Removing Damaged RF Coil "Slugs" - UK Vintage Radio Repair and Restoration Discussion Forum

Mach One · 17th Jul 2020, 1:01 pm

I have been attempting to line up the RF coils of a Grundig Concert Boy 1100. When I got to one coil, the ferrite core split as I was attempting to adjust it. It is now impossible - for now at least - to remove it and replace it (I have spares...).

Does anyone have a good work around given how fragile these little coils and their formers are?

Leon Crampin · 17th Jul 2020, 1:50 pm

A hot air gun applied with discretion usually frees Grundig RF coils, which generally seem to be locked with wax. Heating a screwdriver blade with a soldering iron is another approach. Care is needed - although the cores will usually withstand heat, low loss polystyrene formers will not.

Leon.

Mach One · 17th Jul 2020, 4:08 pm

Two picture attached - for interest.

First one taken with an iPhone and the second one with a DSLR. As you can see I have had a go...

I have a spare core or two in an identical but faulty chassis - I was just looking at a much more sure way of swapping the bad ones out and the good ones in.

Do they go more crumbly with age?

vinrads · 18th Jul 2020, 10:41 am

I bet it's not far out of alignment , either leave it as is , or drill a small hole and glue a small screw filed down to a rectangle so it so it grip's ,I have done this using super glue , best of luck Mick.

Leon Crampin · 18th Jul 2020, 2:05 pm

Take your time freeing the core from your spare set - hot air, solvent, curses etc. When free, swap the coils over.

Leon.

Ian - G4JQT · 18th Jul 2020, 2:52 pm

If it hasn't split and wedged itself into the threaded sides, I've had success using a Dremel-type mini drill and waggled a 1mm drill bit side-to side to cut a small slot in the top. If the above suggested releasing techniques work it should then unscrew.

As a general rule, if you don't have spares and the core is intact there's usually another slot at the other end.

Goldieoldie · 18th Jul 2020, 9:01 pm

If the crack is clean try a tiny tiny drop of super glue to stick the core back together
Don’t use too much of you might glue the core to the former !
Then use a soldering iron on the core to soften the wax but not too much or you will melt the former if it’s plastic
IPA can also help to free slugs

17th Jul 2020, 1:01 pm	#1
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Removing Damaged RF Coil "Slugs" I have been attempting to line up the RF coils of a Grundig Concert Boy 1100. When I got to one coil, the ferrite core split as I was attempting to adjust it. It is now impossible - for now at least - to remove it and replace it (I have spares...). Does anyone have a good work around given how fragile these little coils and their formers are?

17th Jul 2020, 1:50 pm	#2
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Removing Damaged RF Coil "Slugs" A hot air gun applied with discretion usually frees Grundig RF coils, which generally seem to be locked with wax. Heating a screwdriver blade with a soldering iron is another approach. Care is needed - although the cores will usually withstand heat, low loss polystyrene formers will not. Leon.

17th Jul 2020, 4:08 pm	#3
Mach One Heptode Join Date: Sep 2005 Location: Shoreham-by-Sea, West Sussex, UK. Posts: 611	Re: Removing Damaged RF Coil "Slugs" Two picture attached - for interest. First one taken with an iPhone and the second one with a DSLR. As you can see I have had a go... I have a spare core or two in an identical but faulty chassis - I was just looking at a much more sure way of swapping the bad ones out and the good ones in. Do they go more crumbly with age? Attached Thumbnails

18th Jul 2020, 10:41 am	#4
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,766	Re: Removing Damaged RF Coil "Slugs" I bet it's not far out of alignment , either leave it as is , or drill a small hole and glue a small screw filed down to a rectangle so it so it grip's ,I have done this using super glue , best of luck Mick.

18th Jul 2020, 2:05 pm	#5
Leon Crampin Octode Join Date: Nov 2005 Location: Surrey, UK. Posts: 1,874	Re: Removing Damaged RF Coil "Slugs" Take your time freeing the core from your spare set - hot air, solvent, curses etc. When free, swap the coils over. Leon.

18th Jul 2020, 2:52 pm	#6
Ian - G4JQT Octode Join Date: Jun 2004 Location: Reading/Fakenham, UK. Posts: 1,326	Re: Removing Damaged RF Coil "Slugs" If it hasn't split and wedged itself into the threaded sides, I've had success using a Dremel-type mini drill and waggled a 1mm drill bit side-to side to cut a small slot in the top. If the above suggested releasing techniques work it should then unscrew. As a general rule, if you don't have spares and the core is intact there's usually another slot at the other end.

18th Jul 2020, 9:01 pm	#7
Goldieoldie Octode Join Date: Jul 2014 Location: Petersfield, Hampshire, UK. Posts: 1,043	Re: Removing Damaged RF Coil "Slugs" If the crack is clean try a tiny tiny drop of super glue to stick the core back together Don’t use too much of you might glue the core to the former ! Then use a soldering iron on the core to soften the wax but not too much or you will melt the former if it’s plastic IPA can also help to free slugs