So I built a computer the other day, and it is having booting issues. I reassembled it a bit of times and I think its an ESD problem because when I boot it the case fans turn on, and the LED flashes. When I try to force shutting it down, and starting it again it does a different sequence with the cases fans trying to turn on with the LED flashing.

To boot my computer, I take the cord off the PSU and then proceed to holding down the case power button to get rid of the ESD which allows me to boot.

My main concern is if I need to return all my parts due to ESD or just some of them?

I suspect that it's a PSU/MOBO issue, but I am still a student and don't know much better.

EDIT: This is a custom built computer with Windows 10 pro 64bit.

-CPU: Intel Core i5-8400 Coffee Lake 6-Core 2.8 GHz (4.0 GHz Turbo) LGA 1151 (300 Series) 65W BX80684I58400 Desktop Processor Intel UHD Graphics 630

-GPU: MSI GeForce GTX 1060 DirectX 12 GTX 1060 ARMOR 6G OCV1 6GB 192-Bit GDDR5 PCI Express 3.0 x16 HDCP Ready ATX Video Card

-RAM: ADATA XPG Z1 16GB (2 x 8GB) 288-Pin DDR4 SDRAM DDR4 2400 (PC4 19200) Desktop Memory Model AX4U240038G16-DRZ

-MOBO: MSI ATX Motherboard Motherboards Z370-A PRO

-PSU: EVGA 600 B1, 80+ BRONZE 600W, 3 Year Warranty, Includes FREE Power On Self Tester, Power Supply 100-B1-0600-KR

-HDD: Western Digital 1TB 3.5" 7200 RPM SATA III 64MB Cache Desktop Hard Drive (Blue)

  • Modern BIOSes/UEFI are intelligent programs. If a first boot was unsuccessful, they would try different (relaxing) configuration and the sequence might look different, with different delays etc. Some times it takes for BIOS several attempts to boot before a success. If "the LED" are flashing, then there is some serious problem, likely the memory isn't up to reported configuration, and behaves flaky. Jan 23, 2018 at 7:21
  • Also, "ESD" means ElectroStaticDischarge. Is this what you mean? Jan 23, 2018 at 7:25
  • The MoBo manual should describe what the different LED flash sequences mean, allowing an improved guess at what's wrong. Likely: some connector not properly seated, or CPU/fan/socket assembly not properly seated. This can allow instant CPU overheat. Jan 23, 2018 at 10:31
  • Found the manual (OP: Always read the manual before you come here asking for help!) There is more than one LED, apparently: EZ Debug LED These LEDs indicate the status of key components during booting process. When an error is occurred, the corresponding LED stays lit until the problem is solved. CPU - indicates CPU is not detected or fail. DRAM - indicates DRAM is not detected or fail. VGA - indicates GPU is not detected or fail. BOOT - indicates the booting device is not detected or fail.
    – Dampmaskin
    Jan 23, 2018 at 15:40
  • Yeah it seems the problem has been fixed. Thanks guys! Jan 23, 2018 at 21:51

2 Answers 2


First, in my opinion it was proper asking this question at the EE.SE site.

You give no information about which computer you troubleshoot (PC? Notebook? Custom made computer? Based on MCU?), however some words lead to guess that it is a kind of x86/x64 based PC.

To boot my computer, I take the cord off the PSU and then proceed to holding down the case power button to get rid of the ESD which allows me to boot.

This should be a good explanation to start with. When any device power off, there's usually internal (to the device) reset signal which resets it to the default state, and when you power device on again, this device restarts in the "fresh" default condition.

I bet in your case there's something wrong with some reset signal, so that you have to discharge power supply circuitry in order to get the device actually reset.

What can be the cause?

  1. some wiring problem. Check all the wires and connectors, with mains disconnected, disconnect every connector and examine if all contacts from both sides are in, not missing and not bent. Ensure you put connectors properly (there're some header connectors which can be connected in wrong direction - it should not cause fault or fire, but can cause incorrect operation);

  2. internal device fault. Unfortunately you will not be able to find it without specific electronics skills and understanding how your exact computer works, thus I recommend, if you have spares, try them - replace power supply and see the result, use another main board with this power supply. With your description of the issue I would question operation of the PSU standby circuit (in case it is standard ATX PSU).

  3. software issue. May not be applicable to your configuration, but worth mentioning. There were some computers (mostly from previous era of computing), software running on them, if leaving some detectable executable code in the RAM before short power cycle or reset, after this power cycle or reset, due to nature of BIOS operation, execution may erroneously jump to these code remainders and cause misbehave. The only way to eliminate such issues was turn device off for some time to allow everything discharging in the machine and thus causing RAM contents loss. It is very unlikely that it is your case though.

  • Some computers like my Dell 690's have a tamper detect switch. If the case is opened BIOS issues a warning message during boot-up, but I think the OP may have a mobo problem.
    – user857748
    Jan 22, 2018 at 23:48
  • Okay so I updated the description of my problem with the parts list, and I will see if I can do the suggestions made. I also ordered a replacement MOBO and PSU. Jan 23, 2018 at 1:46
  • I voted to migrated the question from the EE.SE because I felt like this was more of a computer troubleshooting question rather than a design problem for electronics, computer hardware, etc., which is something that we take of at the EE.SE.
    – user738756
    Jan 30, 2018 at 0:22

Obviously "ESD" has nothing to do with anything here. To begin, I would advise to clear up CMOS and start with fail-safe defaults. Sometimes BIOS/UEFI store some wrong configuration internally, which can prevent PC from normal booting.

First, disconnect your PSU from AC outlet. Wait. Then remove CR2032 CMOS battery. Then short battery terminals with a piece of wire or tweezers. Hold the short for few seconds to ensure that all elements in the CMOS power rails are discharged. (nowadays a voltage as small as 0.6V might keep information in CMOS memory). Then restore CMOS battery, and try to start your PC. If successfull, you will boot into BIOS/UEFI setup, where you should find a way to set default or fail-safe configuration.

(Some mainboards do have some jumper to clear CMOS, but I prefer explicit power discharge)

  • And then run first the Microsoft Memory Diagnostics, bootable from stand-alone CD. Jan 23, 2018 at 7:30
  • Looks like you were right about the ESD. Thank you. Jan 23, 2018 at 21:52

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