Hi JonE

I have had a look at all the pictures you posted. The Hitachi 2SC282 is a Silicon NPN switching transistor. The Sanyo SG005 is a medium power rectifier diode. The stripy things are resistors and the green things are capacitors. There are also a couple of smaller diodes. So you have a one-transistor circuit.

I an 99% certain that the two screwdriver adjustments are preset variable resistors. Since the blue wire connects to one of them, I suspect that the green wire connects to the other. You might like to check this as I can't tell from the photos. If this is the case, I am wondering if one wire is for 4 cylinders and the other one is for 6 - you just connect whichever is appropriate to the breaker points and ignore the other. The variable resistors allow separate calibration for the 4 and 6 cylinder modes. Maybe this setup was cheaper or smaller than providing a switch or links ?

The insulated studs are for the battery positive and negative. I suggest you try it out with the three connections, experimenting with blue or green to the contact breaker and trying the effect of tweaking the relevant variable resistor.

Cheers, John C.

Location: New Forest

great, thanks John. Will report back.
I think you are right that the green goes to the other variator.

What is interesting is that that blue wire is short, and on BOTH my unit and that of the chap on the Commer forum it appears to have been connected to the negative post (i.e. one didnt even see it when in it's cowl)

Not sure if this helps...

I have a Crypton revcounter on a Morris Minor sidevalve and the back has 4 terminals, earth, signal and 2 terminals that are bridged with a small strip of copper. The instructions state that you remove the bridge to turn it from 4 to 6 cylinders.

Location: Cardiff