Miller 1E Welder Generator update

[Tom Reed]

Well I spent some time working on the welder this weekend. Pulled the circuit board and tested the diodes. Diode D5 was found to be bad, conducted in both directions. It was replaced and the board was reinstalled, started the engine and flashed the generator and the engine loaded down a bit and it started making voltage at the power outlets. Yay, for about 30 seconds, then I heard a muffled pop and voltage dropped to 0. Tried a reflash and nothing. Checked the field windings at the slip rings and found high resistance. So bummer it looks like it has a bad armature. Does any one know if there is a common failure spot on these? And/or what would one expect to pay a rewinding shop to repair it?

[mobile_bob]

if you have high resistance at the slip rings, it makes me think that maybe the sliprings
are dark and not bright and shiney?

i would clean them up nice and bright with a piece of fine sand paper, wrapped over the end of a stick, so you can apply it to the spinning rings while the engine is running.

it really doesn't take much to loose connection here, and doesn't take much to get it reestablished either.

then if no joy, recheck for continuity of the field coils, if there is continuity the problem is back at the board.

if there is no continuity, check each brush to ground by slip ring to shaft or rotor iron
if there is a short then you are going to have to pull the rotor.

if there is no continuity and no short, you might get lucky by resoldering the leads from the slip rings to the leads to each pole of the field, also...

carefully check the crossover connection from one pole to the next, look for a broken wire or a short to the shaft or iron core.

in my experience the rotor is one well built unit and not likely to be burnt out, however anything is possible.

once you get to the point of removing the rotor, get it under a bright light and look it over very well, if there is a fault you ought to be able to find it and figure an effective repair.

if you get it out and it looks like it is cooked, you will have no choice but have it rewound, or rewind it yourself.  you might check with miller they might offer and exchange rotor?  stranger things have happened.

if you have to have it rewound, find a shop that looks like they have been around a while and shop around till you find an agreeable price. the upside of having it rewound is they will vacuum dip it and then rebalance the rotor when they are done.

it should be less expensive to rewind the rotor than the stator.

bob g

[Thob]

Tom,

I'm concerned that there's something we're overlooking here.  When the engine loaded down, was there any load on the generator?  If not, then that would indicate that something was going wrong in the generator.  If the loud pop was the field coil burning up, then you can get it rewound, replace the diode (again), and still have a problem that burns up the new coil.

Are there still welding leads on this unit?  I can remember my dad starting his welder with the leads shorted - lots of grunting on the engine and him running around the other end of the welder to pull the leads loose (when finished, he had a habit of turning the welder off then winding the leads up, finished by clamping both leads to the frame to keep them wound up).

[Tom Reed]

Slip rings are shiny, already did the sand paper trick. Will check for short to ground. The engine didn't load down much, just a bit. The field coil does not look or smell burnt, in fact the cloth covering is not even discolored. Unfortunately other projects are moving to the forefront. Things like fire wood to keep us warm this winter and the top to my Scout needs to be repaired and repainted before the rains start. The next 2 weekends are booked up too, so this project will probably need to go on hold until next year.