DOES ANY ONE KNOW ABOUT THIS HOBART PLASMA CUTTER AIRFORCE 250A SS# LF070449P IT HAS ITS OWN AIR CYLENDER . I CANT KEEP IT CUTTING MORE THEN 3 SECONDS THEN I RESET THE HAND TRIGER THEN IT COMES BACK ON FORE ANOTHER 3 SEC THEN GOES OUT AGAIN. HELP HELP....... THANKS