Power SW pins not always have power.

DiaNo

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Oct 18, 2022
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The PC : Acer aspire M5700, Windows 7 Pro. 32b.
Intel® Core™2 Quad CPU,DDR2 800 SDRAM 4G,GPU has been removed & use on board Intel® G45,G45T AM2 V:1.0 motherboard,Hitachi SATA2 3.0Hb/s 7200rpm 500GB, Labelflash DVD SuperMulti DL optical drive。
Items removed: Floppy disc drive, GPU, & rear wall fan.
History:
The original PC had 2 G DRAM & SATA2 HD 320G & Win Vista. I increased DRAM to 8 G & replaced the HDD with a Hitachi SATA2 3.0Hb/s 7200rpm 500GB & installed Win 7 Pro. 32b.

For the first 4 years 2009~2013, the PC was used only for post-processing photographs. 2013~2015, it was a standby PC.
In 2016, GPU & Floppy drive & fan on the rear wal were removed & the PC became a warehouse of photographs.

A few months ago, it started an issue: could not start normally, had to tap on the switch a few times.

Now, there is no tell whether it will start if the switch is tappied a hundred times.

Three weeks ago, I had the PC disassembled & cleaned. It started a few times after reassembling. It won't start now.

Have tried to short the Power SW pins. There is no poswer on these pins or they are malfunctioning.

Tested the PSU, with a wire insert in to power supply connectors, 4 the green wire & 5 the black wire, to see if the PSU fan would run. It rans. Tested 3 times. The PSU supplies power.

But the Power SW pins either do not have power or are malfunctioning.

Help, please?

Thanks.
DiaNo
 
Sounds like the motherboard could be dying if the power sw pins aren't working. Or there could be a short or other problem, try pulling power, plug in again, and hit power sw once. Does anything at all happen? A fan twitch/spin, led lights, anything?

If yes, there's a problem somewhere, pull everything but 1 ram and cpu. Still no go, board is bricked.

If no, board is bricked. Probably.

A multimeter would be good to test the PSU and motherboard. Test 12V, 5V, 3.3V, etc..

Look for swollen capacitors on the board too, that is around the time where it was common, they would have degrading startup issues too.
 
Sounds like the motherboard could be dying if the power sw pins aren't working. Or there could be a short or other problem, try pulling power, plug in again, and hit power sw once. Does anything at all happen? A fan twitch/spin, led lights, anything?

If yes, there's a problem somewhere, pull everything but 1 ram and cpu. Still no go, board is bricked.

If no, board is bricked. Probably.

A multimeter would be good to test the PSU and motherboard. Test 12V, 5V, 3.3V, etc..

Look for swollen capacitors on the board too, that is around the time where it was common, they would have degrading startup issues too.
Thank you.

Read your instructions 2 days ago and tested accordingly.

Test l.
"try pulling power, plug in again, and hit power sw once. Does anything at all happen? A fan twitch/spin, led lights, anything?
No. Nothing happens. No twitch, no light, nothing.
Test with peripherals connected. Nothing happens.
Test without peripherals. Nothing happens.

But, test without peripherals, after ten or twenty taps on the start switch, the PC starts, LED lights are on, CPU fan turns, and a normal "B" beeps.
This pappens only once during this test. Wont happen no matter how many times the start swith is tapped.


Test 2.
"pull everything but 1 ram and cpu. Still no go, board is bricked."
Yes. It does, but...
A. Tap on start switch, it starts with a normal beep. Let it run for ten minutes. Press & hold start switch to shut down.
B. A moment later, tap on start switch, it starts with a normal beep. Have HDD, Keyboard, Mouse, Monitor, & internet cable connected. Shut it down.
C. About 2 minutes later, tap on the start switch, one tap on the start switch, it started. Let it run for about one hour. Shut it down by Windows.
D. About 20 minutes later, tap on the start switch, it won't start. Quick tapping 10 or 15 times, it starts. Everything is normal. Runs 2 hours. Shut it down by Windows.
E. One hour & 15 minutes later, tap on start switch, no response. It starts after 40 or 50 taps. Runs a few hours normally for 2 hours. Shut it down by Windows.
Note:
The results of Test 2 are very similar to what happened in the last three weeks as I monkeyed on the PC.
(a). After the PC was reassembled, it started and died off in the same manner.
(b). After testing the PSU, started 3 times, then died.
(c). After the 2nd PSU test, started 2 times, then died.

3."Look for swollen capacitors"
On board and in the PSU, I do not see any round head or barrel belly capacitors. There might be, but I cannot tell if they are not way out of their shape.

So, what is the verdict, please?

Thank you.
 
Have you tried shorting the power sw pins in your testing since? The power button can break, as well as the wiring and pin connector causing unreliability.

Might want to leave it on, use sleep mode for now if it runs stable when on. Bios often have Wake On X commands, like LAN, key press.
 
Have you tried shorting the power sw pins in your testing since? The power button can break, as well as the wiring and pin connector causing unreliability.

Might want to leave it on, use sleep mode for now if it runs stable when on. Bios often have Wake On X commands, like LAN, key press.
Thank you again.

"Have you tried shorting the power sw pins in your testing since?"
Here is the test & result.
1.Disconnected power & pull the Power SW pins apart from the pins, with all basic peripherals connected, then connected power, and shorted the pins. The PC started. Ran for 16 minutes. Then shorted the pins & the PC shut down.
2.18 minutes later, connected the Power SW wires with their pins, tapped on the on/off switch, the PC started again.
3.22 minutes later, shut the PC down by Windows.
4.26 minutes later, tapped on the on/off switch, it won't start, a few more taps, the PC started.
5.Ran for 56 minutes, then shut the PC down by Windows.
6.27 minutes later, tapped on the on/off switch, it won't start, no matter how many times tapping the switch, just won't start.
7.Tried to short the Power SW pins, no power on the pins. Tried 3 more times in 2 hours, simply no power on the pins.

This seems to be how the PC behaves.
1.It starts after all basic peripherals disconnected.
2.It starts only a few times, 5 times the most.
3.If it starts, it can be started by shorting the Power SW pins or tapping on the on/off switch.
4.It doesn't matter whether the basic peripheral are connected or disconnected if it starts.
5.If it starts, it starts by one tap on the on/off switch for the first and maybe the second time starting the PC, then it requires more and more taps on the on/off switch to make a start. After the PC has started 4 or 5 times, it won't start no matter how many times tapping on the switch.
6.If on/off switch can start the PC, Power SW pins have power and the PC can be started by shorting the pins. If on/off switch cannot start the PC, the is no power on Power SW pins.
 
Hello, Mr. rhkcommander959.
Are you still there?
Some new findings. I replaced the original PSU with a Corsair 650X. Switch power on & tapped on on/off switch, no response. Tapped 10 to 15 times, CPU fan runs for a second, then slows down & stopped running. Only the CPU fan, nothing else, even the LED front panel lights did not respond at all, not even a blink. This happened three times in 10 minutes, power off and then on and tap on the on/off switch, gave it 10 to 20 taps, the CPU fan ran for a second.
What does this mean, PLEASE?
Thank you.
 
My best guess is the motherboard is failing, all of your diagnosis has reinforced that idea for me, especially trying a second good power supply. Most likely the south bridge is dying.

You could potentially skirt the issue for a while by jumping pin 16, the only green wire on the 24 pin connector, to a ground pin, while it is plugged in. This might be enough to keep you going for some time. This is essentially what the south bridge does. I usually use a safety pin, I take my pliers and cut the retaining cap off and the spring loaded nature makes it work well for poking either the female end of the connector or through from the back. You can get splice terminals (see pic below) and rig up a possibly short term solution until the motherboard fully dies, with some wire and a button. I would back up any irreplaceable important data before playing with this system further. I haven't tried this 24-pin jumper on a live system in a very long time, but when testing a power supply you need a latching/toggle button. But when tricking the system to run it should take a momentary button so you could repurpose the power or reset button for this override, unless memory fails me, and unless the board is in VERY bad shape. The green wire to ground sends a signal to the PSU to turn on, but there is another wire that says powers' OK.

Socket 775 is very old now so you could do a system upgrade or find a replacement motherboard. You will want to verify if the motherboard installed follows the ATX standard mounting design or if it has an unconventional OEM board, if it's the latter you would need another case too or search ebay for an exact replacement. You could take a picture of the motherboard if you aren't sure what you're looking at.
 

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My best guess is the motherboard is failing, all of your diagnosis has reinforced that idea for me, especially trying a second good power supply. Most likely the south bridge is dying.

You could potentially skirt the issue for a while by jumping pin 16, the only green wire on the 24 pin connector, to a ground pin, while it is plugged in. This might be enough to keep you going for some time. This is essentially what the south bridge does. I usually use a safety pin, I take my pliers and cut the retaining cap off and the spring loaded nature makes it work well for poking either the female end of the connector or through from the back. You can get splice terminals (see pic below) and rig up a possibly short term solution until the motherboard fully dies, with some wire and a button. I would back up any irreplaceable important data before playing with this system further. I haven't tried this 24-pin jumper on a live system in a very long time, but when testing a power supply you need a latching/toggle button. But when tricking the system to run it should take a momentary button so you could repurpose the power or reset button for this override, unless memory fails me, and unless the board is in VERY bad shape. The green wire to ground sends a signal to the PSU to turn on, but there is another wire that says powers' OK.

Socket 775 is very old now so you could do a system upgrade or find a replacement motherboard. You will want to verify if the motherboard installed follows the ATX standard mounting design or if it has an unconventional OEM board, if it's the latter you would need another case too or search ebay for an exact replacement. You could take a picture of the motherboard if you aren't sure what you're looking at.

Found a G45T AM2 V:1.0 board. It started the PC if HDD was not connected. It would not start if HDD was connected to any one of the 4 connectors on the PSU wires. The seller of the board said the board could start the machine & install OS. I connected the HDD to DVD connector & yes, the machine started & ran normally for 5 hours. Then, I connected the HDD back to one of the 4 connectors, the 2nd one from the PSU, and tapped on the start switch, a "pa" burst and smell and the HDD was burnt. Had another HDD connected & tried to reinstall OS. Windows installer found no HDD. HDD info disappeared from BIOS.

Now my new question is: How to get HDD back into BIOS?

Thank you.
 
Hello, Mr. rhkcommander959.
Are you still there?
Some new findings. I replaced the original PSU with a Corsair 650X. Switch power on & tapped on on/off switch, no response. Tapped 10 to 15 times, CPU fan runs for a second, then slows down & stopped running. Only the CPU fan, nothing else, even the LED front panel lights did not respond at all, not even a blink. This happened three times in 10 minutes, power off and then on and tap on the on/off switch, gave it 10 to 20 taps, the CPU fan ran for a second.
What does this mean, PLEASE?
Thank you.
Probably a bad motherboard.

Have you tried unplugging the wiring harness to the power switch from the motherboard, and using a screwdriver or something to bridge the pins, mimicking a known-good switch?
 
Found a G45T AM2 V:1.0 board. It started the PC if HDD was not connected. It would not start if HDD was connected to any one of the 4 connectors on the PSU wires. The seller of the board said the board could start the machine & install OS. I connected the HDD to DVD connector & yes, the machine started & ran normally for 5 hours. Then, I connected the HDD back to one of the 4 connectors, the 2nd one from the PSU, and tapped on the start switch, a "pa" burst and smell and the HDD was burnt. Had another HDD connected & tried to reinstall OS. Windows installer found no HDD. HDD info disappeared from BIOS.

Now my new question is: How to get HDD back into BIOS?

Thank you.

If the drive burned, and another drive after it doesn't get detected, it probably damaged the SATA controller on the motherboard.
 
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