Help identifying resistor value

Thread Starter


Joined Dec 9, 2022
Hello, I'm a noob at this so please forgive me. Been tinkering around trying to repair a welder(Vulcan Omni pro 220) I had laying around. It died with a pop. Upon taking it apart I found a MOSFET that was shorted on Gate Source and drain(Toshiba 2SK3878). From the source pin is the resistor in the photo. It is open with no resistance. I assume with some of the ceramic off it appears to have went bad. If I turn on the welder the display and fans no longer turn on. When I opened it and LED labeled led 1 is on but that's it. I see LEDs 1,2,3,4,5 and 6 which are at different areas of the PCB. I assume this is to help troubleshoot and find where power is not getting to.

My question I need help with.
1. What value is r54 that is in the photo? It doesn't appear to follow normal standards.
2. It appears r59,r120 and dz10 got hot as well. (Coating that is on the board is dark and markings on these components are almost unreadable) does it make sense that r54 went bad and then MOSFET went bad which then started passing current through it's gate and heating up r59,r120 and dz10?

I could not find a schematic but put together this drawing while trying to trace the problem areas with a multimeter.

Thank you for any ideas.




Joined Jun 4, 2014
It is more likely that the MOSFET went short and damaged the other components.
Agree on R54.
The other possibly damaged components should be at least tested. If there is any doubt replace them too.