Transformers, Coils, Chokes

[Geaney]

In hunting around for a mains transformer for my Eico 950A I came across these folks in Sweden:

http://www.lundahl.se/sidor/other_tubeOPTb.html

They seem to have one that fits the bill for the Eico.

Their direct order process seems a bit laborious (and apparently only available if there is no local distributor) but I've sent off an enquiry and I'll let you know how it goes....

Cheers,

John

[Retired]

Hi,

Thanks for adding the link John.

When I started as a complete novice over ten years ago trying to restore vintage radios I quickly learned that a coil winder and valve tester were necessary bits of kit.

With the AVO Mk1 VCM I could test valves and replace as needed. The coil winder was an AVO Douglas hand winder and this proved invaluable saving me lots of hassle in trying to find replacement transformers/coils etc.

I made rapid progress with the winder as I could wind to my own specifications; when the primary of a radio mains transformer failed I simply rewound but only for 240V as this saved playing around with unnecessary tapping.

Having progressed with the winder and learning transformer basics I then successfully installed three phase into our garage at very little cost .

Kind regards, Col.

[Geaney]

Hi Col,

I've got hold of the drawings for building a coil winder so it's on my to-do list. However once I have a working one I'll start out with 'simple' coils before tackling more complex items like transformers. The road ahead is long in terms of building the skills - but that's part of the attraction!

Cheers,

John

[Retired]

Hi,

If you've never wound a coil before John may I recommend you try to obtain a copy of "Wireless Coils, Chokes and Transformers" by the author F.J.Camm?

This is only a small book but even I quickly grasped transformer basics with ease after reading the few pages on the subject.

Good luck.

Kind regards, Col.

[Skywave]

Winding coils, etc.: another useful book is 'Coil Design and Construction Manual', Bernard's Radio Manuals #160. My copy is quite an old publication and I know that an (updated ?) equivalent was also published by the Babini Press. They are well-written and useful.
Occasionally, I've seen both advertised for sale on e-bay.

Al.

[Yorkie]

Interesting hand coil winder with built-in counter and two-speed gearing here. (New, 'buy it now'):

http://www.ebay.co.uk/itm/Manual-Coil-Wi...uipment_ET&hash=item43b8eedfde

This one is mains powered, CNC controlled, and appears to give lateral tracking options as well as turns counting and variable speeds. Keen price - shame about the shipping costs (unless we live in Hong Kong!):

http://www.ebay.co.uk/itm/AUTOMATIC-COMP...ltDomain_3&hash=item417169046d

[AlanBeckett]

David,

I've seen the Manual one before and wondered if it would be a good starting point for 'improvements'.
I don't think I fancy the outlay for the 'Digital' one.

Alan

[Andy M0FYA]

Interesting hand coil winder with built-in counter and two-speed gearing here. (New, 'buy it now'):

http://www.ebay.co.uk/itm/Manual-Coil-Wi...uipment_ET&hash=item43b8eedfde

David, I bought one of those hand-wound winders perhaps 18 months ago. A total waste of money, it is junk! The castings are so crude, including the gears, which wobble as they turn. I can only conclude they were fettled by someone crouching in the dirt, holding them between their feet.
I'll not say any more or you will think I am exaggerating.

Andy

[Yorkie]

My thoughts too Alan.

Apart from the winder that John posted the link to, which showed the American Antique Radio Society video of rewinding field coils for mains energised speakers, I haven't seen a homebrew design which will traverse the turns back and forth at the correct rate for the gauge of wire being used. They all seem to rely upon running the wire through fingers as best one can, the effect being a scramble wound coil. No doubt coils made in such a manner will work OK, but a winder that will lay the turns neatly side by side is what's really called for. What surprised me about the US one was how 'clunky' the rack and pinion traversing arrangement was, with its coarse teeth pitch, though it seemed to work fine. Obviously the two variables which need to be adjustable as the width of the coil, and the turns per inch (cm, or whatever) according to the gauge of wire.

I thought that the manual one was reasonably priced but couldn't make my mind up whether it was all plastic. Seemed a bit too cheap to be metal. P&P on the other one was the killer punch!

A lot of people on youtube seemd to have twigged onto using a cheap calculator as a turns counter - sometimes using a cam to press the = button with each turn of the coil, others, which wire a microswitch or magnetic reed switch across the calculator contactss, as I did on my hand winder.

[pwdrive]

Would this one be any good?

http://www.youtube.com/watch?v=a3w85Y2DS1g

Lawrence.