An interesting old Coil

[AlanBeckett]

I'm following your other Thread with interest. I briefly thought it might be a Signal Generator or a Wave Meter but probably not.

Alan

[pwdrive]

I'm following your other Thread with interest. I briefly thought it might be a Signal Generator or a Wave Meter but probably not.

Alan

Cheers Alan, I'm following the same on your coils thread for sure, you're doing a good job with the research/ID, pictures, diagrams and descriptions, all very clear and to the point, plus hopefully if the internet lasts it will be an historical record covering a particular aspect of early vintage receivers that very little seems to be known about these days.

Lawrence.

[AlanBeckett]

Thanks Lawrence. My guess wasn't too bad apart from the 'Other' Front Terminal which I thought was an alternative Aerial but was actually the Earth.
What a Charles not thinking of that

Alan

[AlanBeckett]

Last lap before Christmas?

I've done a bit more investigations and as far as I can tell it looks like this:-

   

A few Comments:-

The Black 'Spots'  on the Switches represent the Insulated Contacts.

The Switches have no Detents. You have to rely on the Markings and the 'Feel'.

The only Switch Connection that I can positively Identify is the AERIAL Terminal to the Wiper of the APERIODIC SWITCH. Seems logical.

I still don't know what AG means.

The Shaft of the WAVE CHANGE SWITCH is extended at the back. Perhaps there's a Brother to this Coil so you could add an rf Stage.

As far as I can tell the ANODE Terminal isn't directly connected to the REACTION FIXED Terminal. There's a small Resistance but no measurable Inductance. The connecting Wires disappear into the Coils so perhaps the Reaction Winding is split. Without disconnecting Wires, which I'm reluctant to do, I fear there's no way of telling.

So, I suspect the only sensible thing thing to do is believe the Connections as written.

Alan

[pwdrive]

And finally(?) for this year .....

This one came attached to a Home-built Wireless.



As it was all of a couple of Miles from me, and contained some interesting Components apart from the Coil, I decided I might as well bid. I wasn't disappointed and got it for £24.
It contains 4 Valves, one sadly with no Filament, Valveholders, Tuning Capacitor, Reaction Capacitor, Filament Rheostat, Switch, Grid Leak assembly, two LF (Inter-valve) Transformers and the all important Coil. There is also the Case.

It wasn't very easy to examine the Coil in-situ. About all I could make out was the name 'British General'. There are references to the Company on the Radio Museum Website - http://www.radiomuseum.org/dsp_herstelle...y_id=11974  - and even a similar Coil, but not the exact one.

I decided that I'd better try to work out the Connections. The Wiring is pretty shambolic but I came up with this:-



It seemed reasonable but I decided the only sensible thing to do was to remove it for a closer look. The only tricky bit was getting one of the Knobs off. It really was stiff and made me very nervous, but it succumbed to some Penetrating Oil and a bit of persuasion. The Shafts appear to be 3/16" Diameter. I can't say I've come across that size before so perhaps it came with its own Knobs originally. The Coil itself was held to the panel by the Shaft Nuts.

Having got it out and cleaned some muck off all was revealed. Each of the Terminals is helpfully Labelled (Cast) as follows:-

REACTION FIXED
EARTH
REACTION MOVING
ANODE
GRID
AERIAL

Further, there are two 'Feet' cast into one end and mounting it that way up all the Printing on the front is the right way up.



Sorry about the Pictures.

The 'Top' Switch, which is 2 Pole, is labelled WAVE CHANGE SWITCH and L, M, S2 and S1.
The 'Bottom' Switch, which is Single Pole, is labelled APERIODIC SWITCH and L, M, S and AG. I guess that's Aerial Coupling and I haven't a clue what AG might mean.

The Switches themselves are quite crude. The Wipers contact the Heads of Screws. Some of the Screw Heads are 'Insulated' with black material, presumably to produce O/C.

A fascinating gadget which must have cost a fortune in its day.

I'll try to work out the internal Circuit.

Alan

Alan, Ref. AG position:  Antenna to Grid?

Lawrence.

[AlanBeckett]

That's a good Theory, I like it
As before I'm not sure how to prove or disprove it without disconnecting.
I'll have a think.

Alan

[pwdrive]

Just a visual reference from an old listing (British General):

http://www.ebay.co.uk/itm/Vintage-1911-B...SwwbdWJTYu&nma=true&si=P9llJOK%252BabsRg0okHBxZU1tF0zE%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Lawrence.

[AlanBeckett]

Poor old Soul
There's a good picture of the way the Switch works on the Screw Heads.
It's just as well I didn't see that at the time.

Alan

[pwdrive]

Alan, I came across at least one other completed listing on Ebay showing British General coils "similar" to the one shown in post#117, they were undamaged.

You might have already come across them but I'll post them up anyways.

http://www.ebay.co.uk/itm/Vintage-amateu...SwT4lWSblM&nma=true&si=P9llJOK%252BabsRg0okHBxZU1tF0zE%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

http://www.ebay.co.uk/itm/Vintage-Radio-...SwAKxWYy3l&nma=true&si=P9llJOK%252BabsRg0okHBxZU1tF0zE%253D&orig_cvip=true&rt=nc&_trksid=p2047675.l2557

Lawrence.

[AlanBeckett]

I'm afraid I didn't see either of those Lawrence

Alan