Question about Miller Spectrum 375 Cutmate Plasma Cutter 903891

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Cup light is on machine will not work

Is the cup the glass container how do you reset

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The cup light is referring to the outer most part on the torch tip, the purpose of the cup is to create a gap between the tip and the work piece. The light is indicating that the cup is worn and must be replaced.

Posted on Nov 13, 2008

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My plasma cutter miller 875 want arc the cup light flashes for 15 seconds I replaced the cup and o-ring and tip still nothing

Check the cable connection to the cutter head and at the box. Also check to make sure the control boards are blown clean of dust.

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Check connections on holder and at the main unit. blow out the unit with air to eliminate conductive dust as being a problem. Also make sure cup seating area is clean.

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look at your duty cycle 40 % duty cycle is 4 min 10 min sraight is minimum 100%, but good machines weld for 3 or 4 shifts till they get turned off

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A red fault light is illuminated all the time it wont work

The 3 reasons which will cause the infamous red light of death to come on and the machine not function, is because of over/under voltage protection,( make sure you have adequate voltage to the machine) thermal protection (because the duty cycle was exceeded), or mosfet failure. Assuming you have the correct voltage, and the machine is cold, try opening the case. Attached to the aluminum heat sink housing the mosfet transistors is a small button sized metal pill with 2 wired attached to it. This is a bi-metallic thermal fuse, when it gets hot, the contact points inside will open up, and cause the machine to shut down. Check for continuity, because sometimes these contact points inside dont re-align correctly, and your machine thinks its always too hot. If you plug in the machine, and it seems to work, but when you key your plasma torch, everything shuts down and the red light comes on......then theres a good chance the mosfets are gone. When they go, there paired off in series of 3, Chances are youll need to change all 3. Hope this helps........

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I would recommend replacing the electrode, and maybe the tip, other that that it sounds like you aren't getting a good enough ground for it to start.

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if the main power cable is cut that is your problem,unit uses high frequency.the two leads go to the gun trigger back to unit,no fuse or fuseable links in the gun.

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1 Answer

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check your torch and make sure nothing is loose. If that does not fix it you will need to disassemble the tip and make sure there is not any debris if there is clean it out and replace any worn parts.

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