CRF's Only Forums

The often quoted mystery box mentioned in the workshop manual.
Often worth hundreds of dollars.

Here is a simple diagram of one that works for those that can read a circuit diagram.
Would recommend a higher voltage capacitor but I was only proving signal from the trigger in flywheel so only a few volts.



Input on left and meter plugs in on right.
I used alligator clips to go on bike and separate banana plugs for my digital volt meter to measure the resultant DC voltage.
Don't be cheap and buy the 4 diodes and make a full wave model.

The push button is there to discharge the circuit so you won't get back EMF when you move the leads.
Can hurt or sit you on your a$$ when testing the coil input.

Hope this helps someone fault finding

Excellent information and post Ray!!!
That can be very helpful trouble shooting nearly any bike.

Thanks for sharing the information and great electrical schematic.

Yep a useful bit of kit when the pesky gremlins get in the electrics.
I found this circuit years ago on the web and built both versions.
Has to be used with a high impedance meter which most DVMs are nowadays.

When testing the low votage outputs like the trigger in the flywheel I found a meter with a capture function to be better as you are only talking around a volt.

Great for primary side of coils though.

Excellent Ray and if you don't mind I am going to pass it on to a Triumph site I am part of. Many of the guys there can use it.

Just add a clause saying that you need to spin the motor over a bit to get the peak voltage. You have to charge the capacitor first till it obtains peak figures.

Like anything British electrics that don't want to, along with an oil drip.
You got to love em.
I am an original Mini driver as well so Triumphs are definitely a nostalgia thing as well.