As part of the research for the NZ Vintage Radio Project I'm working my way through all the old R&E's I have and can get my hands on - I stumble across interesting articles all the time, and this one seemed like it might be quite useful (at least for me) since I've meant to make myself a small winder for years now... so I've scanned it and shared it here in the hopes that it might also be useful to others. Given the Pacific set I posted about a while back has a rats-nest coil that I'll have to do something with I may need to make use of this information sooner rather than later...
Thanks John, I may well need it - here is the aerial coil that has unwound itself...
Interestingly one of the schematics I saw for this chassis has a note from (I think) John Stokes, noting that these coils needed to be wax dipped or they turn from basket weaves to basket cases... nobody got that memo on this set...
I've fixed the link to the document... sorry, it was linked to the old location while I was redeveloping the site. Should work fine now.
Thanks for that posting Steve - I built myself a primitive winder years ago for rewinding output speaker transformers - consisted of a Stanley 'egg beater' hand drill mounted on a wooden frame with a bolt that held the bobbin held in the chuck. You wound by hand and guided with the other hand (actually used a folded piece of wax paper as you could get burns from the bare wires. Good side was it was simple and worked well (used ptfe plumbers tape between layers) BUT any distraction was fatal. This article shows me an entire new level of possibilities.
Hi Steve, I am in the process of building a wax bath for dipping coils. I have a source of bee's wax and at the moment, use a tin immersed in hot water. It works fine but takes a while. The new unit should be much faster. Cheers, John
John, have you considered doing the wax bath in conjunction with a vacuum chamber of some sort? I understand (purely from what I've read, not experience) that the vacuum (or releasing the vacuum) forces the wax in deeper and makes the transformer more stable... Although I'd love to learn a little more about this. Actually I'd love to learn a lot more about coil and transformer winding. I'm still planning to (one day) build a microcontroller based winder so I can accurately control the lay of the wire without finger intervention... but the problem seems to be finding a cost-effective source of copper these days... gosh its expensive. I have quite a bit of vintage enameled wire, but I understand the insulation techniques were not fabulous back then and I'm better to not use it.
There are no personal problems that can't be solved with the liberal application of high explosives
While thumbing through some old copies of "Radiotranics", the AWV technical publication, I found the original article by E Watkinson, a senior engineer at Amalgamated Wireless Valve Co. circuit development group. Its in Radiotronics No. 146, December 1950 for those playing along at home... (bonus points if you get that reference )
That issue also has an interesting (if not slightly over my head in places) article on the design of push-pull outputs and driver stages.