Question No boot, and yellow light stays on ?

Alan Alan

Great
Aug 9, 2022
200
9
95
2
Motherboard: ASUS Prime Z370-A LGA 1151 (300 Series)

Well, I shut the computer down as usual and turned of the power supply switch. Next time I turned it on it won't boot and the yellow light stays lit. Not sure what to think except the ram has a problem. The owners manual is terrible and doesn't explain what the lights are for. It talks about beeps during boot but there is no beeper. As far as I can tell the yellow light is for ram as some general industry color. I'm curious if the bios battery is borderline low as it's 4 years old. I rarely throw the power supply switch. It was off 16 hours then poof, no boot. Have there been issues with ram after a complete shut down ?

I think there's a ram test button on the board, it causing the yellow light to flash. I wish they'd write manuals like they should. Any help appreciated, and tia.
 

Lutfij

Titan
Moderator
When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list them like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model.

The owners manual is terrible and doesn't explain what the lights are for.
https://dlcdnets.asus.com/pub/ASUS/mb/LGA1151/PRIME_Z370-A/E13271_PRIME_Z370-A_UM_WEB.pdf
Page 1-13, section 1.1.8: Onboard LEDs.

It talks about beeps during boot but there is no beeper.
You need to add a POST speaker located just above the front panel connectors on the motherboard in order get beep codes.

As far as I can tell the yellow light is for ram as some general industry color.
You sure you're not looking at the Standby Power LED?
 

Alan Alan

Great
Aug 9, 2022
200
9
95
2
Well thanks for that, beforehand the system started with the cpu or red indicator, then moves up the ladder to the mem test or yellow then the white vga and ends when booted or yellow green. Now the yellow light remains on and after pressing the mem test button it does start flashing. It's suppose to be calibrating the memory and finish booting. I'm assuming if it continues to flash the mem light then something is wrong. I have 4 separate memory modules so I'm thinking of pulling all 4 testing them one at a time. I did work the machine pretty hard this week and it may have something to do with it. I can't think of another way other than individual testing each module right now. I'm hoping one of them will keep the yellow light on and that will be the problem child. Do you think re seating them first is worth a try. It's a bit humid sometimes and being four years old re-seating them may clean the contacts. I also have some deoxit D5 contact cleaner. Maybe I could scrub the contacts with a q tip saturated with D5 and prevent static in the process. Any suggestions?
 

Alan Alan

Great
Aug 9, 2022
200
9
95
2
When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list them like so:
CPU:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model.

The owners manual is terrible and doesn't explain what the lights are for.
https://dlcdnets.asus.com/pub/ASUS/mb/LGA1151/PRIME_Z370-A/E13271_PRIME_Z370-A_UM_WEB.pdf
Page 1-13, section 1.1.8: Onboard LEDs.

It talks about beeps during boot but there is no beeper.
You need to add a POST speaker located just above the front panel connectors on the motherboard in order get beep codes.

As far as I can tell the yellow light is for ram as some general industry color.
You sure you're not looking at the Standby Power LED?
Well, I think the mobo is blown, I took out all of the peripherals leaving nothing but the video connected. Pulled all 4 memory modules out and tried them one at a time in the slot for only 1 module. Pulled the bios battery for a few hours while taking a break and tried the memory button that flashes slow the faster then stays yellow. It doesn't turn off and the next step is the boot. Usually the red comes on first saying the cpu is ok followed by the yellow memory led then the final boot light. I think it was green but it never gets that far. I was playing a memory intensive video game for about 8 hours and started having to wait which was unusual then the game started back up. I'm assuming the game was having trouble writing or reading to main memory when it gave me the waiting for game error. At this point I don't know what to do. Send the mobo to asus for repair or upgrade to the x299 mobo and get a new processor. I can fix low level electronics as I was a tech for 40 years but I need a schematic. It's possible the voltage regulator blew the supplies power to the memory. If anyone knows how to get schematics please let me know. I have an ASUS Prime Z370-A LGA 1151 (300 Series) Intel Z370 HDMI SATA 6Gb/s USB 3.1 ATX Intel Motherboard The processor is Intel Core i7 8th Gen - Core i7-8700K Coffee Lake 6-Core 3.7 GHz (4.7 GHz Turbo) LGA 1151 (300 Series) 95W ... The memory is CORSAIR Vengeance LPX 16GB (4 x 4GB) DDR4 3000 (PC4 24000) Memory Kit Model CMK16GX4M4B3000C15 The water cooler is Corsair Hydro Series, H150i PRO RGB, 360mm. 3 X 120mm ML PWM Fans, Advanced RGB Lighting & Fan Control w/ Software. ... The power supply is EVGA SuperNOVA 750 G3, 220-G3-0750-X1, 80+ GOLD, 750W Fully Modular, EVGA ECO Mode with New HDB Fan, Includes FREE Power ... and the hard drive is Kingston KC1000 M.2 2280 480GB NVMe PCIe Gen 3.0 x4 Lanes MLC Internal Solid State Drive (SSD) SKC1000/480G There are several other nvme drives in a riser card and on the mobo and 4 sata drives that striped raid 0. What a pain when this happens. As far as I know a protection fuse opened to the memory regulator. Has anyone shipped a mobo to asus for repair?
 

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