I have a couple of 24V DC power supplies that I picked up seconds hand a few years back. Last night while testing, one of these supplies was not working. On investigation, I found the problem, Gecko jamming the fan. On removal, everything seems to be back to normal. Note - these PS are model jws300-24, and have a fan that always runs. Before finding the gecko, I found that the PS would run for a few minutes before shutting down. Even on no load it became warm. Probably a good indication of thermal protection.