Thanks Rob, that was useful
So a little more digging around and a bit of head scratching leads me to this logic
It's a 6 volt horn. Therefore I need a capacitor that is good for a few more volts than that since the "draw" is fairly large. 50 volts DC would be a reasonable way to start.
The capacitor is there just to prevent the points (on the vibrator) from arcing - and burning out or worse welding shut, this also tells me that using a resister will work in the same way
Given that the horn had a cap to start with that's what I'll put back finding an original wax paper one is proving very difficult been conversing via email to a guy in the US who thinks he has some but; his last mail said "give me a month or two" so I'm going to buy some modern equivalents to play with
Capacitor .5 micro-farad 50vdc. seems the logical place to start
or
Resister 3 ohm
My method will be
HONK the horn for say 10 seconds.... Then do it again a few more times... watching for a spark at the points. There shouldn't be one (or at least not very prominent.) checking the capacitor to see if it gets warm. If ANY heat build up then go with a slightly larger size, have just ordered a selection box for £8
At least I should be able to get it working while waiting for original components to show up
And I thought this was going to be a 1/2 hour job
