Toko Coil formers - UK Vintage Radio Repair and Restoration Discussion Forum

Wendymott · 26th Feb 2021, 5:18 pm

Hi Peeps.
10 X 10mm Toko coil formers have been a staple component of mine for quite a while...... They are useful in so many ways...... mainly I.F tuning and RF front ends. In my storage I call them 421's and K3333. The 421's are the low frequency version, typically 455 Khz and such I.F usage... these are visually noted with a large outer core and a flat screwdriver slot to adjust. The K3333's are for HF, with.. maybe an un adjustable ferrite sleeve and an adjustable threaded core. Ok so far.....I need a variation of coils for my Eddy EC10 rebuild, the 421's are ok for the lower 2 ranges, i.e 0.55 - 1.5 Mhz and 1.5 - 3.5 Mhz. However the 421's are not suitable above these frequencies.... I wont say how I found out THAT one.. so I chose K3333's. The problem with this type of former is that it has partitions... see photo. This limits the thickness of wire and the number of turns...
I took to giving this problem a "coat of looking at" ...how to remove the inner cheeks or divisions..... I made a holder with an M3 bolt through the former with suitable clamping, and went to the lathe....it was obvious for 5 mins in that this was not going to work.
I then tried a sharp craft knife..... OK but slow..... then I tried to speed it up, using my soldering iron to part melt the dividers...... too coarse.... you dont really know what you are melting.... opppssss too late..
Back to a sharp craft knife...nothing is worth having unless you have put time into it, I carefully removed the inner dividers and with a small file to finish off, the former on the left is the result

I may be missing something, but why the dividers ? I have increased the capacity of the formers by at least 100%, I can now have the required turns with an increase of wire diameter to increase the "Q"...... I cannot see a minus here, except time spent.
Are there other 10mm formers out there without dividers ?? available to us amateurs with limited funds ??
I am a great fan of these formers, as they are not too large, easy to wind / rewind, and still available from various sources.

Ed_Dinning · 26th Feb 2021, 5:24 pm

Hi Wendy, any contacts with 3D printers?

Ed

Wendymott · 26th Feb 2021, 5:30 pm

Hi Ed........ Noooooooooooooooo... I cannot bear the thought of 3 hours for 1 coil former.. but an idea

Wendymott · 27th Feb 2021, 3:12 pm

Hi peeps. Further to the Toko coil saga.... I modified my coil winder slightly to make winding Toko coils a bit easier...... I found that manually winding was a lot untidy and may restrict the number of turns possible. 10 minutes on the lathe, a new shaft and there it is

When I edited my photo's they were all correct in rotation..... somehow they get rotated when posting...... Mod please advise.

Wendymott · 1st Mar 2021, 12:22 pm

Hi peeps.. Further research on Toko type formers... reveals some anomalies. I had bought a box of 100.. 10 X 10 formers from an ebay vendor a while back..... they are the K3333 type.... or so I thought. The physical layout is the same, but the dimensions are slightly different, and I must conclude that either they are a later Toko, or made by some other. The differences are....Taller, as the former is about 3mm longer, the inner dividing cheeks are thicker, but just as easy to remove, the inner ferrite core is also larger diameter, and has a hex slot rather than flat slot. The main annoying difference is that the Genuine Toko pin spacing is slightly wider, and thus the pcb foot print is not compatible, But saying all that, I can get more turns or thicker wire per inductor which is helpful. I also tried to identify the thread pitch on the cores. It seems my thread gauge has no comparable size. I guess its a UNC thread, certainly not metric.

Ed_Dinning · 1st Mar 2021, 10:05 pm

Hi Wendy, you should be able to find at least the pitch with your thread gauges, but not necessarily get a good fit if the pitch angles are different (UNC/ Metric/ Whit).
That said in Machinery's Handbook there are a huge number of special purpose threads listed for many weird and wonderful purposes, as well as quite a few that were Japanese specific.

Ed

Wendymott · 1st Mar 2021, 10:48 pm

Its always the case Ed.. I was hoping to find a tap.... to enable me to thread some home made formers .... cest la vie...

26th Feb 2021, 5:18 pm	#1
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Toko Coil formers Hi Peeps. 10 X 10mm Toko coil formers have been a staple component of mine for quite a while...... They are useful in so many ways...... mainly I.F tuning and RF front ends. In my storage I call them 421's and K3333. The 421's are the low frequency version, typically 455 Khz and such I.F usage... these are visually noted with a large outer core and a flat screwdriver slot to adjust. The K3333's are for HF, with.. maybe an un adjustable ferrite sleeve and an adjustable threaded core. Ok so far.....I need a variation of coils for my Eddy EC10 rebuild, the 421's are ok for the lower 2 ranges, i.e 0.55 - 1.5 Mhz and 1.5 - 3.5 Mhz. However the 421's are not suitable above these frequencies.... I wont say how I found out THAT one.. so I chose K3333's. The problem with this type of former is that it has partitions... see photo. This limits the thickness of wire and the number of turns... I took to giving this problem a "coat of looking at" ...how to remove the inner cheeks or divisions..... I made a holder with an M3 bolt through the former with suitable clamping, and went to the lathe....it was obvious for 5 mins in that this was not going to work. I then tried a sharp craft knife..... OK but slow..... then I tried to speed it up, using my soldering iron to part melt the dividers...... too coarse.... you dont really know what you are melting.... opppssss too late.. Back to a sharp craft knife...nothing is worth having unless you have put time into it, I carefully removed the inner dividers and with a small file to finish off, the former on the left is the result I may be missing something, but why the dividers ? I have increased the capacity of the formers by at least 100%, I can now have the required turns with an increase of wire diameter to increase the "Q"...... I cannot see a minus here, except time spent. Are there other 10mm formers out there without dividers ?? available to us amateurs with limited funds ?? I am a great fan of these formers, as they are not too large, easy to wind / rewind, and still available from various sources. Attached Thumbnails __________________ Should get out more. Regards Wendy G8BZY

26th Feb 2021, 5:24 pm	#2
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Toko Coil formers Hi Wendy, any contacts with 3D printers? Ed

26th Feb 2021, 5:30 pm	#3
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Coil formers Hi Ed........ Noooooooooooooooo... I cannot bear the thought of 3 hours for 1 coil former.. but an idea __________________ Should get out more. Regards Wendy G8BZY

27th Feb 2021, 3:12 pm	#4
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Coil formers Hi peeps. Further to the Toko coil saga.... I modified my coil winder slightly to make winding Toko coils a bit easier...... I found that manually winding was a lot untidy and may restrict the number of turns possible. 10 minutes on the lathe, a new shaft and there it is When I edited my photo's they were all correct in rotation..... somehow they get rotated when posting...... Mod please advise. Attached Thumbnails __________________ Should get out more. Regards Wendy G8BZY Last edited by Wendymott; 27th Feb 2021 at 3:13 pm. Reason: Question

1st Mar 2021, 12:22 pm	#5
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Coil formers Hi peeps.. Further research on Toko type formers... reveals some anomalies. I had bought a box of 100.. 10 X 10 formers from an ebay vendor a while back..... they are the K3333 type.... or so I thought. The physical layout is the same, but the dimensions are slightly different, and I must conclude that either they are a later Toko, or made by some other. The differences are....Taller, as the former is about 3mm longer, the inner dividing cheeks are thicker, but just as easy to remove, the inner ferrite core is also larger diameter, and has a hex slot rather than flat slot. The main annoying difference is that the Genuine Toko pin spacing is slightly wider, and thus the pcb foot print is not compatible, But saying all that, I can get more turns or thicker wire per inductor which is helpful. I also tried to identify the thread pitch on the cores. It seems my thread gauge has no comparable size. I guess its a UNC thread, certainly not metric. __________________ Should get out more. Regards Wendy G8BZY

1st Mar 2021, 10:05 pm	#6
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,194	Re: Toko Coil formers Hi Wendy, you should be able to find at least the pitch with your thread gauges, but not necessarily get a good fit if the pitch angles are different (UNC/ Metric/ Whit). That said in Machinery's Handbook there are a huge number of special purpose threads listed for many weird and wonderful purposes, as well as quite a few that were Japanese specific. Ed

1st Mar 2021, 10:48 pm	#7
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Coil formers Its always the case Ed.. I was hoping to find a tap.... to enable me to thread some home made formers .... cest la vie... __________________ Should get out more. Regards Wendy G8BZY