Question Motherboard LED flashes once,fans working but no POST no mouse/keyboard lights

tousif47

Commendable
Dec 3, 2019
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Hi,

So I just assembled my new PC. I noticed when I first connected the PSU power cable from power line and turned on the PSU switch, the LED (just the motherboard LED) flashed just once. Then when I turned on the power switch there was no LED light on the motherboard but all the fans are spinning, RAM LED also lit up. But there was no display no power at mouse/keyboard. I turned off the power line and turned on again, again the motherboard LED flashed once! Again I started the PC, same problem! This time I made a forced shutdown by holding the start button, then restart the PC. No flashing this time but again no display or keyboard mouse power. As before fans were spinning, RAM LED lit but motherboard LED didn't.

I have tried taking out CMOS battery then reinstalling it. I stripped down all the parts, checked for bent CPU pins (looks fine), performed the paperclip test on PSU (it works), lastly I took the motherboard out on a safe spot from any metal or electrically charged stuff, connected the 24pin and turned on the PSU switch. Again the LED flashed once! Note that nothing else was connected, even the CMOS battery is out.

Any suggestions on how to fix this?

My setup is as follows:
CPU: i5 12400
PSU: CX550 80plus bronze
Motherboard: Aorus B660M pro ax
RAM: 3x8 GB DDR4
GPU: GTX 1660
Monitor: Xiaomi Redmi 1A 23.8inch

No extra cooler or anything.

Appreciate the helps, thanks
 
Last edited:

Zerk2012

Titan
Ambassador
connected the 24pin and turned on the PSU switch. Again the LED flashed once! Note that nothing else was connected, even the CMOS battery is out.
Put the battery back in, use one stick of memory, connect the CPU power plug and the 24 pin power plug, CPU and cooler installed. Leave the video card out, connect the monitor to the motherboard and try again.

A paperclip test only says the fan works on the power supply.

Where did you even find a new, old CX500 watt power supply.
 

DSzymborski

Titan
Moderator
Not sure why the CX500 is being used at all here. Mediocre (to be kind) PSUs made a decade ago aren't typically good ideas. The pin test doesn't actually tell if a PSU is working properly or not. I'd certainly replace that and test it again because it should have been replaced under any and all circumstances.
 

tousif47

Commendable
Dec 3, 2019
7
0
1,510
0
Put the battery back in, use one stick of memory, connect the CPU power plug and the 24 pin power plug, CPU and cooler installed. Leave the video card out, connect the monitor to the motherboard and try again.

A paperclip test only says the fan works on the power supply.

Where did you even find a new, old CX500 watt power supply.
Apologies for fat fingers. It's CX550. I didn't buy it brand new but it came from a perfectly running rig and I also tested it with another rig today. PSU is fine IMO.

Just to note the fans and RAM lights are working. It seems to me that the I/O ports at back and mobo lights are not working, while the port on the mobo are working. I cleaned the RAMs and tried with just one (as you suggested), same problem.
 

tousif47

Commendable
Dec 3, 2019
7
0
1,510
0
Not sure why the CX500 is being used at all here. Mediocre (to be kind) PSUs made a decade ago aren't typically good ideas. The pin test doesn't actually tell if a PSU is working properly or not. I'd certainly replace that and test it again because it should have been replaced under any and all circumstances.
Sorry for misunderstanding, it should be CX550 (I fixed it). And I tested the PSU on another rig today, it works fine (it came from a perfectly working machine anyways).
 

Zerk2012

Titan
Ambassador
Apologies for fat fingers. It's CX550. I didn't buy it brand new but it came from a perfectly running rig and I also tested it with another rig today. PSU is fine IMO.

Just to note the fans and RAM lights are working. It seems to me that the I/O ports at back and mobo lights are not working, while the port on the mobo are working. I cleaned the RAMs and tried with just one (as you suggested), same problem.
Did you do all of this?
Put the battery back in, use one stick of memory, connect the CPU power plug and the 24 pin power plug, CPU and cooler installed. Leave the video card out, connect the monitor to the motherboard and try again.
 

tousif47

Commendable
Dec 3, 2019
7
0
1,510
0
Did you do all of this?
Put the battery back in, use one stick of memory, connect the CPU power plug and the 24 pin power plug, CPU and cooler installed. Leave the video card out, connect the monitor to the motherboard and try again.
Yes I did! Is there any way to attach photos or videos? Maybe I can show it directly!
 

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