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Hints, Tips and Solutions (Do NOT post requests for help here) If you have any useful general hints and tips for vintage technology repair and restoration, please share them here. PLEASE DO NOT POST REQUESTS FOR HELP HERE!

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Old 13th Dec 2010, 6:32 pm   #1
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Default Coil winders.-

Hi,

Here are a few notes for members unfamiliar with coil winders. I have four coil winders including one AVO Douglas hand winder; two German Aumann electric winders and an AVO Wave winder.

Whilst I had my Aumann winder set up I thought it might be of interest if I took pictures and added them to the forum together with a few details.

Both my Aumann winders are of the same type being foot speed controlled bench models. New they would have been expensive machines to buy. They are very well made and heavy. Speed is fully variable via the foot control; with the empty bobbin and wire set up the digital counter is adjusted for turns required; in the case of this rewind 2,350 on the upper row of thumb wheels and the bottom row are left at zero.

With everything set up ready for winding and the wire gauge adjusted with a simple turn of a dial the foot control is pressed firmly with the heel until a click is heard then the control is rocked gently forward to bring on speed. Wire is run onto the bobbin until the desired width of winding is reached then the automatic stop is set; this stop triggers the carriage to traverse in the opposite direction; as the opposite desired width of winding is run on the second automatic stop is set. Now it is a simple job to run layers of wire on adding insulation as required between layers; the carriage lays on the wire very precisely and the carriage change of direction has to be seen to be believed; just a click at each end of the winding as it changes direction; the carriage can be reversed by simply pressing a button on the front control panel making winding incredibly simple. The winder stops automatically once the preset counter number is reached.

It was interesting for me to see the rapid bobbin change mounting on one of the winders obviously set up for repetition windings of a single bobbin size; the bobbin is simply slid into position being held in place by a spring clip clearly seen in the picture. Not owning the correct wire feeder I place the bobbin containing the new enamelled wire on the workshop floor and easily control tension by hand; adding just enough tension to lay the wire neatly without stretching it.

Although I have two of these Aumann winders I have only a single foot control and after taking the pictures the winder refused to work; I played around for an hour or so before pulling the second Aumann winder out to find this had come out in sympathy also refusing to work indicating a possible foot control fault.

It’s too cold to play around in the workshop so I completed this rewind using my AVO hand winder but for pure pleasure these Aumann winders take some beating.

A few months ago whilst at “Winding Technology” I was offered a very large electric winding machine very cheaply indeed; this machine accepted eight bobbins of enamelled winding wire and could wind up to eight separate windings simultaneously automatically adding paper interleave insulation. Once the windings were completed they were separated by knives cutting through the paper. I declined this winder on the grounds of its footprint and not having enough work to justify buying eight large bobbins of enamelled wire but it was an absolute bargain at the price.

I’m self taught at winding but find it engrossing and once the basics are grasped the process is easy. I’ve wound IF transformers; O/P transformers; Mains transformers and many smoothing coils. Whilst learning to wind I’ve made just about every mistake possible from having coils collapse to not understanding what a centre tap is. I now add Tufnol flanges to transformer bobbins if the bobbin has not already got them fitted.

My first radio mains transformer rewind was for my Murphy A30C. I’ve forgotten the exact details but I did the calculations and wound the transformer only to find it gave exactly half the expected voltage on the rectifier; if the rectifier needed a balanced 350V I wound for 350V adding the centre tap not realizing the centre tap actually split the voltage giving 2x175V. I rewound the transformer for 700V and now it gave the required 2x350V with the centre tap added. A simple mistake but one that took a lot of head scratching to solve.

It took a while but another simple trick I picked up was how to determine the turn’s ratio of a mains transformer; I found that if the heater winding was for 6V then I could easily identify this winding and mark the tails; the heater winding is wound with heavy gauge wire and not many turns are used. It is simple to count the turns and if say I counted 30 turns then the transformer turns ratio is 5 to 1 enabling all the other windings to be calculated; take for example the primary on 240V; multiply by 5 and the primary winding has 1,200 turns. For multiple voltages between 200v and 240V then tails can be added as required.

Winding wire is expensive and rewinding a transformer is very time consuming so to get a transformer rewound professionally is bound to cost a lot of money and in my opinion this is justified.

I enjoy transformer winding but am not set up permanently for it as I have to keep pulling my winder out then putting it away after use making it rather a chore as setting up takes longer than the actual winding.

These notes are very basic and members such as Ed Dinning can run rings round me when it comes to transformer technology and winding but by trial and error I can now rewind all the usual transformers and coils found on my vintage radios. My book entitled “Wireless Coils, Chokes and transformers” by the author F.J.Camm gave me enough easy to understand information in just a few pages to attempt my first transformer and as the book is written with a complete novice in mind I soon picked up the method.

I hope my ramble is of interest.

Kind regards, Col.
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Old 13th Dec 2010, 7:13 pm   #2
AlanBeckett
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Default Re: Coil winders.-

Col,
A splendid write-up.
I have a copy of that book, 5th edition 1941, but sadly no winder yet. Fear not, I'll be round at the weekend with my duff output transformer
Alan
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Old 13th Dec 2010, 8:20 pm   #3
Aerodyne
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Default Re: Coil winders.-

Looks as though you may have opened the doors to many rewind requests, Col. As always, a great topic and a very lucid and entertaining write-up. Good photos, too.
-Tony
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Old 13th Dec 2010, 8:26 pm   #4
Sean Williams
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Default Re: Coil winders.-

Hmm, my workshop appears incomplete - I need one of those coil winders!

They look like a superb bit of kit!
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Old 13th Dec 2010, 9:56 pm   #5
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Default Re: Coil winders.-

Hi,

You’re welcome anytime Alan.

Thanks Tony for your kind comments. Indeed I receive many requests not only for transformer work but also cabinetwork which I have to sadly decline. Radio and now TV is just a hobby for me and I don’t have enough time to complete my own projects; being retired takes up a lot of time. I’m also getting the hang of using Gimp 2 as I used Gimp to make the pictures clearer.

Yes Sean these winders are a great bit of kit and I can highly recommend them; if ever the weather warms up I hope to play around with them a lot more because I’ve owned them for over a year and this is the first time I’ve tried them out.

I was pleased to finally rewind the Bush SUG 43 O/P transformer as it has been driving me mad for over two weeks because it has been too cold to get into the workshop; I’ve kept having a go at it and now the tails just need connecting then I can fire it up knowing it has now got continuity through the primary.

The pictures show this transformer as work in progress. The transformer was very rusty and looked a mess; the outer insulation was removed then the bobbin was mounted on the AVO Douglas winder and as the handle was turned with one hand the other hand guided the old wire onto the workshop floor whilst turns were counted; this took quite a while to accomplish but ensured I could rewind like for like; the outer secondary yielded 59 turns and 2,350 turns later the primary was removed. This gives a turn’s ratio of 40/1 (Near enough).

Tufnol flanges were then cut out and added to the bare bobbin securing with best “Poundland” epoxy adhesive. This bobbin has a rectangular hole so care was needed to ensure the bobbin would actually fit into the laminations once the new flanges were fitted. The laminations were accurately measured where they fit over the bobbin to determine the depth of the flanges; these being the inner measurements as the laminations would actually cover the flanges once assembled and to make the depth too deep the laminations would not fit (window depth). The other two narrow sections had 1/8” added to the depth as a precaution due to extra thickness of the winding with tails added; these tails must be added to the outer sections of the flanges not covered by the laminations but once the mistake has been made of adding them in the wrong place the same mistake won’t be repeated. To fit the flanges the outer edges of the holes were filed neatly to about 45 degrees forming a chamfer; the flanges were then pushed into the centre of the bobbin and epoxy added to the outer ends now when the flanges were pulled out to the ends and aligned the flange pulled with it excess epoxy and due to the chamfer previously added made a stronger joint; once the epoxy had set excess was cut away with a sharp wood chisel.

The bobbin was then mounted onto the winder and the primary was run on adding yellow transformer insulating tape every second layer; with the primary completed it was well insulated then the secondary was run on and again this was well insulated completing the actual winding. Tails having been added.

The laminations were then inserted and the outer frame added and secured leaving just the four tails to connect up. It certainly looks a lot better for a bit of TLC.

Once I get this Bush chassis off the bench I can make a start on the Ekco T311 TV.

Kind regards, Col.
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