Top Document: comp.sys.3b1 FAQ part2 Previous Document: 6.2. How do I open the case and get to the motherboard? Next Document: 6.4. Why has my clock stopped? See reader questions & answers on this topic! - Help others by sharing your knowledge The fans have been a problem with the UNIX PC in a lot of cases. What happens is the 12VDC fan is connected to a thermal switch that will run the fan motor faster when the machine is hot, and then slow it down when the machine cools. There have been occasions, however, when a fan goes from fast to slow, and then slows all the way to a dead stop. The fan tends to collect a lot of dust and dirt, and sometimes when switching to the slow speed it goes so slow that it stops and doesn't have enough "umph" to start up again. Gil Kloepfer theorizes the reason for this happening is that the 12VDC fan is constantly running with too little current due to a resistor wired in series with the power supply when the thermal switch is in its normally open position. When the fan is beginning to malfunction, it will run subtly slower, but not enough to keep enough air moving through the machine. The thermal switch kicks-up the power, which causes the fan to move faster and cool the machine down until the switch kicks-out again. This cycling effect keeps going until the fan become excessively weak and clogged with dirt to where it eventually stops working permanently. But he goes on to add that, in any case, "I don't think it's just dirt." The next stage is the machine overheats, the power supply cuts out, and the machine powers down, then it powers up, and down, and up. If you are lucky, you catch this before major damage occurs or you take preventive measures beforehand. Most of the time the power supply gets so hot, it warps the plastic case above it. This is a sure sign that a UNIX PC has had a "meltdown" before. What can you do? Well, you can replace the 12VDC fan with a 3" 120VAC fan. The 120VAC fans are more robust, they produce more air current (~34CFM normally) and don't draw on the power supply any. One drawback is that they are noisier. Radio Shack has an appropriate 120VAC fan for $16.95, cat. no. 273-242. Some people can go years or forever without ever having a problem, but it just takes that one day that you aren't around and the machine goes into "meltdown" and then you'll be assured some damage somewhere. User Contributions:Top Document: comp.sys.3b1 FAQ part2 Previous Document: 6.2. How do I open the case and get to the motherboard? Next Document: 6.4. Why has my clock stopped? Part1 - Part2 - Single Page [ Usenet FAQs | Web FAQs | Documents | RFC Index ] Send corrections/additions to the FAQ Maintainer: jbunch@nyx.nyx.net (John B. Bunch)
Last Update March 27 2014 @ 02:11 PM
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