Please Help Miller 875 Plasma Cutter

[Kitt1993]

Hello everyone


I've been in the metal fabrication for many years and finally was able to purchase a DOA Miller 875 Plasma Cutter off Ebay. I realize that its probably better to purchase a new one or one that works, but I like the challenge of diagnosing and repairing my own unit. That being said, according to the listing, its a 2016 Model and isn't turning on. Well It just arrived today and sure enough, theres no pulse. I was wondering if there is a diagnostic procedure on what boards to test in what order. I called Miller and they weren't very helpful and suggested that I throw away the unit, again I realize that its not worth repairing, but I want the experience and the opportunity to get to know this unit in and out.

Appreciate any support.


Bryan

 

[RacerX]

Have you looked for or do you have the manual for the unit?

They are inverter units, so what usually happens is the input voltage is frequency increased and then the signal cleaned up.

Input power usually has capacitors that fail and need replacement. Check for any burned components, failed fuses, burned circuit board traces, etc.

Next would be check some Google searches for common failure points on these units. Surely yours isn't the first one to fail like this.

Sent from my SM-N960U using Tapatalk

 

[Kitt1993]

Have you looked for or do you have the manual for the unit?

They are inverter units, so what usually happens is the input voltage is frequency increased and then the signal cleaned up.

Input power usually has capacitors that fail and need replacement. Check for any burned components, failed fuses, burned circuit board traces, etc.

Next would be check some Google searches for common failure points on these units. Surely yours isn't the first one to fail like this.

Sent from my SM-N960U using Tapatalk

Hi Racer,

I plan to take it apart this weekend and see what I can find out. I found the manual online and it speaks of a inline fuse, but I'm pretty sure they are referring to a fuse instead of a circuit breaker in a panel. I've searched google and Youtube with no luck. Any idea where I can find a internal schematic?

Bryan

 

[RWL]

Hi Racer,

I plan to take it apart this weekend and see what I can find out.
Bryan

Did you look inside? What are you seeing? If not sure what to look for, the things you can do are look for blown fuses, burned traces or burned components, capacitors whose tops are bulged upward a little, or have leaked at the bottom. Beyond that I think you'd have to unsolder and test individual components. If you do find the problem, it's helpful to report it so that there's a record so others doing repairs can add to the knowledge base.

 

[930dreamer]

Post some pics of the insides.

 

[RacerX]

Usually with Miller products, their manuals are great at having schematics and troubleshooting information for repairing their units. See if it comes with it or you can locate the pdf of the manual online.

Sent from my SM-N960U using Tapatalk