Question Power Switch Won't Work After CMOS Reset (and other issues)

[jaco1994]

Hi everyone! I'm turning to the pros for some help. Sorry for the long post, but this is part of an ongoing issue and I'm really stuck. I can't find anything helpful through searches.

TLDR: The PC will not power on. MB has power (logo LEDs light up), but no power is getting to switch. No fans spin. No response when pressing power or reset buttons, shorting across power jumper, etc.

Current Build

• MB: ASUS TUF Z390-Pro Gaming
• CPU: Intel Core i5-9600K
• RAM: CORSAIR VENGEANCE LED 16GB
• PSU: CORSAIR TX-M Series TX550M
• GPU: ASUS Dual GeForce GTX 1660 Ti

Quick history
Initial build: March 5, 2019 - all brand new parts

During initial boot (after build), the PC was stuck in a boot loop. After diagnostics and BIOS update, PC started working fine. After a few weeks, the PC was stuck in a different type of boot loop. PC would attempt to turn on, 0.5-1 sec later the PC would shut down, restart, 0.5 sec-1 sec later PC would shut down, restart, etc. This time, it wouldn't even try to post and BIOS update didn't work. Returned MB, RAM, and CPU. Replaced MB with ASUS TUF Z390-Pro, replaced RAM with CORSAIR TX-M Series TX550M, and ordered new i5-9600K.

After rebuild with new MB and CPU, PC worked fine for a few weeks, then was stuck in similar boot loop. PC would attempt to turn on, 0.5-1 sec later the PC would shut down, restart, etc. This time RMA'd MB and PSU. ASUS "repaired" skewed pin on MB and Corsair sent a new PSU. Reassembled PC and it powered on fine.

I've been using the PC for less than 1 week and it started the boot loop again today. PC would attempt to turn on, 0.5-1 sec later the PC would shut down, restart, etc. I tried reseating RAM, GPU, checked plugs, etc. but nothing seemed to correct the issue. I unplugged the power cord and pulled the CMOS battery, let it sit for a few minutes, reinstalled the CMOS battery, plugged in the power cord, flipped the switch and saw the MB LED logo light up, pressed the power button, and nothing happened. PC didn't try to power on. NOTHING. So, this is a new problem and I'm out of ideas on how to fix it.

I checked and rechecked plugs, etc.

• 24-pin connector is good
• 8-pin connector is good
• Fans are all plugged in
• RAM is seated and secure
• GPU is seated and secure
• CMOS battery is seated and secure

Notes

• MB is receiving power because the TUF logo lights up.
• I am down to bare bones now, so GPU and peripheral failure won't be a factor.

Other Troubleshooting

• Paperclip test for TX550M - fan spins so not likely a bad PSU
• Tried a spare, working PSU - no power on
• Tried shorting across the power jumper - no power on
• Tried resetting CMOS by pulling battery again and shorting RTC jumper - no power on

I called ASUS and their "Advanced Troubleshooting Team" is going to call me back sometime within the next 24 hours. I'm not holding my breath.

Current Issue
The PC will not power on. MB has power (logo LEDs light up), but no power is getting to switch. No fans spin. No response when pressing power or reset buttons, shorting across power jumper, etc.

I have no idea what to try next. Any other ideas out there?

 

[jaco1994]

Anyone out there have any idea what I can try with this system? I RMA'd the MB and CPU. I'm also replacing the battery backup. Any way the m.2 could be causing a problem? I feel like the system would still boot even if the m.2 was defective.

 

[cherry blossoms]

Take your battery backup out of the system power loop and try powering the system directly from the wall.

Try other outlets to make sure it's not an issue with the outlet.

Taking the system down to pure barebones is a good idea. Do you bootloop with everything disconnected (including all drives). Does the system consistently correctly POST ?

Disconnect reset switch, other case leads in case of short/sticking reset switch or other short.

All standoffs correctly placed?

Computer speaker connected? Any beep codes?

 

[jaco1994]

Take your battery backup out of the system power loop and try powering the system directly from the wall.

Try other outlets to make sure it's not an issue with the outlet.

Taking the system down to pure barebones is a good idea. Do you bootloop with everything disconnected (including all drives). Does the system consistently correctly POST ?

Disconnect reset switch, other case leads in case of short/sticking reset switch or other short.

All standoffs correctly placed?

Computer speaker connected? Any beep codes?

Thanks for the ideas cherry blossoms.

I removed the UPS and plugged straight into a working outlet and tried other outlets. Didn't have an impact.

The system would boot loop with all drives installed and bare bones. Didn't seem to matter. I also tried different configurations (one drive connected, then different drive connected the next time, no drives connected, etc.).

The system would consistently and correctly POST until this issue.

Disconnected case leads/switches and tried to start by shorting power jumper.

Standoffs are good. No extras touching board.

Speaker connected. No beeps.

-------------------------------------------------
I even thought maybe Windows putting the PC to sleep was causing the problem, so I shut down the system nightly.

The ONLY thing I noticed is that, on occasion, I would press the power button, the unit would try to power up, shut down after a second or two, then start up normally. It would POST with no issues and load Windows. It definitely exhibited this behavior any time I adjusted the hardware configuration, so I just thought it was normal for the MB to do this. No other PC I've built does this though.

I also noticed the night before the boot loop started, when I shut the system down, it sounded like it shut down "hard." I don't know how else to explain it, but when it shut down and powered off, it was a louder power off than normal and the "click" made me think something may have just happened. Sure enough, it was stuck in a boot loop the next morning. It didn't sound like a short or anything (e.g. no buzzing sound). Just a kind of thud when it powered off.

 

[cherry blossoms]

In theory, a UPS shouldn't damage your system. In practice, if it was a poor quality or old UPS, could contribute. If you have another PSU you can test with, test your system with it , WITHOUT the UPS

By barebones, you also pulled the video card and are running on internal graphics?
Anything connected to the RGB headers? Disconnect
Do a CMOS reset. Page 1-10 of the manual
Possible need to disable your MemOK switch (or re-enable if off)? The procedure to clear the task and disable is in your manual page 1-9
Test with only 1 DIMM in the system.

Any consistency to the troubleshooting LED's where the system fails?