Question PC won't POST after PSU change?

K4long

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Feb 11, 2014
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Heya~

After days of troubleshooting and none appears to work, I'm requesting help here to find what can be the cause of this issue.

PC Specs:
  • CPU : Ryzen R5 3600
  • MB : Asrock AB350 ITX Fatality
  • GPU : RTX 2080 (not super)
  • RAM : Kingston HyperX PREDATOR 16GB DDR4-3200 CL16
  • Old PSU : CM v650 Gold
  • New PSU : Corsair SF750 Platinum
Symptoms:
  • After installing the new PSU, it will cycle at least 3 times before it Post.
  • After pressing the power button, Fan turns a bit, GPU goes full fan (the AMD expected behavior), RAM LED light is on. Then, it is off and starts another cycle.
  • When it is able to, the machine starts and can be used properly.
  • Restarting through windows, sometimes it will not post even though the power is delivered (All fans are spinning, RAM LED is on). It requires a press of the restart button to have it start properly.
  • After this, power down the system and turn in on again appears to boot without any issue. But, leaving it off for a while as I sleep, the problem will happen again the next day.
Troubleshooting attempt:
  • SF750 give me 2 CPU cable, change that and change the port in the PSU. Didn't help.
  • Change the fan profile from Full Speed to anything in the bios. Didn't help.
  • Pull out the power plug and hold the power button for 5 seconds. Didn't help
  • Refitting all the cables (ATX, CPU, PCie, Sata). Didn't help
  • The SF750 is not the product unit that is within the recall
From the above, what's left is to test changing back to the Old PSU but it is such a hassle where this New PSU is pretty much superior that should not cause any issue, can't find many articles where people RMA this as well. Also, it doesn't make sense where things work perfectly with inferior PSU before. Then, to test the PSU in some other machine, sadly, I don't have any PC friends close to me.

In a way, it is just an inconvenience where my boot time will take longer but I would not know what is the effect to the components in long run. My suspicion is the compatibility, AB350 is not exactly a new board, it is one of the board that comes with Gen1. Or, knowing how small that PSU is, it might take a longer time to be ready compared to that ATX v650 PSU, but I'm not an electrical engineering expert so who knows.

Any help will be appreciated!
Cheers!
 

K4long

Honorable
Feb 11, 2014
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10,510
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Are you running the new PSU with the Hybrid Switch turned on or off? Does that make any difference? Setting it to the off position turns off semi-fanless mode.
I don't think this PSU has it. Checked in the manual and can't find it. Unless I miss it
- https://www.corsair.com/us/en/Categories/Products/Power-Supply-Units/Power-Supply-Units-Advanced/SF-Series/p/CP-9020186-NA

From the pics, I can't find any visible button beside the main power. Or, is there any special way to turn it off?
 
I don't think this PSU has it. Checked in the manual and can't find it. Unless I miss it
- https://www.corsair.com/us/en/Categories/Products/Power-Supply-Units/Power-Supply-Units-Advanced/SF-Series/p/CP-9020186-NA

From the pics, I can't find any visible button beside the main power. Or, is there any special way to turn it off?
My mistake, i got your old and new PSU's mixed up. The Hybrid Switch is on your old PSU.

I can't see any reason your new PSU should not work perfectly well with your PC. I think your suspicion the problem is connected to the compatibility with your motherboard is the most likely answer. Is your motherboard updated to all the latest drivers and BIOS version 6.60 ?
The problem could also be connected to one of the setting in the BIOS. Have you tried enabling/disabling your motherboards "Cool 'n' Quiet" feature? You could also try enabling/disabling the "Restore on AC/Power Loss" option.
 

K4long

Honorable
Feb 11, 2014
5
0
10,510
0
My mistake, i got your old and new PSU's mixed up. The Hybrid Switch is on your old PSU.

I can't see any reason your new PSU should not work perfectly well with your PC. I think your suspicion the problem is connected to the compatibility with your motherboard is the most likely answer. Is your motherboard updated to all the latest drivers and BIOS version 6.60 ?
The problem could also be connected to one of the setting in the BIOS. Have you tried enabling/disabling your motherboards "Cool 'n' Quiet" feature? You could also try enabling/disabling the "Restore on AC/Power Loss" option.
Sounds like a motherboard issue. Power god signal not synched up with what the PSU is offering. You have the newest BIOS?
Have tried disabling the "Cool 'n' Quite" feature and the issue persist. Not yet tried the "Restore on AC/Power Loss" option and BIOS is not updated to the latest for now. Will try the "restore power" thing option first before the BIOS update. Always nervous doing a BIOS update even though I've done it multiple times.
Thanks for the advice all, might take a while for an update, need to wait for a day on every change (since the issue is only replicable if I turn off the machine for a while).
 

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