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Possibly Dead P4S8X?
After returning from a camping trip I hit the power button on my
computer. The red light on the front came on but no display. I noticed that the red light is burning solid. I took the cover off the computer and made sure connections were tight. When I power it up a red light on the motherboard flashes once. There is a green light on the motherboard that stays lit. However the onboard fan does not start. The fan on the computer case does work. The last time I used the computer (yesterday) everything was running fine. The computer has a 2.8GhZ P-IV with WinXP Pro 512 MB DDR 120 MB Maxtor 7200 rpm HDD 40 MB Maxtor 7200 rpm HDD Pioneer DVDROM Pioneer DVD-Writer The computer is only about 1.5 years old. Any ideas? Thank you. |
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It sounds like either the power supply unit or the motherboard failed. The
easiest way to see is to try replacing the PSU with a known working one of adequate output. -- DaveW "JPeterman" biteme@thelibrary wrote in message ... After returning from a camping trip I hit the power button on my computer. The red light on the front came on but no display. I noticed that the red light is burning solid. I took the cover off the computer and made sure connections were tight. When I power it up a red light on the motherboard flashes once. There is a green light on the motherboard that stays lit. However the onboard fan does not start. The fan on the computer case does work. The last time I used the computer (yesterday) everything was running fine. The computer has a 2.8GhZ P-IV with WinXP Pro 512 MB DDR 120 MB Maxtor 7200 rpm HDD 40 MB Maxtor 7200 rpm HDD Pioneer DVDROM Pioneer DVD-Writer The computer is only about 1.5 years old. Any ideas? Thank you. |
#3
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In article , awtwtw wrote:
After returning from a camping trip I hit the power button on my computer. The red light on the front came on but no display. I noticed that the red light is burning solid. I took the cover off the computer and made sure connections were tight. When I power it up a red light on the motherboard flashes once. There is a green light on the motherboard that stays lit. However the onboard fan does not start. The fan on the computer case does work. The last time I used the computer (yesterday) everything was running fine. The computer has a 2.8GhZ P-IV with WinXP Pro 512 MB DDR 120 MB Maxtor 7200 rpm HDD 40 MB Maxtor 7200 rpm HDD Pioneer DVDROM Pioneer DVD-Writer The computer is only about 1.5 years old. Any ideas? Thank you. As Dave said, the power supply is always a likely source of failure to boot. But, one of your other symptoms bothers me a bit. The red LED on the motherboard is the "AGP_Warn" circuit. It is supposed to check for an illegal 3.3V only video card, and prevent the computer from starting. If an illegal (improperly keyed) video card is present, the PS_ON# signal is prevented from reaching the power supply, by AGP_Warn. The AGP_Warn has two ingredients. One I have traced down, so I know it is there. The TYPEDET# signal from pin A2 on the video card is connected to one of the transistors. Apparently, if TYPEDET# is grounded, everything is OK. If TYPEDET# floats, then that will cause the red LED to light up. A second ingredient of the check, is the circuit can only stop the power, if an AGP card is inserted. It would be inappropriate for the circuit to light the LED, if no video card is present. So, to do its job, the logic has to be AGP_Present AND TYPEDET#_floating. I don't know what pin is checked to verify the card is present. Now, your symptom of the LED flashing for a moment is weird. The inputs to AGP_Warn are supposed to be static and unchanging. Yet, your AGP_Warn lights for a moment and then stops, and I cannot think of a mechanism for that to happen, unless +5VSB is going out. And, you said the green LED on the motherboard stays lit and the fan runs on the back of the case. That means +5VSB is present and +12V is there to run the fan. If you have another video card compatible with the board, try swapping that in. It could be the video card, but as I say, I cannot really think of a failure mechanism that would cause the LED to light (indicating trouble) and then extinguish, unless all power was being lost at the same time. Paul |
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On Sat, 14 Aug 2004 23:23:58 GMT, "DaveW" wrote:
It sounds like either the power supply unit or the motherboard failed. The easiest way to see is to try replacing the PSU with a known working one of adequate output. Thank you Dave. |
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On Sun, 15 Aug 2004 05:57:28 -0400, (Paul) wrote:
In article , JPeterman biteme@thelibrary wrote: On Sat, 14 Aug 2004 19:55:28 -0400, (Paul) wrote: In article , awtwtw wrote: As Dave said, the power supply is always a likely source of failure to boot. But, one of your other symptoms bothers me a bit. The red LED on the motherboard is the "AGP_Warn" circuit. It is supposed to check for an illegal 3.3V only video card, and prevent the computer from starting. If an illegal (improperly keyed) video card is present, the PS_ON# signal is prevented from reaching the power supply, by AGP_Warn. The AGP_Warn has two ingredients. One I have traced down, so I know it is there. The TYPEDET# signal from pin A2 on the video card is connected to one of the transistors. Apparently, if TYPEDET# is grounded, everything is OK. If TYPEDET# floats, then that will cause the red LED to light up. A second ingredient of the check, is the circuit can only stop the power, if an AGP card is inserted. It would be inappropriate for the circuit to light the LED, if no video card is present. So, to do its job, the logic has to be AGP_Present AND TYPEDET#_floating. I don't know what pin is checked to verify the card is present. Now, your symptom of the LED flashing for a moment is weird. The inputs to AGP_Warn are supposed to be static and unchanging. Yet, your AGP_Warn lights for a moment and then stops, and I cannot think of a mechanism for that to happen, unless +5VSB is going out. And, you said the green LED on the motherboard stays lit and the fan runs on the back of the case. That means +5VSB is present and +12V is there to run the fan. If you have another video card compatible with the board, try swapping that in. It could be the video card, but as I say, I cannot really think of a failure mechanism that would cause the LED to light (indicating trouble) and then extinguish, unless all power was being lost at the same time. Paul Firstly let me thank you for your detailed response. Most of this was over my head but I understand the gist of it. The power button on the front of the case will not turn the power off. I have to hit the switch on the back. I just tried it again and the red LED on the motherboard will not flash at all. I forgot that there is a voice "post reporter" at boot that may tell me something. I didn't have the speakers on when this happened so I'm going to try it. So the power supply may be suspect even though it powers the other two fans? I don't have another video card but I have been leaning towards getting another one. Thanks again for your patience and time. Your observation that the switch on the back is needed for control changes things a bit. The PSU has several output voltages. Perhaps only one of them is not working, and the others are. If you own a voltmeter, you can take a disk drive power connector in hand, and check for +5V and +12V. If the PSU has a six pin Aux power connector, there will be a +3.3V pin on it. Those are the major voltages, and I don't know if the motherboard depends on -5V and -12V in any meaningful way or not. On my P4C800-E for example, -12V is used by the serial port, so if -12V dies, my serial port will die, but the rest of the board will still run. It could be your PSU has lost +3.3V or +5V. When using your voltmeter, connect the black lead to a lug on one of the connectors on the back of the computer. I'm assuming you have some alligator clips or another clever way to connect it. The reason is, you don't want to accidently touch the two voltmeter leads together while working on the power supply. I find with one red lead in my hand, things are much safer. It is like safety rules for jumpering car batteries - there is a lot of available current there if you make a mistake. I think as Dave said, I'd try a PSU swap first. If the result is that the red LED stays on, borrow another video card, to see if it will go off again. If the red LED stays on even with another video card, it is time to RMA the motherboard. The AGP_Warn circuit has failed on some motherboards out of the box, but I've never heard of one dying on a system that was working for a while. Your AGP_Warn is just another mystery for the books :-) I haven't traced the whole circuit, and as those SMT components are so hard to identify, I probably never will finish it. HTH, Paul Since I don't have a voltmeter or another video card I think I''m going to buy another power supply. The one I have is a Duro 400 watt supply so I probably won't buy one of these. If that fails to correct the situation I'' buy a new video card. Thanks for all of your help. I've got a lot more insight for the future. |
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