Drive motor on Mastercraft MIG welder stopped working.

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Steve the motor is 12 v dc. It will vary in voltage depending on where the speed control is set. You can jump a couple wires from a good battery and se it the motor will spin.
 
Thanks for chiming in. I got no voltage at the terminals on motor whether trigger is pulled or not. The tag on motor says 24V?
Steve the motor is 12 v dc. It will vary in voltage depending on where the speed control is set. You can jump a couple wires from a good battery and se it the motor will spin.
 
You ma be correct that it goes up t 24 v. Let me look in to it Monday when I get in to the shop. I will try and give you a couple more things to look at
 
Time to pull circuit board and grab a magnifying glass. Look for little circular cracks around all the solder joints.
88-98 chevy pickups had issues with wiper motors.many wouldnt work in the rain. All due to a broken solder joint. I must have repaired 50.
 
Pulled the cover off. Strictly clicking at circuit board.
I tried with the cover off the trigger, could see where the contact is made. Still only a click at circuit board.
What should voltage be on either side of trigger?
Thanks all.

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If you get a solenoid click when you hit switch,then i would assume its working.
 
The small transformer would be putting out voltage to trigger relay,and power the board. So my guess is the motor driver circuit.
 
So 12v directly to motor and it spins.
Frank that 24v dc relay is what's clicking. 2 wired going to it a black and a white. Cant unplug the wires from it. Sure as **** I'll break it or the board. Board "looks" good, I cant see any breaks anywhere. No sparks when I try in the dark.
The wire speed control potentiometer looks to be crowding something on the board?
Thanks
The small transformer would be putting out voltage to trigger relay,and power the board. So my guess is the motor driver circuit.

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I see the transformer in my reply #33, the 2nd pic. It's got a yellow covering. The 2 blue wires are smaller sized wire, so is that the low side?
 
The relay switches the high voltage side for the arc, there is 24 to the relay,but not to the motor. Board must be the issue.
 
The relay switches the high voltage side for the arc, there is 24 to the relay,but not to the motor. Board must be the issue.
Hi Steve, Are you isolated at home, good idea stocking up on booze, keeps the insides clean,
fixing this issue should take up a few days or weeks, on the electrical forum one of our members
mentioned you had special crimpers for wire repair etc. I need a fusible link for my 75 Duster.
As you know I work in grocery, working our a$$es off and scared to death because people don't
take this serious, trying to get parts lined up for when we get stuck at home,
Stay safe and healthy. Dave
 
Hi Dave, I'm self isolated, on standby this week for work. Then off the following week.(scheduled time off) So my spot in rotation worked out good.
A gentleman in Lindsay died from Corona. He lived in same appt building right beside my buddies moms apt!
My friend was at his moms apt dropping off bottles water yesterday.
Yeah you being in grocery is dangerous/stressful territory! Thanks for what you do!
I do have Iwiss wire crimpers, I tried crimping new open barrel terminals and they sucked. The dies werent machined to tight enough tolerances. Has interchangeable dies.Not sure how other dies crimp.
Too bad as they are sturdy feeling ratchet style. Only $36 delivered on Amazon.
Be safe and healthy!
Hi Steve, Are you isolated at home, good idea stocking up on booze, keeps the insides clean,
fixing this issue should take up a few days or weeks, on the electrical forum one of our members
mentioned you had special crimpers for wire repair etc. I need a fusible link for my 75 Duster.
As you know I work in grocery, working our a$$es off and scared to death because people don't
take this serious, trying to get parts lined up for when we get stuck at home,
Stay safe and healthy. Dave
 
Steve
Here is a wiring diagram for the machine. It doesn't do alot of good but is a bit of help
Main Circuit Chart - Mastercraft MIG Instruction Manual [Page 34]
If you are getting the click of the relay on the board then the gun trigger is good and the board is getting the 24v it needs to operate. Since you ran power to the motor and it spins then that only leaves what tooljunkie pointed to, the control board.
 
Thanks, I was able to get circuit board out. The female connectors to the relay were a bear! Everything on board looks good. No broken cracks/solders that I can see. The only suspect area is by the wire feed dial/potentiometer #B470k? But solders appear crack/break free?

Steve
Here is a wiring diagram for the machine. It doesn't do alot of good but is a bit of help
Main Circuit Chart - Mastercraft MIG Instruction Manual [Page 34]
If you are getting the click of the relay on the board then the gun trigger is good and the board is getting the 24v it needs to operate. Since you ran power to the motor and it spins then that only leaves what tooljunkie pointed to, the control board.

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So drive motor works with 12V applied direct from power source (car battery).
So that leads me to circuit board and relay. I am NOT electrically inclined AT ALL. Relay clicks when trigger is pulled. Relay is 4 pin(see pics) but not sure where to put test leads to check? There is no layout printed on side of relay?
So I figured I would move on to the wire speed controller (potentiometer).
#'s on it B470K.
I checked for resistance with motor speed at lowest setting with test leads(see pics)on outer and inner connections near zero
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ohms.
Then dialed switch to max with leads in same position. 469k ohms.
Switched leads to connections. Readings were opposite. From what I've watched/read this is good?
Any ideas how to test relay? The relay appears to be obsolete, but found a "similar" one on ebay. Dont want to order one if that's not the problem.
Thanks
Steve

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