Yes
Armature is shorted to ground.
It’s possible you might be able to inspect it carefully and find a wire shorted that could be lifted away and paper put underneath and sprayed with insulating enamel.

Alternatively you might be able to find which slot or commutator segment the winding is shorted in and cut that coil out of the armature circuit

i tried on a number of segments and they all showed a voltage.....the other thing i noticed was it had some bad grooves in it.....the annoying thing is it was a reconditioned dynamo no more than 50hrs ago (out of warranty now)

Right, so an update. I got another dynamo and put on, before i did it i bench tested to see what voltage and it showed 4.8v with the cordless wrench driving it.

So I have installed it and started up. On tickover it was showing 27.1 volts, then full speed was 32 volts!!!....blowing the doors off!
I put on another voltage regulator i had in stock (or unknown condition) - the result was the same, but on tickover it went to 26.8 volts and the ammeter was actually showing a minus amperage, not sitting on zero.


Any clues what is going wrong here?.....like there's no cut-out control

thanks

You could still have regulator problems. Seems like the first regulator just needs adjusting down a little

First disconnect the field wire from the regulator and see what your voltage on the GEN/ARM terminal is at engine high idle. If just the small residual voltage on the GEN or ARM terminal, reconnect the field wire and adjust the voltage inside the regulator. It can be a tedious process to get the spring tension adjusted to get 28-29 volts on fully charged batteries. Should be able to find a diagram showing which spring to change the tension on.

I've just tested it, there's between 2.5v and 6.5v coming up the field wire depending on engine speed.
Also I measured about 10 amps coming out of the generator.

Honestly i don't see what i can adjust in the regulator. I took the cap off to see if i could see the points moving, I discovered that the cut-off coil is permanently engaged, if i prise it off with the screwdriver the voltage drops to something sensible. I altered the gap (reduced it) and it didn't make any difference.

On the voltage coil i held that in the opposite direction and the voltage went off the scale.

I was doing a bit of reading and saw mention that the cutoff coil is also supposed to stop the battery draining. When i shut the engine back to tickover the ammeter goes in the red, as if there's a significant drain

The adjustment is spring tension on the springs along the back of the arms. There used to be regulators with tiny screws to change the spring tension, but anymore they’re all set by bending the anchor point for the spring up or down slightly

On the cutout relay you will want to increase spring tension to pull the points open against a higher voltage/higher current running through the coil. When the current reverses and begins flowing INTO the generator, the magnetic field should collapse and allow the spring to open the points.

OK, thanks....i did just try it now before packing up for the day, put (what i thought) was quite a bit of tension on the spring and it didn't seem to make any difference.

I will have another look tomorrow

thanks once again for your help on this!

Hi Team,
do not profess to be any expert but I am aware and have encountered a B Regulator on an A Generator and had issues but was way back in the mid 60's--hazily it seems the issue was similar to your experience.

If you go down to pages 9 & 10 in the PDF below it should explain better than I about this.

It goes without saying that not all generators and regulators will mix and match as they need to be of the same wiring family--designated as A or B-- for either Internal or External Grounding of the Field Coils and so a specific regulator is needed for each application.

I stand to be corrected.

www.venselenterprises.com/techtipsfromdick_files/generators.pdf

Cheers,
Eddie B.

"edb" wrote:

Hi Team,
do not profess to be any expert but I am aware and have encountered a B Regulator on an A Generator and had issues but was way back in the mid 60's--hazily it seems the issue was similar to your experience.

If you go down to pages 9 & 10 in the PDF below it should explain better than I about this.

It goes without saying that not all generators and regulators will mix and match as they need to be of the same wiring family--designated as A or B-- for either Internal or External Grounding of the Field Coils and so a specific regulator is needed for each application.

I stand to be corrected.

www.venselenterprises.com/techtipsfromdick_files/generators.pdf

Cheers,
Eddie B.

Eddie,

thank-you very much for this information

I'll have a study of it

Richard