Toko Type inductor test jig - UK Vintage Radio Repair and Restoration Discussion Forum

Wendymott · 12th Mar 2021, 11:20 pm

Hi Peeps. A few days ago I received a number of Toko Type inductors in the post from Jimbo.. one of our members.
However without opening every one.. its difficult to decide what they are good for, so I decided to make a test jig, specifically for Toko 5 pin formers.
I already had a fet buffer / impedance match for the Siglent Spectrum analyser / tracking generator , so it was easy to make another with an extra bit to accommodate the coils.
As the Siglent's Input impedance is 50 R a high impedance buffer is totally necessary, otherwise the tuned circuit is severely damped.
A trimmer cap of 6 - 25 pf is added to see what the tuning range could be.
The Siglent shows a 30 Mhz tuned inductor, obviously with a little bit of work to make adaptors any coil can be tested.

Another.. unwasted day

Electronpusher0 · 13th Mar 2021, 8:57 am

I love the way you have made a proper test jig in a box with a printed front panel.
I think most of us would have just lashed something together on the bench.

Peter

vinrads · 13th Mar 2021, 10:16 am

Very impressive , love it . Mick.

CambridgeWorks · 13th Mar 2021, 10:38 am

Very neat indeed. With a few coils to test now and maybe even more in the future it saves also the frustration of say miniature croc clips, push on connectors or soldered wires coming adrift. Especially if these are not noticed immediately, leading to head scratching as to why a coil isn't testing as expected.

Back in the 70s, I made a "handheld" (10" x 5" x 1.75") 2M transceiver all on one dalo printed and etched pcb. I had obtained a load of reject Toko coils from a scrapyard just outside Skegness. Rank, Bush Murphy I believe it was had a factory in Skegness.
Using a gdo, I managed to use some for the 8MHx osc, 24MHz tripler stages, plus the usual IF. I think I may still have a few somewhere.
I believe the reason for reject was they had been put in the wrong position, so discarded and a new one fitted.
Your test box would have been a handy item for me then!
Rob

Wendymott · 13th Mar 2021, 11:40 am

Thanks Mick, Peter and Rob. I am very fortunate to have the time..... my personal "no no" is "dead bug".... ok for trial and test but not as a final item. There are a lot of good constructors on this forum

.
I was brought up on the "if it looks Right" philosophy..... I spent a lot of my working life making prototypes and Test jigs for production.

commie1 · 19th Mar 2021, 9:58 pm

Hi Wendy,

Nice job but you have a 150R source degeneration resistor feeding a 2n2222 buffer with an even higher emitter degeneration resistor of 560R, this should be the otherway around.
Next, you have a 78l08 regulator with a 100uF strapped across its output. Since when does one slap a bulky capacitor on the output of a control system?

Wendymott · 20th Mar 2021, 2:37 pm

Hi Commie. Ok about the resistors.. I accept that... the 100 cap is 100 NAN not UFFF.

Just a bit of RF decoupling.

commie1 · 26th Mar 2021, 9:44 pm

Hi Wendy,

Just had a peep at your circuit diagram, it's 22uF not 100uF as originally quoted, my apologies, however 22uF is still a massive capacity to slap on the output of a control system. Actually, TBH many do this, whilst correctly this capacitor should be placed at the voltage regulator input and RC or RLC decoupling should be applied to each stage individually through local RC networks.

Cheers, Commie.

12th Mar 2021, 11:20 pm	#1
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Toko Type inductor test jig Hi Peeps. A few days ago I received a number of Toko Type inductors in the post from Jimbo.. one of our members. However without opening every one.. its difficult to decide what they are good for, so I decided to make a test jig, specifically for Toko 5 pin formers. I already had a fet buffer / impedance match for the Siglent Spectrum analyser / tracking generator , so it was easy to make another with an extra bit to accommodate the coils. As the Siglent's Input impedance is 50 R a high impedance buffer is totally necessary, otherwise the tuned circuit is severely damped. A trimmer cap of 6 - 25 pf is added to see what the tuning range could be. The Siglent shows a 30 Mhz tuned inductor, obviously with a little bit of work to make adaptors any coil can be tested. Another.. unwasted day Attached Thumbnails __________________ Should get out more. Regards Wendy G8BZY

13th Mar 2021, 8:57 am	#2
Electronpusher0 Nonode Join Date: Jun 2016 Location: Bognor Regis, West Sussex, UK. Posts: 2,296	Re: Toko Type inductor test jig I love the way you have made a proper test jig in a box with a printed front panel. I think most of us would have just lashed something together on the bench. Peter

13th Mar 2021, 10:16 am	#3
vinrads Dekatron Join Date: Feb 2009 Location: Chesterfield, Derbyshire, UK. Posts: 3,759	Re: Toko Type inductor test jig Very impressive , love it . Mick.

13th Mar 2021, 10:38 am	#4
CambridgeWorks Nonode Join Date: Jun 2010 Location: Spalding, Peterborough, Cambridgeshire, UK. Posts: 2,858	Re: Toko Type inductor test jig Very neat indeed. With a few coils to test now and maybe even more in the future it saves also the frustration of say miniature croc clips, push on connectors or soldered wires coming adrift. Especially if these are not noticed immediately, leading to head scratching as to why a coil isn't testing as expected. Back in the 70s, I made a "handheld" (10" x 5" x 1.75") 2M transceiver all on one dalo printed and etched pcb. I had obtained a load of reject Toko coils from a scrapyard just outside Skegness. Rank, Bush Murphy I believe it was had a factory in Skegness. Using a gdo, I managed to use some for the 8MHx osc, 24MHz tripler stages, plus the usual IF. I think I may still have a few somewhere. I believe the reason for reject was they had been put in the wrong position, so discarded and a new one fitted. Your test box would have been a handy item for me then! Rob __________________ Apprehension creeping like a tube train up your spine - Cymbaline. Film More soundtrack - Pink Floyd

13th Mar 2021, 11:40 am	#5
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Type inductor test jig Thanks Mick, Peter and Rob. I am very fortunate to have the time..... my personal "no no" is "dead bug".... ok for trial and test but not as a final item. There are a lot of good constructors on this forum . I was brought up on the "if it looks Right" philosophy..... I spent a lot of my working life making prototypes and Test jigs for production. __________________ Should get out more. Regards Wendy G8BZY

19th Mar 2021, 9:58 pm	#6
commie1 Triode Join Date: Apr 2018 Location: Buckley, Clwyd, Wales, UK. Posts: 32	Re: Toko Type inductor test jig Hi Wendy, Nice job but you have a 150R source degeneration resistor feeding a 2n2222 buffer with an even higher emitter degeneration resistor of 560R, this should be the otherway around. Next, you have a 78l08 regulator with a 100uF strapped across its output. Since when does one slap a bulky capacitor on the output of a control system?

20th Mar 2021, 2:37 pm	#7
Wendymott Octode Join Date: Jun 2013 Location: Huddersfield, West Yorkshire, UK. Posts: 1,795	Re: Toko Type inductor test jig Hi Commie. Ok about the resistors.. I accept that... the 100 cap is 100 NAN not UFFF. Just a bit of RF decoupling. __________________ Should get out more. Regards Wendy G8BZY

26th Mar 2021, 9:44 pm	#8
commie1 Triode Join Date: Apr 2018 Location: Buckley, Clwyd, Wales, UK. Posts: 32	Re: Toko Type inductor test jig Hi Wendy, Just had a peep at your circuit diagram, it's 22uF not 100uF as originally quoted, my apologies, however 22uF is still a massive capacity to slap on the output of a control system. Actually, TBH many do this, whilst correctly this capacitor should be placed at the voltage regulator input and RC or RLC decoupling should be applied to each stage individually through local RC networks. Cheers, Commie.