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#1
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PSU question
Just bought a new PSU, a Coolermaster iGreen 500W one. Wanting to test it I
plugged it in and nothing happened. Should PSUs work when not connected to a motherboard? I test Cisco PSUs like this all the time, so expected this to work. Duff item or should I just wait till my motherboard arrives? Cheers. |
#2
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PSU question
"MA" wrote in message ... Just bought a new PSU, a Coolermaster iGreen 500W one. Wanting to test it I plugged it in and nothing happened. Should PSUs work when not connected to a motherboard? I test Cisco PSUs like this all the time, so expected this to work. Duff item or should I just wait till my motherboard arrives? Cheers. The motherboard and PSU work together. Power switch (momentary contact) connects through mainboard. When you short that switch (push the button), mainboard passes through request to power supply to turn on. Then power supply turns on, and (if OK) sends power OK signal back to mainboard. When power OK signal is received, CPU wakes up and attempts to run POST program stored in mainboard BIOS. If POST runs OK, then video card is initialized. After video card is initialized, you should then have "video" on the monitor (possibly showing memory tests and other mainboard information), and the mainboard will look for OS to boot (usually from hard drive). Or the short answer, it's foolish to try to test the power supply without a mainboard, unless you have a power supply tester (they make those) -Dave |
#3
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PSU question
Mike T. wrote:
"MA" wrote in message ... Just bought a new PSU, a Coolermaster iGreen 500W one. Wanting to test it I plugged it in and nothing happened. Should PSUs work when not connected to a motherboard? I test Cisco PSUs like this all the time, so expected this to work. Duff item or should I just wait till my motherboard arrives? Cheers. The motherboard and PSU work together. Power switch (momentary contact) connects through mainboard. When you short that switch (push the button), mainboard passes through request to power supply to turn on. Then power supply turns on, and (if OK) sends power OK signal back to mainboard. When power OK signal is received, CPU wakes up and attempts to run POST program stored in mainboard BIOS. If POST runs OK, then video card is initialized. After video card is initialized, you should then have "video" on the monitor (possibly showing memory tests and other mainboard information), and the mainboard will look for OS to boot (usually from hard drive). Or the short answer, it's foolish to try to test the power supply without a mainboard, unless you have a power supply tester (they make those) -Dave Makes sense! Thanks for the quick and detailed reply. I'm just glad I don't have to find a spare chassis to test our Cisco power supplies every time I need to. |
#4
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PSU question
MA wrote:
Mike T. wrote: "MA" wrote in message ... Just bought a new PSU, a Coolermaster iGreen 500W one. Wanting to test it I plugged it in and nothing happened. Should PSUs work when not connected to a motherboard? I test Cisco PSUs like this all the time, so expected this to work. Duff item or should I just wait till my motherboard arrives? Cheers. The motherboard and PSU work together. Power switch (momentary contact) connects through mainboard. When you short that switch (push the button), mainboard passes through request to power supply to turn on. Then power supply turns on, and (if OK) sends power OK signal back to mainboard. When power OK signal is received, CPU wakes up and attempts to run POST program stored in mainboard BIOS. If POST runs OK, then video card is initialized. After video card is initialized, you should then have "video" on the monitor (possibly showing memory tests and other mainboard information), and the mainboard will look for OS to boot (usually from hard drive). Or the short answer, it's foolish to try to test the power supply without a mainboard, unless you have a power supply tester (they make those) -Dave Makes sense! Thanks for the quick and detailed reply. I'm just glad I don't have to find a spare chassis to test our Cisco power supplies every time I need to. On an ATX supply, connect PS_ON# to an adjacent COM pin. Those signals are on the main power cable. Some people do that with a paper clip. But you should consider placing a dummy load on the supply, to draw a bit of current. The power supply cannot regulate well, if there is no load. Some ATX supplies actually list a minimum current on the label, which is a hint that the regulation will be off. A couple old disk drives, connected to the disk cables, is one way to load an ATX PSU. I've built my own load box, which draws a bit more current. I use a toggle switch between PS_ON# and COM, to make the load box turn the supply on and off. Then, I can probe the output rails and see if they are all reasonably close to the expected values. It'll take about $50-$100 worth of components to make a small load box, with a fan to blow over the resistors to keep them cool. Here is a schematic of an ATX supply: http://www.pavouk.comp.cz/hw/en_atxps.html On the output stage, the diodes can "push" current, but not "pull" current. That is why a bit of loading, constantly "pulling" on the rails, helps to keep the power supply output voltage in the proper range. A power supply may have its own scheme for loading the supply internally, but for maximum testing safety (i.e. do no harm), a dummy load is a good idea. Especially if the supplies are ancient, and not as well designed as modern ones. ******* The latest ATX specs are here - i.e. "ATX12V V2.2" http://www.formfactors.org/devlist.asp?FFID=-1&CatID=2 http://www.formfactors.org/developer...public_br2.pdf Older specs are not listed, but are still hiding on the site. For older computers, the pinout info here may be more appropriate. http://www.formfactors.org/developer...X12V_1_3dg.pdf And this spec is even older. This version has the 1x6 "Aux" connector pinout, if you need it. http://web.archive.org/web/200304240...12V_PS_1_1.pdf ******* Paul |
#5
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PSU question
MA wrote:
Mike T. wrote: "MA" wrote in message ... Just bought a new PSU, a Coolermaster iGreen 500W one. Wanting to test it I plugged it in and nothing happened. Should PSUs work when not connected to a motherboard? I test Cisco PSUs like this all the time, so expected this to work. Duff item or should I just wait till my motherboard arrives? Cheers. The motherboard and PSU work together. Power switch (momentary contact) connects through mainboard. When you short that switch (push the button), mainboard passes through request to power supply to turn on. Then power supply turns on, and (if OK) sends power OK signal back to mainboard. When power OK signal is received, CPU wakes up and attempts to run POST program stored in mainboard BIOS. If POST runs OK, then video card is initialized. After video card is initialized, you should then have "video" on the monitor (possibly showing memory tests and other mainboard information), and the mainboard will look for OS to boot (usually from hard drive). Or the short answer, it's foolish to try to test the power supply without a mainboard, unless you have a power supply tester (they make those) -Dave Makes sense! Thanks for the quick and detailed reply. I'm just glad I don't have to find a spare chassis to test our Cisco power supplies every time I need to. On an ATX supply, connect PS_ON# to an adjacent COM pin. Those signals are on the main power cable. Some people do that with a paper clip. But you should consider placing a dummy load on the supply, to draw a bit of current. The power supply cannot regulate well, if there is no load. Some ATX supplies actually list a minimum current on the label, which is a hint that the regulation will be off. A couple old disk drives, connected to the disk cables, is one way to load an ATX PSU. I've built my own load box, which draws a bit more current. I use a toggle switch between PS_ON# and COM, to make the load box turn the supply on and off. Then, I can probe the output rails and see if they are all reasonably close to the expected values. It'll take about $50-$100 worth of components to make a small load box, with a fan to blow over the resistors to keep them cool. Here is a schematic of an ATX supply: http://www.pavouk.comp.cz/hw/en_atxps.html On the output stage, the diodes can "push" current, but not "pull" current. That is why a bit of loading, constantly "pulling" on the rails, helps to keep the power supply output voltage in the proper range. A power supply may have its own scheme for loading the supply internally, but for maximum testing safety (i.e. do no harm), a dummy load is a good idea. Especially if the supplies are ancient, and not as well designed as modern ones. ******* The latest ATX specs are here - i.e. "ATX12V V2.2" http://www.formfactors.org/devlist.asp?FFID=-1&CatID=2 http://www.formfactors.org/developer...public_br2.pdf Older specs are not listed, but are still hiding on the site. For older computers, the pinout info here may be more appropriate. http://www.formfactors.org/developer...X12V_1_3dg.pdf And this spec is even older. This version has the 1x6 "Aux" connector pinout. http://web.archive.org/web/200304240...12V_PS_1_1.pdf ******* Paul |
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