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Old MOBO, PS and CPU-fan running without start button.
GIGABYTE - Motherboard - Socket 775 - GA-945P-S3 (rev. 1.0)
I have everything disconnected apart the two power connecters. When I turned on/connect the AC, the Power-Supply turns-on and the CPU-fan runs at full speed. Has anybody got an idea why this is happening? |
#2
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Old MOBO, PS and CPU-fan running without start button.
Patrick wrote:
GIGABYTE - Motherboard - Socket 775 - GA-945P-S3 (rev. 1.0) I have everything disconnected apart the two power connecters. When I turned on/connect the AC, the Power-Supply turns-on and the CPU-fan runs at full speed. Has anybody got an idea why this is happening? Look in the "Power Management" section of the BIOS. I have a Gigabyte manual from a 945P motherboard, but not the same one as yours, and the last item in that BIOS section is: AC Back Function Soft-Off When AC-power back to the system, the system will be in "Off" state. [Default value] Full-On When AC-power back to the system, the system always in "On" state. Memory When AC-power back to the system, the system will return to the Last state before AC-power off. I had a BIOS NVRAM setting change the other day, *without* tripping the checksum. And resetting my settings and re-programming the custom ones brought it all back to correct operation. That shouldn't be necessary in your case. Just set it back to the default choice they showed in the manual, the Soft-Off, and retest and make sure it works. Shut down. Shut off AC power at the back. Wait several minutes for the inrush limiter to cool off. Switch on. And if the corrected setting worked... the machine should quietly wait for you without doing a thing. ******* The second possibility, is you've had a hardware failure, or you dropped a tool inside the computer and broke the pullup on the PS_ON# signal and now it's pulling to ground and won't let go. Normally, when PS_ON# control is lost, it's the motherboard end, the transistor is no longer strong enough to pull the signal low and turn on the PSU. But in your case, it would be the opposite scenario. The signal never returns to the de-asserted state ( where +5V appears on PS_ON#). Either a pullup resistor is missing, or the transistor has failed in the ON state. These aren't too likely, unless there's something pretty abnormal going on (like, a leaking electrolytic capacitor spilled orange/brown corrosive liquid on the traces and ruined something). I've only had PSUs do that, no mobos so far. My failures were in my collection of Antec Channelwell ones. (The Antec Delta might well be fine.) Paul |
#3
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Old MOBO, PS and CPU-fan running without start button.
On 23/12/2020 20:44, Paul wrote:
Patrick wrote: GIGABYTE - Motherboard - Socket 775 - GA-945P-S3 (rev. 1.0) I have everything disconnected apart the two power connecters. When I turned on/connect the AC, the Power-Supply turns-on and the CPU-fan runs at full speed. Has anybody got an idea why this is happening? Look in the "Power Management" section of the BIOS. I have a Gigabyte manual from a 945P motherboard, but not the same one as yours, and the last item in that BIOS section is: AC Back Function * Soft-Off** When AC-power back to the system, ************ the system will be in "Off" state.* [Default value] * Full-On*** When AC-power back to the system, ************ the system always in "On" state. * Memory**** When AC-power back to the system, the ************ system will return to the Last state ************ before AC-power off. I had a BIOS NVRAM setting change the other day, *without* tripping the checksum. And resetting my settings and re-programming the custom ones brought it all back to correct operation. That shouldn't be necessary in your case. Just set it back to the default choice they showed in the manual, the Soft-Off, and retest and make sure it works. Shut down. Shut off AC power at the back. Wait several minutes for the inrush limiter to cool off. Switch on. And if the corrected setting worked... the machine should quietly wait for you without doing a thing. ******* The second possibility, is you've had a hardware failure, or you dropped a tool inside the computer and broke the pullup on the PS_ON# signal and now it's pulling to ground and won't let go. Normally, when PS_ON# control is lost, it's the motherboard end, the transistor is no longer strong enough to pull the signal low and turn on the PSU. But in your case, it would be the opposite scenario. The signal never returns to the de-asserted state ( where +5V appears on PS_ON#). Either a pullup resistor is missing, or the transistor has failed in the ON state. These aren't too likely, unless there's something pretty abnormal going on (like, a leaking electrolytic capacitor spilled orange/brown corrosive liquid on the traces and ruined something). I've only had PSUs do that, no mobos so far. My failures were in my collection of Antec Channelwell ones. (The Antec Delta might well be fine.) ** Paul Thanks Paul for your reply . I have machine torn apart at the moment (secondary PC). I connected the PS to AC (without connection to MOBO) and the PS fan was turning. Took the PS apart, noticed a few bulged capacitors, cleaned some dust-bunnies out and put the PS together again. I will (when I get a 'round-tuit') check the voltages coming from the PS, etc. Thanks again Paul for your consideration. |
#4
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Old MOBO, PS and CPU-fan running without start button.
On 23/12/2020 12:53, Patrick wrote:
GIGABYTE - Motherboard - Socket 775 - GA-945P-S3 (rev. 1.0) I have everything disconnected apart the two power connecters. When I turned on/connect the AC, the Power-Supply turns-on and the CPU-fan runs at full speed. Has anybody got an idea why this is happening? I replaced the PS (was due a new one on my primary machine), the MoBo is now working, no HD/SSD connected yet but have access to the BIOS and have several 'Macrium' backups. Thanks Paul (and anyone else) for your interest. |
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