I had an mj 1200 go about a month ago. The gfci kept tripping. I isolated the pump; removed it a put it in a bucket of water to check it. Oops plugged it into a non gfci outlet. It started and stopped in about 2 seconds. Reached in to get it,ouch . After a nasty buzz,it was finally clear to me that the powerhead was bad. I looked it over and found a small crack on the inside top plate which was obviously compromising the seal.