Miller big blue 400P failure

[98G]

Yesterday I used it for fencing. Running a chop saw off the AC generator and using the welder for stick welding. Settings are coarse adjustment at minimum, fine adjustment at maximum, which should yield about 90 amps. 2/0 cable leads. 1/8" 6010.

Yesterday it worked fine. Today I got to the job site and fired it up. We used the AC to run the chop saw and got the first pipe cut and ready to weld. It won't strike an arc. I thought it was bad ground, or paint on the pipe. I moved the ground around and eventually attempted to strike an arc on the ground clamp itself. No go.

There is some power coming through - it sparks very minimally, comparable to static electricity. This is whether I strike the pipe, or the ground clamp. I attempted this on all coarse settings from low to high, and with the fine setting knob in various positions. Same result.

I checked all connections, positive and negative, from the machine to the ground clamp and from the machine to the stinger. Everything looks fine.

This is a 2007 machine, with a bunch of hours. It has been working fine for me without a hiccup up to now.

 

[Artisan]

Could it be possible the leads them selves are bad?

 

[goldneagle]

Could it be possible the leads them selves are bad?

I agree. Try new welding cables just to make sure it's not as easy as that. 2nd place would be the rheostats that control the voltage output. Maybe they are warn or corroded. I just thought about it... try a voltage meter at the pos and neg terminals.

 

[Jericho]

Check for out put on your plugs, Check your brushes and check for field output, Get the specs and if everthing is good and it still has no output them Ohm check the windings. eh If you have a cracked or bad brush or two it wont put out . If you have lost the field you can reflash in in a number of ways, Just look on You tube "reflashing generator field" Good luck

 

[Artisan]

I should have suggested wet or old rod too, but I did not because
98G is smarter than the average bear...

 

[Artisan]

I agree. Try new welding cables just to make sure it's not as easy as that. 2nd place would be the rheostats that control the voltage output. Maybe they are warn or corroded. I just thought about it... try a voltage meter at the pos and neg terminals.

Rheostat or Potentiometer ?

 

[98G]

I immediately suspected (and continue to suspect) the rheostat.

The leads are nearly new 2/0 cable. It seems unlikely they'd be the culprit, but I'll rule them out by trying others.

The rod was new and clean and dry, but of course I tried several different rods from several boxes.

I thought maybe someone on here had a similar experience and would be able to give me a definitive answer. I continue to hope...

Thanks for all the replies....

 

[gimpyrobb]

It has been tested over on weldingweb, you can have wet rods and they still weld ok. I doubt that would be the issue

 

[98G]

I've welded with rods directly from a puddle of water. They sputter and act funny, but they weld. This isn't that, and besides I ruled it out with various types of known good rods.

 

[royalflush55]

You might check the wiring from the alternator to the exciter rotor. The exciter rotor gets it signal from a hot post on the alternator.

 

[m16ty]

It's almost got to be something inside the welder. A problem outside the welder would be obvious. In other words, you're not going to have something like a break in a 2/0 cable without it being readily noticeable.

 

[porkysplace]

I've welded with rods directly from a puddle of water. They sputter and act funny, but they weld. This isn't that, and besides I ruled it out with various types of known good rods.

Soak the rods in water and crank the amps up and they will cut just about like a torch.

 

[98G]

Welder is fixed.

Fine adjustment control (potentiometer)failed. It has been replaced and all is well.

A strong endorsement to WeldRite in Tucson.

 

[silverstate55]

WHEW!! Good job!!

 

[tobyS]

Had some Lincoln bullets with a similar problem. It was brushes.

 

[goldneagle]

Welder is fixed.

Fine adjustment control (potentiometer)failed. It has been replaced and all is well.

A strong endorsement to WeldRite in Tucson.

Looks like my guess was correct. Do I win the contest?