wtm@uhura.neoucom.EDU (Bill Mayhew) (06/28/90)
I believe the fan itself does the temperature sensing. The power supply does, of course, have a Klixon thermal cut-out. Apparently the power supply can still get pretty darn hot under fault conditions because I have heard more than one horror story about melted 7300 cases. Not all 7300s and 3B1s have the same fan arrangement. Some early 7300s have two fans, while most 3B1s have only one fan in the cut-out behind the power supply. The common collective Usenet wisdom is that one fan is better than two beccause the air flow pattern is supposedly better with a single fan. A number of people have replaced the 12v DC operated fan with a line oeprated AC fan. A little load is taken off the power supply, but rewiring and splicing into AC leads inside the machine would be necessary -- do at your own risk. I stuck with the DC fan. I have a Radio Shark temperature controller ($19.95) probe stuck in the fan grille of my machie. At the moment, the exhaust air is about 90.3 F with 2 meg RAM, Voice Power, and Miniscribe 6085. I am considering updating my reboot sanity timer to monitor the overtemp output from the Radio Shark module to force the 3B1 to shut down if the fan fails suddenly. ==Bill== -- Bill Mayhew Northeastern Ohio Universities College of Medicine Rootstown, OH 44272-9995 USA phone: 216-325-2511 wtm@uhura.neoucom.edu ....!uunet!aablue!neoucom!wtm