrell]

Post by d***@drumheller.org
I'm presently repairing a Knight-Kit Star Roamer LF/MF/shortwave
receiver, and while in the process of adjusting the oscillator coil
for the LF band, I broke its ferrite tuning slug. Previous posters
suggested gluing a wooden stick or toothpick into the hexagonally
shaped hole in the slug and twisting it out when the glue dries, but
this failed. I now have to chip it out and replace it.
QUESTION: Does anyone know of a source of threaded ferrite tuning
slug? I need ones that are about 1/2-inch long and 1/4-inch in
diameter. The oscillator coils in this set look like they were
manufactured by J.W. Miller.
-Dave Drumheller, K3WQ

...

http://www.lodestonepacific.com/distrib/pdfs/Micrometals/RFA_Cat.pdf

[Tim Mullen]

Post by Michael A. Terrell
http://www.lodestonepacific.com/distrib/pdfs/Micrometals/RFA_Cat.pdf

Cool. Ferrite cores always seemed like one of those coat hanger
things -- no one reallly knows where they come from. :)

What's the best way to make a clean cut in this material? Hacksaw?
Dremel cut-off wheel?

(I like their product line: Toroid Mounts, Core Materials, and a
High-Quality, Low-Cost Video Conference System...)

[Michael A. Terrell]

Post by Tim Mullen

Post by Michael A. Terrell
http://www.lodestonepacific.com/distrib/pdfs/Micrometals/RFA_Cat.pdf

Cool. Ferrite cores always seemed like one of those coat hanger
things -- no one reallly knows where they come from. :)
What's the best way to make a clean cut in this material? Hacksaw?
Dremel cut-off wheel?

I've never seen anyone do a clean cut in a slug. If you look at that
PDF, they make about any length in the material you need, so why try to
cut them? Being a magnetic material, you might change the properties.
I've seen ferrite rod scored with a triangle file and snapped, but
unless you went most of the way around, it may snap at an angle.

Just remember that yo want Ferrite for IF and most HF applications.
Powdered Iron is not suitable for most tunable RF applications for old
radios. I think that Fair-Rite made the cores used by J.W. Miller for
their replacement IF transformers and Local Oscillator coils. I wish
that I could find a source for the paper tubes, to make replacement
coils that look like the originals. After all, if Syl can rebuild phono
carts, why shouldn't someone be able to custom wind replacement coils?
I have over 100 stepper motors, and plenty of computer junk to build as
programmable winding machine

[d***@drumheller.org]

Post by Michael A. Terrell
Just remember that yo want Ferrite for IF and most HF applications.
Powdered Iron is not suitable for most tunable RF applications for old
radios. I think that Fair-Rite made the cores used by J.W. Miller for
their replacement IF transformers and Local Oscillator coils. I wish
that I could find a source for the paper tubes, to make replacement
coils that look like the originals. After all, if Syl can rebuild phono
carts, why shouldn't someone be able to custom wind replacement coils?
I have over 100 stepper motors, and plenty of computer junk to build as
programmable winding machine

...

Thanks for the link to the Micrometals catalog. The type of
replacement cores we've been discussing are listed on page 22.

Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.

-Dave Drumheller, K3WQ

[Michael A. Terrell]

Post by d***@drumheller.org

Post by Michael A. Terrell
Just remember that yo want Ferrite for IF and most HF applications.
Powdered Iron is not suitable for most tunable RF applications for old
radios. I think that Fair-Rite made the cores used by J.W. Miller for
their replacement IF transformers and Local Oscillator coils. I wish
that I could find a source for the paper tubes, to make replacement
coils that look like the originals. After all, if Syl can rebuild phono
carts, why shouldn't someone be able to custom wind replacement coils?
I have over 100 stepper motors, and plenty of computer junk to build as
programmable winding machine

Thanks for the link to the Micrometals catalog. The type of
replacement cores we've been discussing are listed on page 22.
Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.
-Dave Drumheller, K3WQ

...

Have you ever tried to replace one when the slot is damaged? Its
even worse than the hex types. They damage the plastic forms, so i
surely wouldn't want to remove one from a paper form.

As far as the mix goes Micrometals they have a chart telling yo which
mixes are made for what ranges.

http://www.micrometals.com/materialchart.html

[d***@drumheller.org]

Post by Michael A. Terrell

Post by d***@drumheller.org
Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.
-Dave Drumheller, K3WQ

Have you ever tried to replace one when the slot is damaged? Its
even worse than the hex types. They damage the plastic forms, so i
surely wouldn't want to remove one from a paper form.

...

I hadn't thought of that--good point.

I checked out the Micrometals web site and have the impression that
it's one of those we-don't-do-business-with-small-guys outfits. Have
you ever done business with this company? If so, how? If not, then
how have you (could you) acquire its products?

-Dave Drumheller, K3WQ

[Michael Black]

Post by d***@drumheller.org

Post by Michael A. Terrell

Post by d***@drumheller.org
Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.
-Dave Drumheller, K3WQ

Have you ever tried to replace one when the slot is damaged? Its
even worse than the hex types. They damage the plastic forms, so i
surely wouldn't want to remove one from a paper form.

I hadn't thought of that--good point.
I checked out the Micrometals web site and have the impression that
it's one of those we-don't-do-business-with-small-guys outfits. Have
you ever done business with this company? If so, how? If not, then
how have you (could you) acquire its products?

...

But that's where Amidon rose up, over forty years ago.

Their intent was to provide toroids (and I think later other cores)
in single quantities, starting from when few hobbyists even knew what
toroids were, and nobody else was selling in single quantities. "Amidon"
basically became a brand name, but they were never a manufacturer, only
a reseller. But they dominated the field because they were visible and
sold in single quantities.

So whoever they buy from, and I can never remember, is fairly anonymous,
while people talk in terms of "Amidon toroids".

Michael

[John Doty]

Post by Michael Black

Post by d***@drumheller.org

Post by Michael A. Terrell

Post by d***@drumheller.org
Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.
-Dave Drumheller, K3WQ

Have you ever tried to replace one when the slot is damaged? Its
even worse than the hex types. They damage the plastic forms, so i
surely wouldn't want to remove one from a paper form.

I hadn't thought of that--good point.
I checked out the Micrometals web site and have the impression that
it's one of those we-don't-do-business-with-small-guys outfits. Have
you ever done business with this company? If so, how? If not, then
how have you (could you) acquire its products?

But that's where Amidon rose up, over forty years ago.
Their intent was to provide toroids (and I think later other cores)
in single quantities, starting from when few hobbyists even knew what
toroids were, and nobody else was selling in single quantities. "Amidon"
basically became a brand name, but they were never a manufacturer, only
a reseller. But they dominated the field because they were visible and
sold in single quantities.

...

Yes, Amidon is probably your best choice if you're not ordering 10,000.
They have the connections to deal with the Micrometals of the world, but
they're used to small volume sales. They may know better than anyone
in this forum what it is you need, too.

It's not only hobbyists that need small quantities. Some years ago, when
I needed a couple of toroids to put in a satellite (HETE-2), I got them
from Amidon.

[Michael A. Terrell]

Post by d***@drumheller.org

Post by Michael A. Terrell

Post by d***@drumheller.org
Mike (or anybody), can you recommend which mix is most suitable for
replacing cores from 1950s and 1960s vintage sets that seem to use hex-
slotted cores? Also, I'd be tempted to use the solid cores with a
full-slot as replacements, as they may be less likely to break under
stress.
-Dave Drumheller, K3WQ

Have you ever tried to replace one when the slot is damaged? Its
even worse than the hex types. They damage the plastic forms, so i
surely wouldn't want to remove one from a paper form.

I hadn't thought of that--good point.
I checked out the Micrometals web site and have the impression that
it's one of those we-don't-do-business-with-small-guys outfits. Have
you ever done business with this company? If so, how? If not, then
how have you (could you) acquire its products?
-Dave Drumheller, K3WQ

...

We bought from them at my last job but I didn't spend much time
working with purchasing, other than to qualify or provide information to
remove a vendor from the "Approved Vendor list".


Most of Micrometals distributors provide samples, and you might get a
few for free if you contact Micrometals and ask politely.


If I could afford it, I would put together an assortment of
replacement slugs, and ask the users to help build a database of what
slugs work in the radios they repair.


One thing to watch out for: Some applications are on the ends of two
mixes, and you might need to try both to find the best choice.