PC is breadboarded, still stuck in a constant on/off power loop.

[coelacanth_]

So this morning after turning on my PC after a night of perfectly fine gaming, I was met by my PC repeatedly turning on and off. This is my 3rd time having this problem and I solved them the last two times, but I'm genuinely stumped this time.

 

So basically what's going on now is that I've met my wit's end and finally breadboarded my motherboard. The only things connected to it are the mobo/CPU power cables, CPU and the cooler, and one stick of RAM. I flip on the power switch on the PSU and my motherboard immediately tries to power on, turns off, and goes into the power loop. This is my first build so I'm not sure which part is at fault here.

 

I'm also very confused as to why my motherboard tries to immediately turn on when I flip the PSU switch while it's breadboarded. My understanding is that you're supposed to short the on/off power switch header with a screwdriver. 

 

Here are my specs:

CPU: Intel Core i5-10400 2.9 GHz 6-Core Processor

CPU Cooler: be quiet! Pure Rock Slim 35.14 CFM CPU Cooler

Motherboard: Gigabyte B460M DS3H Micro ATX LGA1200 Motherboard

Memory: ADATA XPG Z1 16 GB (2 x 8 GB) DDR4-3000 CL16 Memory

Storage: Team CX2 1 TB 2.5" Solid State Drive

Video card: PowerColor RED DEVIL Radeon RX 580 DirectX 12 AXRX 580 8GBD5-3DH/OC 8GB 256-Bit GDDR5 PCI Express 3.0 CrossFireX Support ATX Video Card

Case: Phanteks Eclipse P300A Mesh ATX Mid Tower Case

Power supply: EVGA B5 550 W 80+ Bronze Certified Fully Modular ATX Power Supply

[Sky7734]

That is very strange that the computer immediately turns on. That might mean there's a short somewhere on the motherboard. I would try to troubleshoot that issue first, but considering that this has happened 2 other times, you might just have a busted motherboard.

[mariushm]

There are BIOS options which allow a computer to turn on as soon as stand-by power is received. My motherboard has a  "Turn on pc after power loss" and other such options.

 

First things first, remove power from motherboard and disconnect the battery for at least 5-10 seconds, then put battery back in. This resets the bios settings. You can try to cmos reset button or jumper (if any) but removing battery is guaranteed to do the job. The motherboard needs to NOT receive power from psu otherwise it will power the bios settings from psu instead of battery, so you must disconnect the psu (remove cables ideally, or unplug psu and wait at least 20-30s for the big capacitors in the psu to discharge otherwise even unplugged psu could still provide 5v standby power for a few seconds)

 

If possible, try to turn on the PC with another power supply.

The chipset (which reads the bios and runs everything before the operating system loads) is powered from 5v stand-by from the power supply which is a separate power supply from the ATX power supply, think of it like a small cell phone charger that outputs 5v up to 1-3A 24/7 even when the PC is shut down.

It's possible (rarely) that the 5v standby circuit has degraded to the point where it's still operating fine while the PC is shut down and the chipset only consumes a few mA but as soon as it tries to initialize things the power consumption could jump up to 100+ mA which could cause the standby circuit to become unstable and force the chipset to reset the PC, and therefore you end up in a loop.

 

Try attaching some speaker to the speaker pins (headphones will also work) to see if there's some beeps before the reboot.

 

Use only 1 stick of ram, just the cpu and cooler ... plug just the 24pin and 8 pin ... try to start the system... in a speaker you should get 3 beeps or something like that (see if motherboard has some debug leds, i'm too lazy to look up pictures of that board) which tell you there's no video card present.

 

 

[coelacanth_]

22 minutes ago, Sky7734 said:

That is very strange that the computer immediately turns on. That might mean there's a short somewhere on the motherboard. I would try to troubleshoot that issue first, but considering that this has happened 2 other times, you might just have a busted motherboard.

How would you recommend I try and troubleshoot this? Also this build is less than a week old so I don't know if the mobo would give out that quickly.

[Sky7734]

25 minutes ago, coelacanth_ said:

How would you recommend I try and troubleshoot this? Also this build is less than a week old so I don't know if the mobo would give out that quickly.

Just inspect the motherboard for any noticeable damage, or any broken components on it.

[coelacanth_]

6 minutes ago, Sky7734 said:

Just inspect the motherboard for any noticeable damage, or any broken components on it.

I don't see anything broken on it, though I am only a beginner builder so I'm not sure exactly what I'm looking for.

 

I don't know if it's worth mentioning, but this problem only started happening after I shut off my PC for the night. It was 100% functional with no symptoms before I turned it off.

[coelacanth_]

45 minutes ago, mariushm said:

There are BIOS options which allow a computer to turn on as soon as stand-by power is received. My motherboard has a  "Turn on pc after power loss" and other such options.

 

First things first, remove power from motherboard and disconnect the battery for at least 5-10 seconds, then put battery back in. This resets the bios settings. You can try to cmos reset button or jumper (if any) but removing battery is guaranteed to do the job. The motherboard needs to NOT receive power from psu otherwise it will power the bios settings from psu instead of battery, so you must disconnect the psu (remove cables ideally, or unplug psu and wait at least 20-30s for the big capacitors in the psu to discharge otherwise even unplugged psu could still provide 5v standby power for a few seconds)

 

If possible, try to turn on the PC with another power supply.

The chipset (which reads the bios and runs everything before the operating system loads) is powered from 5v stand-by from the power supply which is a separate power supply from the ATX power supply, think of it like a small cell phone charger that outputs 5v up to 1-3A 24/7 even when the PC is shut down.

It's possible (rarely) that the 5v standby circuit has degraded to the point where it's still operating fine while the PC is shut down and the chipset only consumes a few mA but as soon as it tries to initialize things the power consumption could jump up to 100+ mA which could cause the standby circuit to become unstable and force the chipset to reset the PC, and therefore you end up in a loop.

 

Try attaching some speaker to the speaker pins (headphones will also work) to see if there's some beeps before the reboot.

 

Use only 1 stick of ram, just the cpu and cooler ... plug just the 24pin and 8 pin ... try to start the system... in a speaker you should get 3 beeps or something like that (see if motherboard has some debug leds, i'm too lazy to look up pictures of that board) which tell you there's no video card present.

 

 

I've tried all of that except for using another PSU (don't have access to one) and examining diagnostic leds/beeps (mobo doesn't have any according to my manual). Also I should note that this build is only a week old so I'm not sure if any part has already degraded that quickly.

[Sky7734]

17 minutes ago, coelacanth_ said:

I don't see anything broken on it, though I am only a beginner builder so I'm not sure exactly what I'm looking for.

 

I don't know if it's worth mentioning, but this problem only started happening after I shut off my PC for the night. It was 100% functional with no symptoms before I turned it off.

If this build is only a week old you should still be able to RMA it, but only use that as a last resort. I only really understand visible hardware problems with electronics, not software or non-visible problems, so you'd be better off listening to someone else.