I am attempting to repair a set with a Ferrotune permeability tuner. Inside the badly corroded unit, in addition to the expected two tuned coils and their associated capacitors there is another component encapsulated in some form of wax. I have identified three wires coming out of the unit, all multi strand and extremely fine but I suspect there are more as one has no connection to the other two and the two that have some connection have no meaningful inductance. All these wires have been severely corroded such that I have no idea where they connect to.


Does anyone have any information on the internals of the Ferrotune unit? or a spare they would be willing to part with.

Joe

Is this the tuner in your radio?

https://www.radiomuseum.org/r/kingsley_ferrotune_tuning_unit_kfjb.html

The RM schematic shows the tuner as a 'black box'.

There's a construction article for the model KFT1 on Kevin Chant's site, here:
https://www.kevinchant.com/uploads/7/1/0/8/7108231/kingsley_ferrotune.pdf

If nobody else comes back with the information, I can trawl through my library of magazines for articles on it that may be useful.

Radio and Hobbies published a radio that used that tuner.

Thanks GTC,
That is the unit, from the RM site if you look at the thumb nail pic on the top right of the web page, then you will see a round black blob at the top right of the unit behind what is presumably a white mica capacitor, that's the bit I am track down. My guess is that it is an coil (or maybe two) probably in series with the variable coils but I can't be sure.

I have checked all the usual places and some not so usual but although there were four versions of circuits published for it (including Radio & Hobbies - thanks Marc) there does not appear to anything on the internals other than dire warning that if the external shield was breached you'd never be able to get it to work again - no user servicable parts inside.

These tuners were typically sold as a kit for home builders (complete with chassis, tuner and IF coils) however the set on the bench is a manufactured item, so it seems rather unusual - I have mentioned it here before - it's an electro-voice, wooden mantle - which is why I wasting so much time on it.

I can't seem to make much sense of the measured L and C's so I am hoping someone can provide a few clues before I relegate this to the "too hard basket"

Joe

It could be a coil. I have tried to search for the alleged Aus and US patents with no success. The description accompanying a patent application can sometimes give a clue to such things.

I have sent a schematic

I have sent a schematic

You have a schematic that diagrams the internals of the Ferrotune unit?

Actually no, Carl unfortunately does not have a schematic on the internals, but I give him full marks for trying, the radio schematic he sent me is the very first published, there were a few more variations that followed and the radio on the bench is slightly different to anything published but nothing insurmountable.

And thanks GTC I went the patent route but like you turned up nothing, seems a real shame as this radio is a unique bit of Australian radio history that is likely to end up in the rubbish bin. Still keeping fingers crossed that someone has a unit that they can explore and measure and even better part with.

Joe

likely to end up in the rubbish bin.

I'd hang onto it. Another chassis may come up and one or the other can be a parts donor.

I'm puzzled about the patent. I can find plenty of patents granted to AWA for permeability tuners in the 1940s, but absolutely zilch on the Kinglsey (Love) unit -- and I used every imaginable search term and search field, with and without wildcards. Also, the patent number stamped on the one in the picture was assigned to other unrelated patents throughout the years but I could not find it used for this unit. Very odd. Love does not strike me as the sort of guy who would put a bogus number on his stuff. I may have missed something, but I don't usually have such a problem finding stuff in the patent databases.

I assume you found this:

http://messui.polygonal-moogle.com/valves/NW199408.pdf

Maybe a few clues in it.

^ Yes, I had read both parts of that very interesting article by Nevile Williams. It describes what a great entrepreneur Love was, but doesn't lead me any closer to the details of the internals of a Ferrotune unit.

Ferrite tuners were very common in car radios and a swine if a coil went open. The Chrysler Valiant actually had a ferrite slug & bobbin on the the throttle.

Basically instead of changing "C" you are changing "L".

Ferrite tuners were very common in car radios

... and crystal sets in the 1960s. For some years, I've been trying to find the same model that I was given for my birthday in 1964 (purchased from Hobbyco in George St), in order to complete my collection of radios that I experienced in my earlier years.

Ferrite tuner is not the nomenclature used that's probably an issue? Its called "Permeability tuning".

I have worked on run of the mill valve radios with it.

https://electronics.stackexchange.com/questions/70260/what-advantages-to-permeability-tuning-as-against-capacitive-tuning

Its called "Permeability tuning".

Yep, see post #9.

Ferrotune, etc, would qualify as a trademark, although Love doesn't seem to have registered those names.