Homemade Denco Coils

[Backtoreality]

Hi everyone, I just wanted to say thanks to Jim Jobe who gave me the data to make my own Denco type coils and to show you the finished articles so far. The coils are all Green type and Range 5,4 and 3 left to right in the photo. For the first two I've used Damart pens (free to good customers I think) and the third is made from a Staples Comfort Stic (only £1.79 a dozen) The Damart barrels are wide enough to take a 1/4UNF dust core on the end of a 6BA screw without catching but I was really pleased to find the Comfort Stic is just the right size to tap with a 1/4UNF thread, so I can finally use my free 1980 Practical Wireless core adjusting tool. The base of the first coil is quite rough but for the next two I found a plastic cap to use as a mould for the epoxy putty. Cling film stopped the putty sticking and pressing a B9A valve into the putty gave me the guide for the 20swg pins. The barrels were then forced into a 6mm hole enlarged slightly with a file and finally the pins and barrell were glued in place with dabs of epoxy resin. I did originally try removing the valve base from an EY86 valve but just when I thought I'd managed it the wire snapped off pin 9 so there was nothing to solder the coil to. All I need to do now is build a radio in which to test them! EF50's where are you!

[Herald1360]

I've got a NIB VR91 you can have for a couple of quid plus postage.......

[dominicbeesley]

Good effort! Where did you find the information on turns etc?

D

[Backtoreality]

I did a Google search and it came up with a posting on this website from Jim Jobe about 7 years ago saying he had worked out the coil info for ranges 3, 4 and 5. I emailed him and he came up trumps!

[dominicbeesley]

It would be worth posting it up here for reference if you and Jim don't mind...There's been a few times I've needed to make up a coil and had to mess around guestimating...

[jim_jobe]

The data is attached: I'm not sure why I didn't do this originally.
Great effort David (far neater than mine!) Let us know how they work in circuit.
Jim

[Anthony Thomas]

Nice work on making those coil formers

Years back I obtained some formers from Isoplethics but never wound any coils on them, I have some B9a and Octal formers that were reasonably priced I thought at the time.

A Google search found this but no web site, I had to write last time:
http://www.valve.demon.co.uk/supplies/isopleth.htm

Hope this helps.
Tony

[Anthony Thomas]

I managed to purchase some B9a plugs that could form the basis for plug in coils, I think that J Birkett used to have such items in stock for a reasonable price. B7g and B9a. Octal also maybe.

Tony

[Backtoreality]

Originally Posted by Herald1360

I've got a NIB VR91 you can have for a couple of quid plus postage.......

Thanks for the offer, I have a couple of VR91s already which I bought in the 1970's for 50p each (they were marked up as 10/- and they converted the price!) I also have a black EF54 in reserve but if they are dead I may be coming back to you!

Originally Posted by jim_jobe

The data is attached: I'm not sure why I didn't do this originally

Thanks everyone for the encouragement. I've had great fun making the coils and I'm still at it now. Worryingly I can't look at a pen without thinking how suitable it might be to turn into a coil former! I'm not quite sure about the differences between the yellow and red coils though Jim and I have a nasty feeling that I'm going to have to have a go at making a set or two of them for a superhet although I will probably have to buy an old Perdio radio to get the Denco IFts!
David

[jim_jobe]

Originally Posted by Backtoreality

I'm not quite sure about the differences between the yellow and red coils though Jim

The main winding is the same for both yellow and red coils, David, but the red also has a winding for the aerial coupling between pins 8 and 9; the yellow coil having just a coupling coil between pins 5 and 7.
Jim

[RF Burn]

It may be possible to modify B9A socket savers to make bases for these coils:

http://www.ebay.co.uk/itm/2211399659...%3AMEBIDX%3AIT

Adrian

[Backtoreality]

Thanks Adrian, I wish I'd seen these before! Having said that I have had a lot of fun!

[jim_jobe]

Mea culpa!!! In post 11 I shpuld have said blue and yellow coils NOT red and yellow!!!
Jim