My Second Radialva Groom Restore

[Radio Fixer]

There are various ways of configuring the field coil to use as a smoothing choke, as well as provide the electro magnet. Obviously it will be more effective with full wave rectifier circuits where the ripple is 100Hz rather than the 50Hz of half wave, twice the reactance for the same L. In the Ferranti Arcadia the field is in the negative supply rail to provide AF valve bias. It has a potential divider using high value resistors and of course a smoothing or filtering capacitor.

Well David most manufactures couldnt do PM speakers in the 30's but of course the wonderful Philips could. Both my SI sets 1933 and 1934 have PM speakers.

I would beg to differ on the rewinding of field coils being a difficult task. I think, certainly for low resistance (series use) ones, its an easy task and well within the capabilty of most restorers. I used to do it with a a bobbin, sometimes cheeks have to be added, in a battery drill clamped in a vice. The new wire can simply be put on the floor and allowed to spool off the side in fishing reel style. Of course if you had a lathe that could be used although a quick stop might be tricky .

Later on I made a crude but cheap and effective coil winder (see BVWS mags) and that made winding easier. With this I wound one with 40,000 turns and a resistance of over 5K Ohms. Not difficult, and no breaks, just patience and time but Hey! thats all this hobby is: a pastime.

Gary

[pwdrive]

The replies as regarding the field coil have given me more of an insight to the various configurations etc and the techniques used etc. All interesting, thanks.
Hopefully it will help John get his radio fully up and running.

Lawrence.

[Geaney]

Thanks once again chaps for all the great help on this topic. Since my goal with this project is to learn as much as possible and time is not an issue I think I'll take a journey into the world of coil winding. Apart from the field coil issue there are a number of other coils missing from this set so this would seem like a good time to have a go at making some of my own.

All pointers to good write-ups on coil winding much appreciated - while I see about finding/making a coil winder!

Cheers, John

[Radio Fixer]

Hi John

Dont know if you are a BVWS member but there are my writes ups from sometime back on making a winder in the Bulletin. I have done speaker fields and transformers on it. It doesnt traverse the wire in neat layers. Its hand lay for this but the results are fine. Obviously if you need wave wound coils it wont do that.

If not a BVWS member I have the articles as PDF proofs and can e-mail them if you PM me an e-mail.

A guy on the US Antique Radio Forum developed it further and used a simple mechanical turns counter rather than my (over complicated?) electronic one. He was pleased with his result. If you search on there you should be able to see his.

Alternatively someone may have something for sale.

Gary

[Yorkie]

Apologies to anyone who's seen this video of a simple 'wave-winder' before. I know that it has inspired quite a few vintage radio enthusiasts to build one.

I posted pics of mine recently, which just needs the wire feed guide making to be finished. The winder can be cheaply made - I made mine from bits I already had. I just needed to buy the steel washers that are used for the cam and drive. I found that the drive wheel - for which I used an 'O' on a pulley that I turned, slipped on its mating disc, so I glued a disc of 400g wet and dry to the metal disc to give a better grip. I also found that the spiring in the 'tally counter' (the type of thing used to count people back onto a coach to make sure no-one is left behind!) was too strong, and caused the drive spindle to stall, so I had to dismantle the counter (fiddly job) and cut a couple of turns off the spring to weaken it. I only fitted that type of counter to be faithful to the original, but I'll remove it and as I said in another post, instead, I'll use a pocket calculator with a microswitch on the wider spindle, wired across the '=' button on the calculator to increment the turns. Cheap, simple and no resistance on the winder drive mechanism.

The width of the coil is determined by how far the 'cam' (a brass collar soldered off centre to a disc) is set off centre. That pushes the wire guide back and forth to the extent of the offset.

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

Neat eh?

[Geaney]

Don't know if you are a BVWS member but there are my writes ups from sometime back on making a winder in the Bulletin.

Thanks Gary,

I sent off my BVWS application form and cheque a few weeks ago - still waiting to hear back. Hopefully I'll hear from them soon. I'm signed up for the forum so I'll go check it out.

Cheers, John

[AlanBeckett]

What Forum?

Alan

[Mark R]

methinks that is the dark side forum

[AlanBeckett]

Oh dear

Alan

[Yorkie]

methinks that is the dark side forum

Probably.

Now't to do wi' t'BVWS is it, though it's a common misconception that it is.