Early crystal receiver

[AlanBeckett]

Wonderful Peter, although probably not very popular with the Neighbours these days.

Alan

[peter scott]

Wonderful Peter, although probably not very popular with the Neighbours these days.

Alan

Just so Alan! Although they've probably all got power line wifi extenders and never listen to medium/long waves.

Peter

[Nick]

Clockmakers use something called Horogrene - see http://www.m-p.co.uk/muk/parts/chap10/mp...012515.htm

I've used it - excellent stuff...

[Brianc]

This must not be confused with Horolene which is an ammonia based cleaning fluid which turns brass a pinky colour if used in excess - dezincification!

[unrealdave]

Well I’ve cleaned up the coil terminals using vinegar, wire wool and a little wire brush with brass wires for the delicate bits!

The coil now reads fine so I tried it out with a germanium diode and high impedance headphones and picked up one station nice and clear.  The only difference moving the primary coil in and out made was the loudness – as you’d expect louder when fully in the secondary coil.  I put an old variable air spaced cap across the coil and suddenly could get two stations nice and clear by adjusting the secondary coil with the cap.

Moving the primary coil out I could hear a third station over one of the others.

Now the detector and other bits on the centre panel.  I cleaned the aluminium detector body with a metal polish and a toothbrush as vinegar makes aluminium go black.  The rest of it I took to my mates as the rubber covering on the wire was perished and anyway I couldn’t make the circuit out.  Still can’t completely.  What I am going to do is take it apart bit by bit and clean it then put it back then take some more off and do that.  This is so I don’t muck up putting it back together.

From what I can see there is a transformer with three connections next to the detector and another coil underneath at the centre.  The switch puts either the buzzer in circuit with the detector so you can hear when the spike is at maximum sensitivity.  There are terminals for a bias battery, a terminal marked K that connects to one end of the secondary coil and one marked J that must then go off to the headphones then back to the other terminal on the coil.  (bit off guess work there)
 
This is interesting
http://www.americanradiohistory.com/Archive-Radio-News/20s/Radio-News-1928-02-R.pdf
 

Alternatively, Helen has suggested that the Royal Signals Museum might have an answer http://www.royalsignalsmuseum.co.uk/

That's a great idea terry and I have emailed them to see if they have any info