Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!utgpu!water!watmath!clyde!rutgers!uwvax!uwmacc!uwmcsd1!marque!nic From: nic@marque.UUCP Newsgroups: comp.sys.att Subject: Re: Weird 3b1 fan behavior Message-ID: <1945@marque.mu.edu> Date: Mon, 30-Nov-87 09:00:51 EST Article-I.D.: marque.1945 Posted: Mon Nov 30 09:00:51 1987 Date-Received: Wed, 2-Dec-87 04:59:34 EST References: <21740@ucbvax.BERKELEY.EDU> <313@bilanc.UUCP> <624@pttesac.UUCP> <626@pttesac.UUCP> Reply-To: nic@marque.UUCP (Nic Bernstein) Distribution: na Organization: Marquette University - Milwaukee, Wisconsin Lines: 61 Keywords: UNIXPC 3B1 fan power In article <626@pttesac.UUCP> vanam@pttesac.UUCP (Marnix van Ammers) writes: >In article <624@pttesac.UUCP> robert@pttesac.UUCP (Robert Rodriguez) writes: >>Anyway, up until the repairman did this, my fan had *never* changed speeds. >>But, you guessed it, now it does it about once an hour. Seems to go into >>overdrive and the air being fanned out is pretty warm. >> >>This raises some interesting questions, maybe some AT&T guys can answer. >> >Yes, it does raise very interesting questions. You and I got >our 3B1's at the same time. I've added a EIA/COMBO board with >1.5 Meg on it and a DOS73 board. My far has only been at one >speed since day one. If we have dual speed fans, I would expect >mine to have changed speeds after adding those two boards. > >Maybe I somehow have a newer issue fan which runs only at the >single, higher speed? > >I would like to know for sure that my 3B1 will shutdown safely >if my fan stops. Someone in the know please enlighten us. > >Marnix >---- >-- >Marnix (ain't unix!) A. van\ Ammers Work: (415) 545-8334 >Home: (707) 644-9781 CEO: MAVANAMMERS:UNIX >WORK UUCP: {ihnp4|ptsfa}!pttesac!vanam CIS: 70027,70 >HOME UUCP: pttesac!Marnix!vanam Well this has gotten out of hand in my mind so, just to add to the confusion, and maybe a possible solution... I have had, for some time, a friend with an original PC7300, and yes he paid the original retail ( less about 10% ). This unit has TWO fans, one on the right side of the case in the rear, and one on the left side. For about the first year, or so, the fans ran at the same slow speed. After that, they started running faster occasionally. My friend removed the case and cleaned out the accumulated dirt. He was very precicse about this (anal retentive) and removed all accessory boards (memory) and used pure spray freon (tuner wash) to remove all traces of dirt and grime, returning the unit to factory new condition. He ALSO CLEANED OUT THE FANS! This unit returned to factory new quiteness. However, he has to repeat this cleaning every 6 months or so ( he does this for obvious reasons, not to quite the fans ) or the fan speed up returns. Neither he nor I have tried to figure out if the speed change takes place in the power supply or if the fans themselves are two speed. It might pay to see if both fans speed up, be he hasn't paid any attention and thats pretty subjective. The service manual mentions only constant voltages of +5, +12 and -12 volts. This seems to imply that the fan speed up is, in fact a quality of the fans themselves. The manual also mentions that the supply is both overvoltage and overcurrent protected and will shut down totally in case of a short, etc. The service manual also reccommends using the fans as a trouble shooting tool as they will not run if the supply is down. You can disconnect everything, and if the fans run, then there is a shorted device in the system (wait a few seconds for the supply to come up as there are delay circuits built in that will remain engaged after a short). This brings up a possible solution. Is it possible, or practical, to add a second fan ala the PC7300? The service manual lists a "Fan Assembly Spares Kit" Com Code 403865272. - Nic