Help me with my plasma cutter

Hi,
I have a SnapOn YA2001 plasma cutter which I believe is a Century 2040. I bought it broken but I got it working for one day, then it stopped working
again. When I first got it had a hard time establishing the arc. After it worked for one day it now has a hard time starting the arc again.
Can you help me with a couple of questions?
There are two leads going into the torch. One with a air hose and one with a braided wire in it labeled pilot:
http://home.hawaii.rr.com/shigeoka/plasma1.jpg
When I blow air through the air hose lead it comes through the torch fine. When I blow air through the HF lead no air comes out through the torch is this right?
Inside the cabinet the compressed air goes to a solenoid and then Y's off to the torch lead and to the HF lead. Without any hoses attached, full airflow comes out of the torch lead but only a minimal amount through the HF lead. This confuses me as well because I see nothing that would cutoff the air pressure to the HF lead:
http://home.hawaii.rr.com/shigeoka/plasma2.jpg
http://home.hawaii.rr.com/shigeoka/plasma3.jpg
Is this what should be happening?
The HF circuit sparks only for about 5 seconds when I press the torch switch. Is this right? Should it be on continously?
I would appreciate any help you can give me. Thanks.
Aloha, Russell
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I can try. I don't have a lot of experience with plasma cutters but since no one else has replied I might be able to point you in the right direction.
First off, just as a guess that sounds like what would have at one time been a dual gas plasma cutter that used one gas for cutting and one for cooling. It looks like they've adapted it to use one gas by connecting the two together but again that's just a guess.
Most plasma cutters that I've seen have a safety circuit that checks for certain things before it will work. It checks to make sure you have enough air pressure and it checks to make sure the torch consumables are installed correctly. There is usually a switch in the head of the torch that will not allow it to work if anything is missing or the shield is not screwed on all the way. Some units have lights to tell you what type of safety problem you have.
But it sounds like this is not a problem on yours if you're getting the high frequency. My unit is a newer style and supposedly doesn't use HF to start the arc but whatever it does use is only on for 3 seconds if proper cutting is not established. If you just point the torch at nothing and push the button it will fire for 3 seconds and then cut off. It will also do this if you don't have a good ground connection so that's something you might want to check.
As for the connections on your torch, I'm not sure why there are two lines because it's something I haven't needed to look into so far. I did a bit of checking on the Thermal Dynamics site because they have a good selection of manuals with schematics available and the nearest I could find to your setup is this one:
http://www.thermadyne.com/tdc/literature/pdfs/sales/0_2373.pdf
It is a dual gas system and shows a torch similar to yours so it may be worth your while to look it over to see if it helps. It has a troubleshooting chart and a flow chart of what happens when you press the button too.
Aside from that I have a couple of suggestions that might help. I'm guessing that the line you can't blow air through is the cooling line and it probably has quite a bit less flow than the main cutting pressure. Since the cutting pressure is usually something like 60+ psi you might have to put quite a bit of pressure on the line to get anything noticable through it. Also, if your torch is not together correctly you may have an O-ring or something blocking the holes that feed the cooling air to the torch head.
It's also possible that your hose is crimped or pinched somewhere cutting off the flow.
I hope it helps! Please let us know what you find...
Best Regards, Keith Marshall snipped-for-privacy@progressivelogic.com
"Even if you are on the right track, you'll get run over if you just sit there." - Will Rogers (1879-1935).

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Usually the HF comes on, initiates a pilot arc inside the torch and then the arc transfers to the work material to establish the main (cutting) arc, the HF shuts off as soon as the pilot arc is made, some will also shut off after a short period if the arc is not established. That is normal that it would expect to see a main arc within 5 seconds. Al

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