Airco 300 Heliwelder IV Blown circuit board component

[joemazing]

Pictures

My welder started to weld as if my current dial was set to 0 at all times.
Upon examining the circuit board i found 1 transformer that blew up. I circled it in the picture. Unfortunately the label side of the transformer is the side that blew off. I do not know what exactly the thing is. There is another similar looking transformer with part number PN3645. My initial hunch is to just replace the blown one with the same type located near it on the board. However the back side of the 2 parts are slightly different. The one still on the board has a completely round back with color bands (yellow, red, orange) from top to bottom. the one i removed is only partially round on the very bottom then it's cut away to a flat surface. So if they are the same part they came from different manufacturers. Which is possible but not probable.

I'm hoping someone has a schematic of this circuit board and can tell me exactly what my bad part is.

[ccawgc]

The heliwelder IV is controlled by a mag amp. and the pcb is what controls the mag amp. The pcb is basically a light dimmer. First thing to check is the Mag amp and make sure it is not damaged or shorted to case. I was able to get a blown up pcb repaired by one of the pcb repair companies. installed it back in the welder and the pcb blew up again with in a few minutes. find a insulation tester or megger and check the mag amp from each wire to case ground. it is best to disconnect it from the wiring harness. I have a manual but there is no information on how the pcb is made, only the connections in the diagram.
according to the parts page there is a 40 amp triac on the pcb. so the transformer that blew could either be a power supply or the gating isolation transformer(pulse transformer). pcb did not die on its own. some thing killed it. and you need to find that first. If you want the manual ask for it by private message with your email.
I will get a email that you sent me a message and know to come back to the board.

[52 Ford]

pcb did not die on its own. some thing killed it. and you need to find that first.

Yes! This is something that I see overlooked fairly often when people let the smoke off of a component. They see that and assuming replacing it will fix the issue. Sometimes that's the case (old caps for example), but with something like a FET or a transformer, they're usually pretty foolproof on their own. Given, it could be something as simple as a lack of cooling. I suspect in this situation it's something else that's up-stream of the transformer that caused failure.

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