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#1
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Trying to replace fans in a power supply
The fans were getting real noisy so I decided to replace the two 80mm 12V
fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? thanks |
#2
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Trying to replace fans in a power supply
Mike wrote:
The fans were getting real noisy so I decided to replace the two 80mm 12V fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? thanks Did you check the old fan with the 9V battery ? Since you say the old fan was still working, but noisy, it should pass the 9V test as well. Always be careful with the polarity when using the battery method. By reversing the wiring on the new fan (black to red), you may have damaged it. I don't see a particular reason a power supply would care, but fans come in several types. If you buy a "case fan", it typically has two wires. Red and black go to +12V and GND (assuming it is a 12V fan and not some other voltage). At least the black color should be the ground, leaving the other color as the more positive connection. The next type, is the three wire fan. The third wire is for tachometer readout. But a PSU doesn't particularly care about RPMs. I have one power supply here, where they include a "sensor" cable, so the RPM signal from the fan can be connected to the motherboard fan header (I can read out the power supply RPMs as a result.) But the power supply itself, is probably not monitoring RPMs (it costs too much to bother). Another kind of three wire fan, includes a different signal on the third wire. Instead of a constantly pulsing signal, they put a logic signal called "locked rotor". If the fan detects that it is below a certain number of RPMs, the signal changes state. So that flavor of fan, has a signal that is "go/no-go" for the connected equipment. Such fans are included on "classy" equipment, such as lab equipment perhaps. Locked rotor would normally be a non pulsing signal, and stays in one state most of the time. So you have some steps to carry out, as part of your repair work. One is, to put the original fan back, and test that the power feeding the fan is still present. You also need to retest the replacement fans, to see if they're damaged by the reverse polarity. The company making the fans, doesn't usually go out of their way, to include a polarity reversal protection diode. (I haven't tested my fans, by reversing the polarity, so I can't tell you whether they'd be damaged or not. There can be either a chip inside the fan hub, or at least a couple transistors, so in fact not all fans have exactly the same design or components inside the hub.) A power supply can be "bench tested", before being placed back in the computer. For example, get a copy of the ATX standards for power supplies. Connect "PS_ON#" to COM or ground. When the power supply is plugged in and the switch on the back of the supply is "ON", the missing step is to connect a paper clip or jumper wire, from PS_ON# to COM. Having the cover in place on the power supply, protects you in the event that the main cap exploded. (Not that this is likely to happen, but the cap does hold a lot of energy. It is also charged to a lethal voltage when operating.) In a previous post I made on the subject, someone suggested that it is wise to always have a slight load on the supply. If you have a couple old hard drives you are no longer using, you might consider connecting them to the 1x4 Molex hard drive connectors. That would provide a very small amount of loading, about 5V @ 1A and 12V @ 0.6A or less. A couple of drives would double that load, to 2A and 1.2A. Some supplies actually have a minimum loading spec, printed on the label, and if your "dummy load" is not meeting the minimum stated value, then you'd look for another way to meet the minimum load. I have a load box for testing power supplies, that I built myself. I bought about $50+ of power resistors from the only good electronics store in town. They also had Mini-Fit Jr. crimp pins, so I could make a connector assembly. I included a fan in my load box as well, to blow over the power resistors. The box might draw about 100W or so, which is pretty small as loads go. The load box has a switch, which connects PS_ON# to COM. Using a box like that, I can test a new supply, before using it on a new build. I can connect my multimeter and verify the voltages under that 100W load. At least I can determine whether the supply is way off, on one of the output rails, before connecting an expensive motherboard. I've only ever replaced one fan on a supply, and the only reason for doing it, was the supply was from an old Macintosh computer. Like yours, the fan was noisy. Fortunately, the fan had the standard three pin connector on the end, so removing the old and inserting the new, was easy. The three pin header inside the supply, had the standard keying scheme, but I also verified that the wire color scheme on the old fan, the voltage etc, also matched, before doing it. For PC supplies, I'd just buy a new one. But for that Mac, finding something with the right power connector pinout, would have been a hassle. Probably nothing but pulls would have been available. Some power supply specs can be found here. The oldest spec is for a 20 pin supply which still has -5V. The second is for 20 pin supply, where the -5V has been removed. The third, is for a 24 pin supply, where the extra pins provide more current flow for some of the rails. You can find the color and location of PS_ON# in these docs. http://web.archive.org/web/200304240...12V_PS_1_1.pdf http://www.formfactors.org/developer...X12V_1_3dg.pdf http://www.formfactors.org/developer...public_br2.pdf Working inside a power supply, should only be attempted if you know what all the potential risks are. In my case, since the old fan could be unplugged, I didn't need to take the supply apart, and expose any of the high voltage areas. Otherwise, I might have just bolted the whole thing back together, and lived with the fan noise. Did I mention I don't really like high voltage ? Or getting shocks ? :-) The purpose of giving warnings, to stay out of power supplies, is some day, we're going to read in the newspaper, where someone was killed, because of advice given. And we definitely don't want that. It is not like you'd be posting back, if you were killed. Another reason the replacement fan might not have worked, is the PSU can use variable voltage to feed the fan. When the PSU is cool, at startup, it might deliver 7V to the fan wires. As the internal component temperature rises, the voltage is increased, to make the fan spin faster. It could be, that the new fan and old fan have a difference in the minimum starting voltage. For example, the other day, I saw a fan spec, where 10.8V was listed as the minimum starting voltage. There are some other 12V fans, that will start with as little as 5V present. Fans also have different air moving capacities, measured in CFM. Roughly speaking, fans comes in low, medium, high, and ultra ratings. When replacing a fan, you want to try to match the characteristics of the original fan. HTH, Paul |
#3
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Trying to replace fans in a power supply
Try the old fans back is one thing you could do. If the fan worked on a 8V battery but not in the power supply that leaves the new fan or power supply at fault and doing this will point you to the culprit. It may be a good idea to compare both plugs on the end of both the fans... in case you are plugging it into a three pin socket and one of the connections are wrong. Some fans as you may know have three wires and not two. davy |
#4
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Trying to replace fans in a power supply
Paul wrote in :
Mike wrote: The fans were getting real noisy so I decided to replace the two 80mm 12V fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? thanks Did you check the old fan with the 9V battery ? Since you say the old fan was still working, but noisy, it should pass the 9V test as well. Always be careful with the polarity when using the battery method. By reversing the wiring on the new fan (black to red), you may have damaged it. I don't see a particular reason a power supply would care, but fans come in several types. If you buy a "case fan", it typically has two wires. Red and black go to +12V and GND (assuming it is a 12V fan and not some other voltage). At least the black color should be the ground, leaving the other color as the more positive connection. The next type, is the three wire fan. The third wire is for tachometer readout. But a PSU doesn't particularly care about RPMs. I have one power supply here, where they include a "sensor" cable, so the RPM signal from the fan can be connected to the motherboard fan header (I can read out the power supply RPMs as a result.) But the power supply itself, is probably not monitoring RPMs (it costs too much to bother). Another kind of three wire fan, includes a different signal on the third wire. Instead of a constantly pulsing signal, they put a logic signal called "locked rotor". If the fan detects that it is below a certain number of RPMs, the signal changes state. So that flavor of fan, has a signal that is "go/no-go" for the connected equipment. Such fans are included on "classy" equipment, such as lab equipment perhaps. Locked rotor would normally be a non pulsing signal, and stays in one state most of the time. So you have some steps to carry out, as part of your repair work. One is, to put the original fan back, and test that the power feeding the fan is still present. You also need to retest the replacement fans, to see if they're damaged by the reverse polarity. The company making the fans, doesn't usually go out of their way, to include a polarity reversal protection diode. (I haven't tested my fans, by reversing the polarity, so I can't tell you whether they'd be damaged or not. There can be either a chip inside the fan hub, or at least a couple transistors, so in fact not all fans have exactly the same design or components inside the hub.) A power supply can be "bench tested", before being placed back in the computer. For example, get a copy of the ATX standards for power supplies. Connect "PS_ON#" to COM or ground. When the power supply is plugged in and the switch on the back of the supply is "ON", the missing step is to connect a paper clip or jumper wire, from PS_ON# to COM. Having the cover in place on the power supply, protects you in the event that the main cap exploded. (Not that this is likely to happen, but the cap does hold a lot of energy. It is also charged to a lethal voltage when operating.) In a previous post I made on the subject, someone suggested that it is wise to always have a slight load on the supply. If you have a couple old hard drives you are no longer using, you might consider connecting them to the 1x4 Molex hard drive connectors. That would provide a very small amount of loading, about 5V @ 1A and 12V @ 0.6A or less. A couple of drives would double that load, to 2A and 1.2A. Some supplies actually have a minimum loading spec, printed on the label, and if your "dummy load" is not meeting the minimum stated value, then you'd look for another way to meet the minimum load. I have a load box for testing power supplies, that I built myself. I bought about $50+ of power resistors from the only good electronics store in town. They also had Mini-Fit Jr. crimp pins, so I could make a connector assembly. I included a fan in my load box as well, to blow over the power resistors. The box might draw about 100W or so, which is pretty small as loads go. The load box has a switch, which connects PS_ON# to COM. Using a box like that, I can test a new supply, before using it on a new build. I can connect my multimeter and verify the voltages under that 100W load. At least I can determine whether the supply is way off, on one of the output rails, before connecting an expensive motherboard. I've only ever replaced one fan on a supply, and the only reason for doing it, was the supply was from an old Macintosh computer. Like yours, the fan was noisy. Fortunately, the fan had the standard three pin connector on the end, so removing the old and inserting the new, was easy. The three pin header inside the supply, had the standard keying scheme, but I also verified that the wire color scheme on the old fan, the voltage etc, also matched, before doing it. For PC supplies, I'd just buy a new one. But for that Mac, finding something with the right power connector pinout, would have been a hassle. Probably nothing but pulls would have been available. Some power supply specs can be found here. The oldest spec is for a 20 pin supply which still has -5V. The second is for 20 pin supply, where the -5V has been removed. The third, is for a 24 pin supply, where the extra pins provide more current flow for some of the rails. You can find the color and location of PS_ON# in these docs. http://web.archive.org/web/200304240...factors.org/de veloper/specs/atx/ATX_ATX12V_PS_1_1.pdf http://www.formfactors.org/developer...X12V_1_3dg.pdf http://www.formfactors.org/developer...2_public_br2.p df Working inside a power supply, should only be attempted if you know what all the potential risks are. In my case, since the old fan could be unplugged, I didn't need to take the supply apart, and expose any of the high voltage areas. Otherwise, I might have just bolted the whole thing back together, and lived with the fan noise. Did I mention I don't really like high voltage ? Or getting shocks ? :-) The purpose of giving warnings, to stay out of power supplies, is some day, we're going to read in the newspaper, where someone was killed, because of advice given. And we definitely don't want that. It is not like you'd be posting back, if you were killed. Another reason the replacement fan might not have worked, is the PSU can use variable voltage to feed the fan. When the PSU is cool, at startup, it might deliver 7V to the fan wires. As the internal component temperature rises, the voltage is increased, to make the fan spin faster. It could be, that the new fan and old fan have a difference in the minimum starting voltage. For example, the other day, I saw a fan spec, where 10.8V was listed as the minimum starting voltage. There are some other 12V fans, that will start with as little as 5V present. Fans also have different air moving capacities, measured in CFM. Roughly speaking, fans comes in low, medium, high, and ultra ratings. When replacing a fan, you want to try to match the characteristics of the original fan. Useful information about pinouts, power supplies and building a load box too. Thanks Paul. I was unaware that PC fans were sensitive to polarity but on reflection it makes sense since I assume they use a brushless motor in order to avoid arching. To the OP: A Digital Multimeter will indicate true negative in it's display regardless of probe orientation so there's no guessing about wire color in relation to D.C. polarity. As an alternative to building the load box Paul describes you could use a PSU tester: http://www.newegg.com/Product/Produc...82E16899705003 Such a tester doesn't provide provide a full load test but will provide a quick and convient test for functionality. -- pcbldrNinetyEight |
#5
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Trying to replace fans in a power supply
pcbldrNinetyEight wrote:
Paul wrote in : Mike wrote: The fans were getting real noisy so I decided to replace the two 80mm 12V fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? thanks Did you check the old fan with the 9V battery ? Since you say the old fan was still working, but noisy, it should pass the 9V test as well. Always be careful with the polarity when using the battery method. By reversing the wiring on the new fan (black to red), you may have damaged it. I don't see a particular reason a power supply would care, but fans come in several types. If you buy a "case fan", it typically has two wires. Red and black go to +12V and GND (assuming it is a 12V fan and not some other voltage). At least the black color should be the ground, leaving the other color as the more positive connection. The next type, is the three wire fan. The third wire is for tachometer readout. But a PSU doesn't particularly care about RPMs. I have one power supply here, where they include a "sensor" cable, so the RPM signal from the fan can be connected to the motherboard fan header (I can read out the power supply RPMs as a result.) But the power supply itself, is probably not monitoring RPMs (it costs too much to bother). Another kind of three wire fan, includes a different signal on the third wire. Instead of a constantly pulsing signal, they put a logic signal called "locked rotor". If the fan detects that it is below a certain number of RPMs, the signal changes state. So that flavor of fan, has a signal that is "go/no-go" for the connected equipment. Such fans are included on "classy" equipment, such as lab equipment perhaps. Locked rotor would normally be a non pulsing signal, and stays in one state most of the time. So you have some steps to carry out, as part of your repair work. One is, to put the original fan back, and test that the power feeding the fan is still present. You also need to retest the replacement fans, to see if they're damaged by the reverse polarity. The company making the fans, doesn't usually go out of their way, to include a polarity reversal protection diode. (I haven't tested my fans, by reversing the polarity, so I can't tell you whether they'd be damaged or not. There can be either a chip inside the fan hub, or at least a couple transistors, so in fact not all fans have exactly the same design or components inside the hub.) A power supply can be "bench tested", before being placed back in the computer. For example, get a copy of the ATX standards for power supplies. Connect "PS_ON#" to COM or ground. When the power supply is plugged in and the switch on the back of the supply is "ON", the missing step is to connect a paper clip or jumper wire, from PS_ON# to COM. Having the cover in place on the power supply, protects you in the event that the main cap exploded. (Not that this is likely to happen, but the cap does hold a lot of energy. It is also charged to a lethal voltage when operating.) In a previous post I made on the subject, someone suggested that it is wise to always have a slight load on the supply. If you have a couple old hard drives you are no longer using, you might consider connecting them to the 1x4 Molex hard drive connectors. That would provide a very small amount of loading, about 5V @ 1A and 12V @ 0.6A or less. A couple of drives would double that load, to 2A and 1.2A. Some supplies actually have a minimum loading spec, printed on the label, and if your "dummy load" is not meeting the minimum stated value, then you'd look for another way to meet the minimum load. I have a load box for testing power supplies, that I built myself. I bought about $50+ of power resistors from the only good electronics store in town. They also had Mini-Fit Jr. crimp pins, so I could make a connector assembly. I included a fan in my load box as well, to blow over the power resistors. The box might draw about 100W or so, which is pretty small as loads go. The load box has a switch, which connects PS_ON# to COM. Using a box like that, I can test a new supply, before using it on a new build. I can connect my multimeter and verify the voltages under that 100W load. At least I can determine whether the supply is way off, on one of the output rails, before connecting an expensive motherboard. I've only ever replaced one fan on a supply, and the only reason for doing it, was the supply was from an old Macintosh computer. Like yours, the fan was noisy. Fortunately, the fan had the standard three pin connector on the end, so removing the old and inserting the new, was easy. The three pin header inside the supply, had the standard keying scheme, but I also verified that the wire color scheme on the old fan, the voltage etc, also matched, before doing it. For PC supplies, I'd just buy a new one. But for that Mac, finding something with the right power connector pinout, would have been a hassle. Probably nothing but pulls would have been available. Some power supply specs can be found here. The oldest spec is for a 20 pin supply which still has -5V. The second is for 20 pin supply, where the -5V has been removed. The third, is for a 24 pin supply, where the extra pins provide more current flow for some of the rails. You can find the color and location of PS_ON# in these docs. http://web.archive.org/web/200304240...factors.org/de veloper/specs/atx/ATX_ATX12V_PS_1_1.pdf http://www.formfactors.org/developer...X12V_1_3dg.pdf http://www.formfactors.org/developer...2_public_br2.p df Working inside a power supply, should only be attempted if you know what all the potential risks are. In my case, since the old fan could be unplugged, I didn't need to take the supply apart, and expose any of the high voltage areas. Otherwise, I might have just bolted the whole thing back together, and lived with the fan noise. Did I mention I don't really like high voltage ? Or getting shocks ? :-) The purpose of giving warnings, to stay out of power supplies, is some day, we're going to read in the newspaper, where someone was killed, because of advice given. And we definitely don't want that. It is not like you'd be posting back, if you were killed. Another reason the replacement fan might not have worked, is the PSU can use variable voltage to feed the fan. When the PSU is cool, at startup, it might deliver 7V to the fan wires. As the internal component temperature rises, the voltage is increased, to make the fan spin faster. It could be, that the new fan and old fan have a difference in the minimum starting voltage. For example, the other day, I saw a fan spec, where 10.8V was listed as the minimum starting voltage. There are some other 12V fans, that will start with as little as 5V present. Fans also have different air moving capacities, measured in CFM. Roughly speaking, fans comes in low, medium, high, and ultra ratings. When replacing a fan, you want to try to match the characteristics of the original fan. Useful information about pinouts, power supplies and building a load box too. Thanks Paul. I was unaware that PC fans were sensitive to polarity but on reflection it makes sense since I assume they use a brushless motor in order to avoid arching. To the OP: A Digital Multimeter will indicate true negative in it's display regardless of probe orientation so there's no guessing about wire color in relation to D.C. polarity. As an alternative to building the load box Paul describes you could use a PSU tester: http://www.newegg.com/Product/Produc...82E16899705003 Such a tester doesn't provide provide a full load test but will provide a quick and convient test for functionality. I provided some info here, to help someone build a load box. The hardest part is finding the Mini-fit Jr. pins, and I was surprised my electronics store had them. I don't think they carry them any more. Digikey and Mouser are possible sources on the net. http://groups.google.ca/group/alt.co...b?dmode=source Good power resistors can be hard to find, and the best ones are typically surplus. An example here. I've used this style before. But if you need a handful of these for a project, the price adds up fast. I think I've even got some of these from surplus sources (when I was a kid). There are other form factors for about half the price. http://www.newark.com/01F9750/passiv...H-25-5R000-1.0 http://www.newark.com/28K6272/passiv...TICOMP-MC14658 Paul |
#6
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Trying to replace fans in a power supply
Paul wrote:
.... snip ... Good power resistors can be hard to find, and the best ones are typically surplus. An example here. I've used this style before. But if you need a handful of these for a project, the price adds up fast. I think I've even got some of these from surplus sources (when I was a kid). There are other form factors for about half the price. Old fashioned incandescent light bulbs are a useful substitute. The wattage is written on them :-) Derate by at least 50%, and measure the resistance. -- [mail]: Chuck F (cbfalconer at maineline dot net) [page]: http://cbfalconer.home.att.net Try the download section. -- Posted via a free Usenet account from http://www.teranews.com |
#7
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Trying to replace fans in a power supply
Mike wrote: The fans were getting real noisy so I decided to replace the two 80mm 12V fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? Most PSUs apply as little as 6V to the fans when the PSU is cool, but some fans won't spin at that voltage. So test the fans with +5V from the PSU (red and black wires of the PSU). If they spin, even if you give them a push, then they should be OK. |
#8
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Trying to replace fans in a power supply
On Sat, 23 Feb 2008 18:41:53 -0800, "Mike"
wrote: The fans were getting real noisy so I decided to replace the two 80mm 12V fans. I bought two 12V fans and replaced the old ones making sure I hooked up the right colored wires together, black to black and red to red. For some reason neither fans worked when I turned on the computer. The computer turned on without any problems. I tested the new fans with a 9 volt battery and they worked. I even tried reversing the wiring (black to red, black to red) without any luck. Anybody know how I can get these fans to work? thanks If these fans are very low RPM, a PSU with a fan control circuit may not apply enough voltage to spin them until it gets hot. If the fan have an onboard fan control circuit themselves in addtion to a fan control circuit in the PSU this will also keep them from working until quite hot. The solution to either is to use different fans, short out the thermal control (diode or thermistor) on the fan if it's accessible (soldering the two ends of the sensor together), or wire the fan direct to the 12V rail instead of through the fan control circuit, fan header. |
#9
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Trying to replace fans in a power supply
I just checked the old and new fans with a 9 volt battery and they all work.
I put the old fans back in the PS and they worked. The circuit boards on all 4 fans are encased in plastic so there in no way to get to them. I am thinking the fans are proprietary to this PS. In order to replace the fans the circuit boards have to be the same. The label on the PS says "with Fan Sensor Control", whatever that means. The PS isnt an Antec or top of the line but it does a great job. There is no way I can use the old fans, way too noisy. There has to be a way to wire these new fans so they always stay on when the computer is on |
#10
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Trying to replace fans in a power supply
A new discovery, I shorted the green and black pins with a wire so I can
turn on the PS outside of the case. I found out the new fans work outside of the case. So there must be something thats preventing the fans from working when everything is hooked up in the computer. Any ideas? "Mike" wrote in message ... I just checked the old and new fans with a 9 volt battery and they all work. I put the old fans back in the PS and they worked. The circuit boards on all 4 fans are encased in plastic so there in no way to get to them. I am thinking the fans are proprietary to this PS. In order to replace the fans the circuit boards have to be the same. The label on the PS says "with Fan Sensor Control", whatever that means. The PS isnt an Antec or top of the line but it does a great job. There is no way I can use the old fans, way too noisy. There has to be a way to wire these new fans so they always stay on when the computer is on |
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