Esab PCM-875 Plasma Cutter Troubleshooting

[TBWeldor]

Well I called ESAB today and just missed them (darn time zones). I decided to dig a little deeper, as I was baffled that I couldn't see ANYTHING that could give a hint. I took the top Control Board off and took it in my office under really good light, and I couldn't see anything of concern. Back out to the shop to the machine... poking, prodding, peering with a flashlight... wait, what's that? Smoky Residue? (technical term there, right?) it looks like a Power Module might be blown. Quick google and it's readily available at about $120, $55 if I go through Malaysia and Amazon. I'd like to still talk to ESAB to make sure that this isn't a repercussion of a bigger problem, but man... if this is it...

[jimcolt]

Sure looks like an IGBT (insulated gate bipolar transistor) failure to me. Often caused by an input line voltage spike. If you are lucky that may be the only issue. Make sure when you replace it that you clean the mounting area well and replace the heat sink grease properly and torque the mounting bolts. Keep us posted!

Jim Colt Hypertherm

[Brand X]

I do know in some Esab inverters, Esab recommended replacing other parts (Another board) when the IGBT failed.. That was on a 350 MPI inverter, and might not be true in this case.. It is wise to contact Esab, and it would not hurt to PM. ccawgc at this forum. He is up to date on Esab, along with many more machine brands too..

[TBWeldor]

[/ATTACH]

Sure looks like an IGBT (insulated gate bipolar transistor) failure to me. Often caused by an input line voltage spike. If you are lucky that may be the only issue. Make sure when you replace it that you clean the mounting area well and replace the heat sink grease properly and torque the mounting bolts. Keep us posted!

Jim Colt Hypertherm

I do know in some Esab inverters, Esab recommended replacing other parts (Another board) when the IGBT failed.. That was on a 350 MPI inverter, and might not be true in this case.. It is wise to contact Esab, and it would not hurt to PM. ccawgc at this forum. He is up to date on Esab, along with many more machine brands too..

Thanks guys. According to the ESAB manual/parts list, this is not the IGBT, I thought it was at first as well, but the IGBT is up and to the right, it's the white component in this picture. It would probably be smart to test it as well though...

[jimcolt]

Maybe an input rectifier?

Jim

[Brand X]

I saw the Sanrex, and thought it was a IGBT. Esab/LTec had some Sanrax made plasma's too. The 875 are SC ones..

[TBWeldor]

I saw the Sanrex, and thought it was a IGBT. Esab/LTec had some Sanrax made plasma's too. The 875 are SC ones..

Great, thank you for the spec sheet. I just ordered the part, it should ship today. Hopefully this will do it!

[TBWeldor]

Well... no joy. I swapped the part and it's doing the same exact thing. Definitely need to call ESAB now.

[ccawgc]

Send me a PM with what this plasma is doing. What tests have been performed.
On the line side of the diode assembly there should have been 3 MOVs. They have a bad habit of blowing up when they get old. usually nothing else get damaged. in order for the buss caps to get voltage the resister at the end of the yellow wires must be good.
The MOVs can be removed for testing but if left removed the input diode will get damaged.
Did you power up this unit and pull the trigger. observed the HF spark gap operating?
If so we need to disable the HF, and try to measure the OCV work clamp to electrode and then nozzle. The HF will kill your meter. Send me the PM answer questions, I will give you next steps and how to disable HF.