Author Topic: Chinese plasma cutter repair  (Read 4132 times)

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Offline Puffie40

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  • Country: ca
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Chinese plasma cutter repair
« on: September 14, 2015, 08:54:33 pm »
I have a Simadre CUT50DX that I bought as a non functional device on eBay.  The only symptom right now is the O.C. light triggers when the torch trigger is pulled.

The air solenoid activates on the trigger as well; the torch I am using is a P80.

After dismantling, a visual inspection of the boards reveal no burned or damaged components.  I found a shorted diode IC on the middle board, and replaced all of them with like components from DigiKey.

The HF diodes on the bottom board tested okay.  I have not yet tested the MOSFETs by function, but they did passed a diode test on my multimeter.

I am wondering if you have any other suggestions on where to look.  So far all the major components have passed testing
 

Online SteveH

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Re: Chinese plasma cutter repair
« Reply #1 on: September 16, 2015, 09:06:32 am »
O.C. light coming on with operation of torch trigger usually means at least one damaged IGBT/MOSFET. Using a diode test won't find them. I find them by using my DMM set to measure resistance. I repair these wretched things as part of my day job. Good luck!
 

Offline Puffie40

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  • Country: ca
  • Irregular Logic
Re: Chinese plasma cutter repair
« Reply #2 on: September 20, 2015, 06:52:02 am »
I desoldered the MOSFETs from the board and tested and retested them by this method: https://www.utm.edu/staff/leeb/mostest.htm.  They all pass the function test.  I also tested the gate resistors, and they are all good too.

I searched for Over-Current light on google (What O.C. stands for in the first place), And I found this: http://www.mig-welding.co.uk/forum/threads/over-current-fault-on-cheap-chinese.5218/ The guy there mentioned he unplugged a thermistor that was taped on one of the output transformers (The middle board) and the machine started working again.

Since mine has a sensor there as well, I'd thought Id remove it and check it out. - turns out mine is a normally closed bimetallic switch that opens at 100 degrees, and it looks like it's stuck open. :palm:

Well, time to find a replacement and test!
« Last Edit: September 20, 2015, 07:23:09 am by Puffie40 »
 


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