Any one know anything about welders?

[Stankfut]

My boss found out I do some work on electronics stuff, so I got voluntold to check out this welder we have. The drive motor is not working. We replaced the motor and the 1K speed control pot. Still not working. I checked the relay, there is continuity in the coil and the switches make contact, but there is a loud buzz when it engages when connected in circuit. Any ideas? BTW, its an ESAB Migmaster. Thanks!

[SILVERGUN]

Welp,,,it's what we do here...

When the relay closes, do you get voltage to the drive motor?....probably not, or it would turn,,,unless it's bad,,,not probable (but it happens)

I'll need the full model name and serial number...i.e.  Migamaster 250   s/n#

Does it look just like this?

[SILVERGUN]

The buzzing you hear is probably a separate issue...
On the pic above, #19,20 is the main contactor, and it is very common for those to buzz, as the coil starts to wear/weaken....we replace them all the time as preventive maintenance...
It is the main internal on/off switch for the weld power to activate by pulling the trigger....the more trigger on/off/on/off/on/off the sooner they wear out, the louder they buzz

The drive motor gets its control voltage from a speed control pc board(#14)....boards fail all the time

[SILVERGUN]

More here....

[Stankfut]

Its a lot like that, yes. ESAB Migmaster 250. Serial #MBBJ214064


No voltage to drive motor. The upper relay is arcing, figure it needs replacement for sure.


I'm thinking its a board issue, but that is beyond my experience to check. I figure they can't be repaired, right?

[Stankfut]

By the way, the drive motor he bought has two sets of leads (one near the gearbox and one at the end of the motor), the one that was in the machine only has terminals at the gearbox.....they look similar but are they interchangeable?


By the way....thanks so much for your help

[SILVERGUN]

By the way, the drive motor he bought has two sets of leads (one near the gearbox and one at the end of the motor), the one that was in the machine only has terminals at the gearbox.....they look similar but are they interchangeable?

They could possibly be interchangeable as long as it is designed to run off of the same voltages....and the mechanical connection is the same.

The extra set of wires is for a tach. sense connection in a different unit that would send the RPM of the motor back to the board.
The motor you have is not the right one for that machine, but it will run without the tach. wires connected, once you get voltage to it.

The board troubleshooting is easy (see instructions above)...you're looking for 30 vdc going in to the speed PC board,,and then a variable voltage coming out based on where the speed pot is set, when the trigger is pulled.

[Stankfut]

Cool, I'll look at it tomorrow.....slightly covered up right now

[Stankfut]

The boss sent the unit out.....good! I know the pros can do a better job for less money than I can

[SILVERGUN]

The boss sent the unit out.....good! I know the pros can do a better job for less money than I can

Cool, get it off YOUR plate...
I've got 5 bucks on the motor control board, and I checked and we have an open bag, used board here, if you need it. (I can discount it)
Let me know.

So take the time that you would've spent on that welder and work on your amp 

[Stankfut]

I would love to, but I'm in the moving process right now so my tools are packed up .