I have an old Migmate 100, but it hasn't had a lot of use. Got it out yesterday, set it up, and it started working fine on a piece of scrap for less than a minute. Got the job set up, and then it wouldn't work. I have power to switch which is lit. Thought it might be switch in the torch and stripped that. One red wire to trigger and a white wire which was not connected to anything and no obvious place that it had broken off. Any advice or tests I can make with multimeter if I take the cover off?