1940 DH generator problem

[Ken in AZ]

Now that I have the tractor running nicely I'm trying to get the electrical parts working. The generator is giving me fits. This is the generator that is inline between the mag drive and the magneto.

It's got an internal fuse that it keeps blowing. I'm not too sure why but it will do it even with the regulator disconnected. This is a 3 brush type generator and when I jumper across the fuseholder, the generator will put out up to 15 volts with the output disconnected and the engine pitch changes slightly (meaning it's pulling a little power from the engine, I think. not a lot though).

Is there anything to look out for on these things? It seems like a lot of current is going someplace in the generator but I don't know if there is an adjustment or something I'm missing.

A schematic or some notes on how they are supposed to work would be greatly appreciated.

Thanks

Ken in AZ

 

[John Saeli]

What voltage battery you got in there? Sounds to me like someone has converted a 6V Gen to a 12V Gen.

 

[mEl]

A 6V generator unhooked so it has no load may go to a voltage that high as there is nothing to hold the voltage down as it is an unregulated system depending on the battery charge load to hold the voltage down. Is the fuse in the charge line? I have a hard time believing that that system will charge at enough to blow a 15 A fuse. Did you try to change the charge rate by moving the 3rd brush to a lower setting, I believe that genny has a screw on the rear cover to loosen to move the brush. Does it blow immediately or after running a bit? It does sound as if you have a good genny, what does it show on the ammeter before the fuse blows? mEl

 

[Ken in AZ]

Hi mEL,
The generator is the one between the mag drive and magneto on this setup. The DH didn't have electrics but the '40 DC for parts did... I haven't put an ammeter wiring on it yet but wanted to see if the generator was even alive before I shelled out the $. Anyway, I don't see how to adjust the 3rd brush on this one and I'm pretty sure that's my big issue. It blows the internal fuse on the generator with the output completely disconnected (even from the regulator). I'll start poking around to see if I can move the third brush somehow for the adjustment. Due to the straight thru shaft for the magneto, it's not like the other ones I've seen.

Thanks!

Ken in AZ

 

[mEl]

(quoted from post at 19:34:52 10/11/11) Hi mEL,
The generator is the one between the mag drive and magneto on this setup. The DH didn't have electrics but the '40 DC for parts did... I haven't put an ammeter wiring on it yet but wanted to see if the generator was even alive before I shelled out the $. Anyway, I don't see how to adjust the 3rd brush on this one and I'm pretty sure that's my big issue. It blows the internal fuse on the generator with the output completely disconnected (even from the regulator). I'll start poking around to see if I can move the third brush somehow for the adjustment. Due to the straight thru shaft for the magneto, it's not like the other ones I've seen.

Thanks!

Ken in AZ

Please get an ammeter inline or at least get a wire back to the battery so you have a load on the genny so you can properly read and set your voltage, an open post will allow voltage to rise much higher than a loaded genny will, I doubt that that genny if stock will charge more than a few amps but I could be fooled. Try to figure where in the circuit the fuse is located, what does it protect, it either has to be in the output circuit or the field circuit.

 

[Ken in AZ]

Hi mEL,
I currently only have a 12 volt battery that's not connected. I haven't bought a 6 volt for it yet but as soon as the budget allows I'll get that squared away (battery, wiring, ammeter). The fuse appears to be on the field ground inside the generator and I'm guessing that with the output unhooked the voltage can skyrocket and cause the voltage and current going to the field coil to go way out of range and blow the fuse.

Unfortunately my day job is holding back my tractor generator repair until the weekend as well. I'll let you know how this works out.

Thanks again for your help!

Ken in AZ