[SOLVED] Why does my PC go into power on/off loop?

[monsieurderriere]

Problem
PC does not boot into OS, keeps looping by powering on and off.
BIOS reports only half of installed memory available.

Specs

• MB: MSI B450 Gaming Pro Carbon AC ATX AM4 (click here to download manual)
• CPU: Ryzen 7 2700X 3.7 GHz 8-Core
• GPU: Asus GeForce RTX 2080 8 GB ROG Strix Gaming OC
• RAM: G.Skill Trident Z 2 x 8 GB DDR4-3200 CL14
• SSD: Samsung 970 Pro 512 GB M.2-2280 SSD
• PSU: Corsair RMx 650 W 80+ Gold Fully-Modular ATX
• OS: Windows 10 (1909)

What happened?
This is the first issue ever with my PC after 1 year of mid-heavy use.
Trying to remember as best as I can:

• Played a graphics intensive video game.
• It froze, so I tried Ctrl+Shift+Esc and Ctrl+Alt+Delete
• No results, so I pressed the physical reset button
• Computer went into loop: turned off, turned on, turned off, turned on...
• Switched the PSU from I (on) to O (off), cutting power completely
• Turned the computer back on, has same looping as before, cut power completely once more
• Reset the CMOS by shorting JBAT1 on my MB (see manual)
• While I was at it, I also used compressed air to clean some dust
• MB reported that CMOS was reset, so I agreed and went to BIOS settings
• The only abnormal thing I see is that instead of 16 GB of RAM, the screen reports that I only have 8 GB, even though both sticks are recognized
• Trying to boot to OS results in loop as described before

What did I already try to investigate?

• Pulled open the PC and:
  • removed GPU
  • removed both RAM sticks
  • disconnected all power and data cables except for front panel (JFP1), CPU power (CPU_PWR1, CPU_PWR2, CPU_FAN1) and main power (ATX_PWR1)
• With only MB, CPU, and one fan connected to power, I turn on the power using the I/O switch of the PSU
• I notice that the Flash BIOS red light blinks 3 times (manual page 28, top left corner)
  • It keeps doing this every time I re-supply power to the MB
• I press the power button, fan starts to spin.
  EZ Debug light (see manual page 42) blinks on CPU and then stops on DRAM: OK!, because RAM is not installed
  • Some confidence that MB, CPU and PSU are fine
• Installed the 1st RAM stick to all DIMM slots one-by-one: turned power off, installed stick to new slot, turned power on.
  EZ Debug light blinks past CPU and DRAM and stops on VGA: OK!, because GPU is not installed
  • Some confidence that the 1st RAM stick is fine
• Did the same for 2nd RAM stick to all DIMM slots one-by-one.
  EZ Debug light always stops on DRAM: BAD?!

EDIT: To be clear, these are the tests that I did:

• Stick 1, DIMMA1 - EZ Debug stays on "VGA": seems OK
• Stick 1, DIMMA2 - EZ Debug stays on "VGA": seems OK
• Stick 1, DIMMB1 - EZ Debug stays on "VGA": seems OK
• Stick 1, DIMMB2 - EZ Debug stays on "VGA": seems OK
• Stick 2, DIMMA1 - EZ Debug stays on "DRAM": NOT OK
• Stick 2, DIMMA2 - EZ Debug stays on "DRAM": NOT OK
• Stick 2, DIMMB1 - EZ Debug stays on "DRAM": NOT OK
• Stick 2, DIMMB2 - EZ Debug stays on "DRAM": NOT OK

Stopped investigating further on my own.

Questions

• What could have happened?
  • Is pressing the reset button, resetting CMOS or using compressed air to blame in any way?
  • Could one of the RAM sticks be done for? Or is it possible that there is something wrong with the MB?
• Why does the Flash BIOS red light blink 3 times every time I switch the power on?
• What more can I do to troubleshoot this issue and get my PC working again?

 

[Ketchup79]

Good troubleshooting. As you noticed, DRAM slot 2 is bad. Can I assume you checked slots 3 and 4?

As for the cause, a power surge or a chop power supply can cause something like that, which don't seem to be the case here, so it sounds like nothing more than board malfunction. Is it still under warranty?

As far as getting Windows back up here and now, leave slot 2 empty and see if Windows will repair when you select that option. Depending on what was damaged, you may have to do a full OS reinstall.

 

[monsieurderriere]

Hi. Thanks for the swift reply.

Good troubleshooting. As you noticed, DRAM slot 2 is bad. Can I assume you checked slots 3 and 4?

I tried all slots (DIMMA1, DIMMA2, DIMMB1, DIMMB2, see manual in OP) with both RAM sticks, one stick at a time, so 8 experiments in total. For the first stick, EZ Debug gave me no errors. For the second stick, EZ Debug always stopped on DRAM (notifying about error):

• Stick 1, DIMMA1 - EZ Debug stays on VGA: OK
• Stick 1, DIMMA2 - EZ Debug stays on VGA: OK
• Stick 1, DIMMB1 - EZ Debug stays on VGA: OK
• Stick 1, DIMMB2 - EZ Debug stays on VGA: OK
• Stick 2, DIMMA1 - EZ Debug stays on DRAM: NOT OK
• Stick 2, DIMMA2 - EZ Debug stays on DRAM: NOT OK
• Stick 2, DIMMB1 - EZ Debug stays on DRAM: NOT OK
• Stick 2, DIMMB2 - EZ Debug stays on DRAM: NOT OK

As for the cause, a power surge or a chop power supply can cause something like that, which don't seem to be the case here, so it sounds like nothing more than board malfunction. Is it still under warranty?

How can we know for sure whether or not this was a power surge problem?

MSI Standard Warranty seems to be 3 years since manufacturing. My manufacturing date is January 2019, so yes, my motherboard seems to be under warranty.

As far as getting Windows back up here and now, leave slot 2 empty and see if Windows will repair when you select that option. Depending on what was damaged, you may have to do a full OS reinstall.

I will try booting up with only one memory stick.

Thank you.

 

[Ketchup79]

Good news about the warranty. Get with MSI and see what is needed to get the RMA process started.

 

[monsieurderriere]

@Ketchup79 I managed to boot to the OS using only one memory stick. This memory stick will run in any DIMM slot, so for me it seems like it is not a motherboard issue. Do you still think it is a motherboard issue or could it be that one of the memory sticks is faulty instead?

 

[Ketchup79]

Good to know. Nah, sounds more like that stick of RAM. Which is great because it's so much easier to replace and has a lifetime warranty.

 

[monsieurderriere]

@Ketchup79 Thanks for the help! I have contacted G.Skill and am waiting for response now. Will post back with the results.