Miller bobcat

Mike L · Jul 24, 2020

my bobcat 250 quit welding the other day but would still rev up when I tried to strike an arc. Generator not working as well. Don’t know much about these things but I tried to clean up the brushes and copper wheel things that they ride on. No go. Roughly a month out to get it looked at, much less repaired. Guy at welding shop mentioned a big plug in there loosing contact. I’ll check that tomorrow but if that’s not it I’m probably gonna buy a new machine. I can’t go a month without a welder/ generator. $4300 for a bobcat 225 and $4900 for a 250. Sales guys keep asking if I need the gfci. It’s mounted on my service truck. Do I need that or not? Also any other suggestions on what happened to my current machine?

Bls repair · Jul 24, 2020

When read the book for the 225 I had it mentioned fuses in the system . Never had a problem so I don’t know where they’re at.

Bls repair · Jul 24, 2020

I would call or email miller service they always helped when I had questions.

Mike L · Jul 24, 2020

I talked to 2 different miller dealers and one welder repair man. I asked about fuses or breakers but was told it didn’t have any. I would definitely rather fix it than spend the money, I just don’t have the time to send it out if it’s something I can’t figure out. I’ll send an email directly to miller and see what happens.

funwithfuel · Jul 24, 2020

On the face of your welder is the serial number. Look on Miller's website. They have manuals for parts and service free for download in pdf.

Bls repair · Jul 24, 2020

I wasn’t talking about dealer mechanics I was talking about corporate service reps.
Good luck.

funwithfuel · Jul 24, 2020

GFCI must be in place and operational if going onto mine property. All outlets must have covers, in good order, including cable lugs. Some guys specifically ground the welder to the chassis and throw an outrigger down to satisfy MSHA inspectors if they're doing welding repairs. Dirt works couldn't care less. As long as their junk is getting glued together, they don't care.

Vetech63 · Jul 24, 2020

I have 2 225 bobcat welders. Both great machines, 1 being 12 years newer than the other. My older one did something similar so I took it in to the repair center here. I don’t remember what they found but it was $700 to repair.

Mike L · Jul 24, 2020

I just found the owners manual and in the troubleshooting section it said to check 2 fuses and a plug and after that to take it to my authorized dealer. Both fuses were good and plug was clean and tight.

MarshallPowerGen · Jul 24, 2020

See if you're getting excitation voltage to the brushes, that will tell you which direction to follow.

willie59 · Jul 24, 2020

MarshallPowerGen said:
See if you're getting excitation voltage to the brushes, that will tell you which direction to follow.

I maintain and repair about 30 of these machines. 9 times out of 10, if the weld stops working as well as the AC power it's the brushes are worn out at the exciter ring, rather easy fix if that's what it is. You have to remove the black steel cover on the generator end of the machine, remove the two phillips head screws that hold the bush holder in place and remove the brush holder. If those brushes are only sticking out of the brush holder about a quarter inch or less, it's done. New brushes stick out of the brush holder about 3/4 of and inch.

Mike L · Jul 25, 2020

I would say that might be my issue. There is no way that the brushes have 3/4” . Closer to 1/4”. I found the part numbers for new brushes and an exciter ring because mine is a little blackish and will order them on Monday

crane operator · Jul 25, 2020

willie59 comes through! Hope its just brushes. That's sure better than having to buy one just because of a long repair time.

willie59 · Jul 25, 2020

Yep, if those brushes are down to a 1/4" or less they're done. Check the exciter rings, unless they are damaged I wager they're still good, the blackish would be from the brushes breathing their last breath. Clean the exciter rings with some Emory cloth and inspect them. If they're not damaged then you're prolly good there and just need to replace the brush holder. Of course you could still have a problem with the two bridge rectifiers or the capacitor, but replace that brush holder before we go there as we may not have to if that fixes your problem.

Mike L · Jul 26, 2020

Got my parts ordered yesterday. This would be a better ending than the other option. Thanks again willie. Once again I’ve learned something new from you and the rest of this great forum.

Welder Dave · Jul 26, 2020

Sand paper is better than emery cloth as it won't cause arcing but either could cause scratches and/or leave grit. They used to make dressing stones for armatures but they're hard to find anymore. Some suggest using purple Scotchbrite pads to clean up the slip rings if they aren't too bad.

Mike L · Jul 26, 2020

I ordered the new brushes and the exciter ring. Figured for $80 shipped to my house I couldn’t go wrong replacing both pieces.

keith-50 · Jul 30, 2020

Not sure if you have fixed your welder, I also have a miller 225 welder that would not weld and had no power at plugs, found winding solder joint at slip ring for brushes one wire became detached from solder joint, you can use ohm meter to ck stator windings, I resold red wire instead of buying a 800.00 stator

Miller bobcat

Mike L

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Bls repair

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Bls repair

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Mike L

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funwithfuel

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Bls repair

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Vetech63

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Mike L

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MarshallPowerGen

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willie59

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Mike L

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crane operator

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