# Is this the correct forum to ask about plasma cutters?



## WobblyHand (Sep 16, 2020)

Maybe 15 years ago I bought a plasma cutter from HF.  It worked ok, but wasn't that great.  It cut the stuff I needed to cut at the time, so it was fine.  

Recently dragged it off the shelf where it was collecting dust and tried to use it.  Nope.  No pilot arc.  The SKU for anyone following along is 91814. The torch appears to be a Trafimet clone of the S45.  I get sparks if I drag it along the table, but no plasma.  I've tried replacing the consumables, including the nozzle, the electrode and the swirl ring.  No difference.  Adjusted the pressure up and down 15 psi from the recommended 65 psi. Removed the external moisture filter and just plugged the hose from my compressor directly to the regulator.  No noticeable change.  All appropriate idiot lights are lit.  Overload light is not lit.  The torch passes air for maybe 3-4 seconds and the tip is electrically hot for a few seconds.

I had the torch apart.  Everything seems to be ok.  About the only thing I can find is the spring loaded piston is a little stiff.  Sometimes it sticks. But air does come out, because I can see dust being blown.  On the other hand, I'm not positive it is coming out of the actual nozzle tip.  Maybe the air is coming out these 4 tiny holes.  It's not like I'm going to stick my finger in front of the nozzle!


Here is a figure from Trafimet how the plasma starts.


Could be electronic.  Unfortunately, the HF supplied schematic is useless.  None of the items (in the schematic) cross reference to the parts list.  

This is a shot in the dark.  Anyone have a clue as what to look for?  It does use a big IGBT device.  Can't find any evidence of a spark gap, like some older units have.


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## Wright40x (Sep 24, 2020)

Take the cover off and shine the points up with some sand paper


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## WobblyHand (Sep 24, 2020)

No points on this plasma cutter that I could find.  Not shown on schematic either.  Wish it was that easy.


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## Wright40x (Sep 24, 2020)

Then I’m guessing the tip has to have constant contact? My old plasma had points that needed cleaned from time to time but my new has a circuit board in place of points.


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## WobblyHand (Sep 24, 2020)

The torch is a pilot arc.  The documentation (from Harbor Freight) indicates it has pilot arc.  The arc should stay on for at least a little while, even if not touching ground.  It did, when I last used it many years ago.  Something has failed in the electronics.  Wish I had a clue what it might be.  A real schematic would be useful, the one in the manual isn't helpful at all.

Seem to remember that there is a series resistor on the pilot arc that can go bad.  It's shown on the schematic.  However, it's not identified on the parts diagram, nor obvious where it might be.  Suppose the unit could be disassembled some more.  You'd think a power resistor would be easy to find.


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## Wright40x (Sep 24, 2020)

I’m not much of an electronics guy I have always called a buddy and had him walk me through what I needed to do. If it were me and I knew the consumables were good I’d go hunting for the points/circuit board or what ever it had to take its place. I’m guessing with it’s age parts are probably non existent but I figure you could find a replacement resistor. Grab a case a of beer and spend an afternoon hunting.


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## 682bear (Sep 25, 2020)

Georges Plasma Cutter Shop in Delaware still services the HF cutters, if you decide you want a professional diagnosis.

-Bear


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## WobblyHand (Sep 25, 2020)

682bear said:


> Georges Plasma Cutter Shop in Delaware still services the HF cutters, if you decide you want a professional diagnosis.
> 
> -Bear


Thanks Bear.  I remember stumbling across his website.  May have to just send it in to him.  Now trying to decide if it is worth the cost.

Just wish there was a little more public info on the innards of the cutter.  Probably something dumb, like a burned out resistor buried in the unit.


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## mxr662 (Dec 5, 2020)

is this what you are looking for?


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## WobblyHand (Dec 5, 2020)

@mxr662 Wow!  It's a discussion about what it might be!  With some pictures!  Thanks so much for the link!  I'll have to disassemble this ugly unit further.    I was hesitant to go much further in the disassembly without any clues.  This gives me some hope to do a teardown.  You put a smile on my face.


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