Miller Bobcat 225NT weak arc

[jezow2010]

Not sure if there are any welder guys on here but figured it’s worth a try…

Bought a 225NT that the history wasn’t really known on. Runs great, seems to generate AC power great but when I go to weld it just can hardly sustain an arc. Makes 120 and 240v.

The field coils on the rotor have about 25VDC when it’s running with the fine adjustment set to 10

The open line voltage between the welding terminals is about 55 volts dc when it says I should be getting 73.

I did check the diodes, fuses, resistors and everything checks out. The fine adjustment is a little corroded but it’s bad in the middle, not at the ends. Reads 10 ohms on low adjustment and 0 at high. I don’t think this is my issue?

Again, not sure, if anyone has experience or ideas let me know.


Thanks!

 

[Welder Dave]

I think there are slip rings that can be cleaned up. Someone on Welding Web could probably help in the Miller forum. Might even be able to do a search and find how to fix it.

 

[jezow2010]

I think I got it... the slip rings and brushes were dirty yes, for some reason one brush had like 1 ohm across it when it is supposed to be 0 so I replaced those.

It was a bunch of little things but ultimately what did it was the 12V charging circuit. Someone tipped me that the field in the rotor uses battery voltage to excite so unless you have a good 12V and it is charging it won't have enough power there to excite properly. She welds ok now, if only I was a better welder!

 

[jezow2010]

Pic

 

[oarwhat]

What rod are you using? I'm not a welder by trade but, I've never seen that much splatter from a rod.

 

[HarleyHappy]

It’s that friggin orange flux 6010. I bought 10 pounds of it 5 years ago and have 9 3/4 pounds left. Bunch of junk, that crap is. Has excellent penetration on rust and paint but it’s 50% spatter and 25 percent weld, rest is flux.
Think I’m gonna end up dumping it in a hole.

 

[jezow2010]

lol, what kind of 6010 do you like? not orange flux?

 

[SLK001]

6010 has its uses - like for penetration on rusty metals, it can't be beat. The rod burns faster than the coating, so you have a jet of super hot plasma burning into the metal. Almost nothing can resist the hot plasma, so you always get deep penetration. It does splatter a lot.

If you're a beginner, get some 6013 and 7018 rods. They are almost fool-proof. Keep the 6010 - you never know when you'll need to weld some rusty metal.

 

[HarleyHappy]

I prefer the Lincoln 6011.

 

[Welder Dave]

Glad you got your welder figured out. Looks like Lincoln 5P 6010. 5P+ with kind of a white flux is nicer to run and 6011 is a little smoother and less spatter but not quite as much penetration. The way to burn these types of rods is to use a slight whipping motion. You go ahead a bit and burn a groove into the steel then back up a bit to fill the crater. Go ahead say a 1/4" and then come back an 1/8" of an inch. You may have had a long arc that caused more spatter. The rods could have been too dry as well. Yes, too dry. 6010 and to a lesser extent 6011 need about 5%-7% moisture in the flux to burn properly. You can actually dip them in water, wipe them off and start welding. Don't do this with any other rods. I'd bet if you dipped the rods you have in water and ran some beads you'd see a difference in how they burn and the spatter levels. To set your heat close you can almost jam the rod into the steel and set the amps to where the arc doesn't snuff out. Typically 6010/6011 burns about the same amps as a size smaller rod like 7018. 7014 is an easy rod to use and much better than 6013. 6013 is only good for sheet metal and not a rod welders ever use. For the strongest welds you can run a 6010/6011 first pass and then run a 7018 over it. 7018 is by far the strongest rod and once you get it figured out is really nice to burn. A little less slag than 7014.

 

[oarwhat]

We use 6011 on rusty metal and 7018 on clean or prepped metal. 6011 welds ok with some spatter and has good penetration. 7018 is easy to weld with, has little spatter, good penetration and is very strong.