Millermatic 251 - no wire feed

[DanB98TJ]

I have a Millermatic 251 that I purchased new around 2002. It has been a great machine and has never given me a problem...until yesterday. I was welding in a tight area and the wire feed stopped. Figuring the wire fused to the tip I pulled the nozzle off and that wasn't the issue. Opened the cabinet and made sure the spool wasn't stuck and that wasn't it. Pulled the trigger to see if it had started to work and it hadn't, but I got a nice puff of smoke out of the front of the cabinet.

What is the best way to troubleshoot to see if this is a problem with the drive motor (I hope) or the board (I hope NOT), or maybe something else. The gas seems to be flowing briefly when I squeeze the trigger, so it doesn't seem to be an issue with the gun. I did check all the connections to make sure I didn't pull something loose, everything looked good there.

I'd like to figure this out myself if I can, not just for financial reasons, but I no longer have a truck or trailer to get this beast to a shop....

I would greatly appreciate any help! I have a few projects that are now indefinitely on hold until I can get it fixed.

[H80N]

Have you tried trading guns or jumpered the gun trigger leads at the front panel...??

[H80N]

Plug in your serial number here to download the manual

https://www.millerwelds.com/support/manuals-and-parts

[aametalmaster]

Sounds like a wire came off the trigger...Bob

[H80N]

Also...............

Have you cycled the breaker and measured to make sure that you have both legs of the 240vac coming into the welder....??

In addition... the front panel power switches have been known to fail... check to make sure that power is making it past the switch with a meter..

error messages...??.... or dark panel...???

[DanB98TJ]

Thanks for the ideas so far!

I plugged the welder in to a separate outlet (different breaker/circuit), no luck. Jumped the leads, no luck. The panel shows the voltage and wire speed settings properly, no error displayed. I can hear the solenoid for the gas cycle, everything seems to work fine except the wire feed. Of particular concern is the puff of smoke - smelled like burned electrical wiring/component - when this all started. I don't see any signs of burned wires or anything obviously melted/smoked/burned on the board. CB1 wasn't popped.

I am far from an electrical genius, so I'm not sure what the best way is to check the drive motor to see if that is the problem. I'm assuming - which I hate to do - that I can just pull the leads from the motor and see if I have voltage going to it. I read on another post that the motor can be tested using 12v, but would like to confirm before I hook it up and take a chance of damaging something that wasn't already screwed up....

[H80N]

Ya that smoke is concerning.....

Hopefully "Cruizer" will check in on this.... he is our resident service wizard.....

[DanB98TJ]

Well, I had a chance to open the welder back up and checked for voltage to the motor...nothing. Started looking around and found the board smoked near a heat sink on the upper right corner.

My questions now are:

1. What caused this?
2. How much will a new board cost (part number 205-716)?
3. Is there anything else I should check before spending any money? I would hate to pay for a new board, only to find out there are more issues....

As of right now my welding days are done - can't afford a new welder, may not be able to afford to have this one fixed....

[Miller Welders]

Well, I had a chance to open the welder back up and checked for voltage to the motor...nothing. Started looking around and found the board smoked near a heat sink on the upper right corner.

My questions now are:

1. What caused this?
2. How much will a new board cost (part number 205-716)?
3. Is there anything else I should check before spending any money? I would hate to pay for a new board, only to find out there are more issues....

As of right now my welding days are done - can't afford a new welder, may not be able to afford to have this one fixed....

We recommend giving us a call to talk it through further with a service tech. You can reach them at 920-734-9821. Let the operator know that you've got a Millermatic 251 and they will connect you.

Let us know if you have any issues getting through!

[cruizer]

Capacitor took an over load. Likely from the motor drive being wayyy tight, or the gun trigger shorted to the guns internal conduit while welding. On a 251, the display reads "Too Hot" when this occurs.


Just the motor circuit. I'd probably send it to PLC for over haul.

[DanB98TJ]

We recommend giving us a call to talk it through further with a service tech. You can reach them at 920-734-9821. Let the operator know that you've got a Millermatic 251 and they will connect you.

Let us know if you have any issues getting through!

Thanks! I will give them a call later this week.

[DanB98TJ]

Capacitor took an over load. Likely from the motor drive being wayyy tight, or the gun trigger shorted to the guns internal conduit while welding. On a 251, the display reads "Too Hot" when this occurs.


Just the motor circuit. I'd probably send it to PLC for over haul.

You're talking about the tension on the drive roll? I don't think I had it too tight, but I'm certainly no expert, and haven't messed with the tension in quite a while. I didn't see anything unusual on the display. When the wire feed stopped I looked and it still showed the voltage and wire speed. I was welding in a tight area so I thought maybe the wire fused to the tip (I've had that happen a few times) but it wasn't.

I appreciate all the help! I really would like to get it running again since I have a few projects I was hoping to start on, and this is kind of my stress relief after dealing with a lot of fecal matter at work....

[DanB98TJ]

Called this morning and spoke to John. It looks like the burned component is the transistor on the heat sink, which is for the drive motor circuit as suspected. John didn't think there was anything else that needed I needed to be concerned about since the motor was operating properly when hooked up to 12v.

cruizer - How would I check for the short in the gun? I would certainly like to rule that out as a possibility, and if I can figure out how to check the amp draw of the drive motor I'll check that as well.

Thanks again!

[cruizer]

Check the resistance from the guns trigger wires to the brass end on the gun or tip. Just take the #'s off HS!, order another from digikey. Get yourself a good soldering gun, some electronics solder and some solder wick and off you go.

[DanB98TJ]

Thanks - the welder has taken a back seat for now, but I'll try to check it out when things settle down. I appreciate all the help!