GYSMI 160p welder transistors shorted

[vbogoev]

Hello,

Here I have GYSMI 160p welder with no output. Otherwise the machine is starting, the fan is spinning, but the output is zero... I disassembled the welder and found the problem. 3 out of 6 transistors are shorted, and 3 pairs of 4 resistors are burned... There's also 1 burned "ultra fast diod" on another board that is connected to the transformer. My question is how can I identify these burned resistors, I have no idea what value they should be, also I am not able to find any image of the board over the internet... The other part numbers are clearly visible, so I won't have any problems replacing them. I assume one of the 3 transistors got shorted and then the disaster happened... All resistors have holes on the same place, so no way to read the value... Attaching some images of the board. All other elements are measured good.

Thanks

[R_J]

Re: GYSMI 160p welder transistors shorted

The resistors look like R100 which would be 0.1Ω They are emitter resistors for the IGBT If the transistor is shorted it may have damaged the gate drive circuit as well

[CapLeaker]

Re: GYSMI 160p welder transistors shorted

I am thinking someone had welded with this thing on full bore for too long and then it went down the hill fast. As RJ already mentioned above, I say too the resistors are R100. Just make sure you inspect the gate drive if the IGBT thoroughly. You can check the gate drive with the IGBT’s out.

[vbogoev]

Re: GYSMI 160p welder transistors shorted

Thank you guys for the responses. I'll try it with R100, Didn't think of the gate drive, but you're right. I'll check it as well. I'll update after I replace all the components..

[R_J]

Re: GYSMI 160p welder transistors shorted

If the drain shorts to the gate, whatever that drain voltage is gets sent to the drive circuit and in most cases the drive circuit can't handle it.