Tug---Kenny
I have juat done what you advised. Powered up 6v and the speaker gave a strained noise twice. Touching the phono plug did nothing. So I assumed it was under powered and tried 12v and I think with a better speaker I will get the sound of a horn its nearly there now with the old speaker.
Bluebird
The two pots do adjust the volume and tone. If I move the stick on my transmiter left it operates also moveing it right operates it. there is a 16 pin chip that the number has been painted out and a 8 pin chip with the numbers 12F629 l/PO5E 0420 printed on.
mrlownotes
I have followed your instructions and got 3 horns. Have selected one which I hope improves when I get the new speaker. If you do have some origional instructions I would be interested.
Thanks to everybody for your help.