Gentlemen,
Both Guns and Tranz4MR are correct, if the ZW is real hot you have a problem, however some of the early 1st generation 275's run real warm compared to the later ones. I have both older and newer 275's and a couple 250's also, the 250's never get as warm as my 1st generation 275 does. It has however functioned perfectly for many many years.
Pine Creek/Dave