Power Supply fan stopped blowing!
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From: Bob on 14 Jan 2010 23:39 I just installed a new ATX Power Supply, 275 watts, model Silencer by PC Power and Cooling, Inc. It's several years old but never used. The fan was blowing yesterday and sometime in the 8 hours the computer has been running, it stopped. (I turned it off and Im using another computer now. ) I'm running Asus Probe, which monitor fan speeds and temperatures. It says the speed of the "power fan" is zero now. It's been below the threshold speed since yesterday. Is it possible something in or on the mobo could cause the fan not to run? Asus Proble? Did failure to connect it right stop the fan from working, even though the computer is working? Did it just fail, and if I replace it the next one won't? Thanks for any help you can give (The first fan failed because it was 8 years old and maybe because it's a hostile enviorment wth a lot of dust.) I'm running win98SE and XP on the same box and the symptoms are the same in each.
From: Bob on 14 Jan 2010 23:48 On Thu, 14 Jan 2010 23:39:42 -0500, Bob <bob234(a)bigfoot.com> wrote: >I just installed a new ATX Power Supply, 275 watts, model Silencer by >PC Power and Cooling, Inc. It's several years old but never used. > >The fan was blowing yesterday and sometime in the 8 hours the computer >has been running, it stopped. BTW, could this have anything to do with the power supply not being big enough for the load? The power supply which broke was rated 450 watts. I have an Athlon 800 Mhz CPU and one gig, and a 64 meg video card, ATI 7000 series, and not that much else. At leastr I think not.
From: Bob on 15 Jan 2010 00:29 On Thu, 14 Jan 2010 23:39:42 -0500, Bob <bob234(a)bigfoot.com> wrote: > >Is it possible something in or on the mobo could cause the fan not to >run? Asus Proble? > >Did failure to connect it right stop the fan from working, even though >the computer is working? > >Did it just fail, and if I replace it the next one won't? I'm afraid I'll install another one and I'll ruin it too. :) > >Thanks for any help you can give
From: Paul on 15 Jan 2010 00:24 Bob wrote: > On Thu, 14 Jan 2010 23:39:42 -0500, Bob <bob234(a)bigfoot.com> wrote: > >> I just installed a new ATX Power Supply, 275 watts, model Silencer by >> PC Power and Cooling, Inc. It's several years old but never used. >> >> The fan was blowing yesterday and sometime in the 8 hours the computer >> has been running, it stopped. > > BTW, could this have anything to do with the power supply not being > big enough for the load? The power supply which broke was rated 450 > watts. > > I have an Athlon 800 Mhz CPU and one gig, and a 64 meg video card, > ATI 7000 series, and not that much else. At leastr I think not. +5V @ 30A. +12V @ 10A, -5V @ 0.3A, -12V @ 1A, +3.3V @ 14A, +5VSB @ 2A http://web.archive.org/web/20010111100100/pcpowerandcooling.com/products/power_supplies/ultra_quiet/silencers/index_ultraquiet_atx.htm I can't find a picture of the supply. Some supplies have a "fan curve" printed on the side, intended to indicate whether the fan shuts off if the unit is cool enough. Some fan profiles are set up, such that the fan spins at a low constant speed, when the inside of the PSU is cool enough. Others are set up, such that the fan can stop, if the power dissipation is not too great. On some dual fan units, the external facing fan may continue to run, while the internal fan remains stopped most of the time. So policies vary, as to how the fan can behave. The above power supply is 70% efficient. If the power drawn was 150W (gaming mode), 150/0.70 = 214W total. Of that, 150W is dissipated by the load, while 214-150 = 64 watts is waste heat from the power supply. That should be enough heat to require the fan to remain on. Convection wouldn't be sufficient to handle that. If the computer case has a powerful exhaust fan, with the PSU fan stopped, a sneak air path through the power supply, may cause the power supply to be cooled by the main cooling fan on the computer case itself. If it was an 80%+ efficient PSU, I might understand the fan going off, but at 70% efficient, it seems a little less likely. The other question is, what is the idling power of a computer with an Athlon 800 in it. I don't know the answer to that. Athlon processors don't have Cool N' Quiet, but they do have Halt and some kind of Bus Disconnect ("Stop Grant"?), which are lower power states. So there is some opportunity for power saving, but perhaps not as great as more modern processors. My last two processors draw about 12W at idle. And with that low a power draw for the processor, I suppose a fan could switch off on the PSU. ******* The fan in the PSU, can only be monitored if the power supply has a two wire cable with a three hole connector on the end. That allows the fan inside the PSU to be monitored, when the cable is connected to a monitored fan header on the motherboard. The hardware monitor chip, measures the period of time between two successive pulses from the fan RPM signal. Taking the inverse of that time period, gives the RPM rate. The time is measured by a register that counts clock ticks. If the register is "full", then the monitoring circuit has come upon a fan rotation rate which is too low to be measured. The monitor doesn't know if the fan is 300RPM or 0 RPM, since the register has overflowed, and it isn't possible for the hardware to say what happened. As a result, the BIOS (or Asus Probe), could sound an alarm or give an indication that the fan has stopped. Some Asus boards have a fairly high threshold. My old P4 board, registers "0 RPM" when any fan falls below 1800RPM. If I use Speedfan, Speedfan can reprogram the divider in the hardware monitor chip, and monitor fan speeds as low as perhaps 700RPM or so. In that case, it is the BIOS not using the proper divider setting, that makes the hardware monitor a bit on the useless side. ****** Take the side off your PC, and place your hand on the side of the power supply. If the power supply is cool to the touch and the fan is stopped, then presumably all is still well. IF the power supply is scalding hot, then you know the fan has actually failed (or the cable has fallen off inside) and you should not continue to use the supply until it is fixed. Most supplies will have some kind of overtemperature circuit, so that the supply will eventually switch off if it is too hot. Some power supplies, use a connector for the internal cooling fan. So you can actually change out the fan, without needing a soldering iron or without touching the electronics inside. There are dangerous voltages inside, so if you take it apart, try not to touch anything except for the fan connector. I've changed the fan in one power supply here (it was on a Macintosh computer). It would have been hard to get an exact replacement for that old Mac, so I decided to swap the fan out and see if it all held together. I don't use the machine any more, but the fan surgery appears to be OK. I changed all the fans in that computer, because they were getting pretty noisy and obnoxious. If a fan power cable is soldered into the PCB of the power supply, then replacing the fan (if that was what was needed), would be a lot more dangerous. The main capacitor in the power supply has a bleeder resistor, to remove the dangerous voltage on the cap, but you never trust a bleeder to be working (if you expect to remain safe). Some capacitors contain so much energy, that you should not throw a dead short across them (the noise is deafening). A high value resistor (like the bleeder) should be used, to drain the cap over a 30 second period. Even when a cap is "bled", if you come back in five minutes, you can find more voltage on it, so you still have to be careful. I've only been thrown across the room by high voltage once, and it is a great learning experience. One minute you're here - the next you're there - and you can't figure out how you got there. Paul
From: Paul on 15 Jan 2010 00:58
Bob wrote: > On Thu, 14 Jan 2010 23:39:42 -0500, Bob <bob234(a)bigfoot.com> wrote: > >> Is it possible something in or on the mobo could cause the fan not to >> run? Asus Proble? >> >> Did failure to connect it right stop the fan from working, even though >> the computer is working? >> >> Did it just fail, and if I replace it the next one won't? > > I'm afraid I'll install another one and I'll ruin it too. :) >> Thanks for any help you can give > Not likely to happen. Few modern PSUs have fan monitor cables, and all you have is the normal power cables to deal with. You won't ruin a new one. Paul |