Hi everyone, apologies to bring problems as my first post but i'm in need of some more experienced folks than myself to help diagnose this.

So I have a Parweld XTM 201i Mig Welder, its been a great little machine and never had any problems with it, until a few weeks ago it went pop upon turning on the machine (no trigger pulled, just plugged in and turned on made it go)

Now, being that I have no warranty and am also somewhat electrically experienced, I had the cover off to find a group of 3 resisters completely obliterated. I have no schematic for this machine and parweld wont even reply to my emails when i ask politely as a loyal customer for information that would cost them nothing to give.

I suspect one of the following two scenarios (or perhaps some strange combination of the two) has occurred.

Scenario 1: Dirt caused a short. Why do i suspect this? because there was some evidence to suggest the sleeving on the ground/earth lead that runs across the board (which was quite filthy i must admit) had conducted some of the blast (blackened and heat evidence - faintly visible in picture)

2: Something has gone wrong with a one of the IGBT's (CHINESE ONES.....IN A MACHINE THATS COSTS ~£1000!! - Stands back in utter disappointment!) or perhaps one of the gate driver circuits. I have, however, checked as best I can and found all but 2 of the transistors read good, 2 are showing open on all connections but I wont know if thats "true" until i test them off the board.

I guess what I would really like to know is, what values would these 3 resistors likely be, and does anybody have the foggiest idea how I can go about saving this from the bin!

Thanks to any help in advance!

 

I don't know if this is still relevant to you or not mate, but a couple of photo's of the other side of the board would help for a start,

Are both IGBT's the same?

Im guessing these are the two IGBTs see att. If so its not the gates. The base of the IGBT's would be the left ones with tiny traces leading to control circuitry that would appear to be on the other side of the board

If you just googled the PCB you might find a photo of the board that might help you faster?

Regards,

 

Thanks for the help, this machine is now back up and running after replacing IGBT's and a couple of smd resistors, time will tell if the repair will last but its done a fair amount of work so far and hasn't missed a beat.


My suspicion is that the failure was caused by a short around the area of those resistors (grinding dust or similar) which caused some of the IGBT's to be damaged.

Cheers.

 

Certainly a short circuit caused by conductive particles can be very destructive. Some electrical circuits are protected by a spray on clear insulating coating. That may be a good choice in your application in the welder.
Really, you are fortunate that apparently no other parts were damaged.
Others may have specific products that they can recommend for the insulation spray-on.