I have a TB250G, 1100 hrs. Thursday went to a job & welded about 15 ft. with mig & when I went to grind, welder revved up but no 110v power. Swapped grinder, eliminated ext. cord, checked breaker resets, all o/k. Shut off machine while thinking, started it up to see if it would weld & it had 110v power now. Finished grinding, grab the gun & now no juice to the feeder. Shut it down & started it up again now all is well. Friday no problem. Today on my second job I was stick welding & changed rods & now it won't weld. Checked all the connections, flipped switches, nothing worked so I shut it down, started it back up & it worked fine. Happened again a little while later & after shutting it down it worked fine again. Finished up the last couple rods & packed up. Now I'm worried about it crapping out somewhere in the middle of an important job. I don't know where to start to look, any ideas?