Computer Building Problems

By aidanjohnb ·
Tags: Hardware
Hello, everybody, I am in the process of building a PC for my friend and it is all assembled and I turn on the power supply and the motherboard turns on then off repeatedly. The power LED turns on then off the on and keeps doing that until I shut it off. Sometimes if it is shut off long enough and I turn the power supply on and the motherboard lights will come on for a second then turn back off. I have verified that all of the cables are connected and are not loose and still no luck. Any help is appreciated.

ASUS Z370 Prime-A

Intel Core i7-8700k


16GB of Corsair Vengeance RAM


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Start with the obvious

by OH Smeg Moderator In reply to Computer Building Problem ...

Remove the M'Board from the case and place it on some white paper.

Then reduce it to the mininum that it will run with so the CPU 1 RAM Module and plug in the PS.

A set of fly switches is useful but you can turn it on by shorting out the pins with a screwdriver if necessary for the Off/On switch and see if it keeps running now.

If it does continue adding one piece at a time but first making sure that you power down and remove the Power Lead from the Power Supply before adding any hardware.

If it doesn't work remove the CPU and make sure it is in the correct way which can cause this to happen as well and the most obvious check the Power Supply it may not be working properly.

While not common I have seen several that don't work new out of the box and all that it means with a LED turning on and off is that there is 1.5 Volts present and in no way implies that any of the other voltages are right or that there is any current present.

If the unit works out of the case look at the mounting points and make sure that there is not one not lined up with a mounting Hole in the M'Board as this will cause a short circuit.

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Computer powers on and then turns off

by allenjame1991 In reply to Computer Building Problem ...

Loose cable
If the problem persists, make sure all cables inside the computer case are firmly attached to the motherboard and each component. You'll want to check the IDE cables and SATA cables, which are typically connected to the hard drive, CD or DVD drive, and floppy drive (if present). Check both ends of each cable and make sure they are firmly attached to the component and the motherboard. Turn on the computer and test to see if this resolves the issue.

Tip: Sometimes the best way to verify a cable is not loose is to disconnect and then reconnect the cable on both ends.

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Electrical short
An electrical short in a computer, which may cause power issues, happens when pieces of metal cause a path for electricity to flow through that shouldn't exist. Computers are full of screws, as they hold nearly ever internal component in place, and from time to time they can come loose. Lift up your computer and gently rotate it while softly shaking it from side to side. If you here what sounds like small rocks banging around, it's likely that you have loose screws inside the case. Open the computer up and remove them.

Memory issue
Verify the memory modules are properly seated in the memory slots on the motherboard. To do this, open the computer, remove the memory modules from their slots, and gently reseat them. It also is important to note that memory modules should be installed in pairs and in matching slots, which are designated by matching colors. Make sure the chips are firmly seated and the clamps on both sides of each chip snap into place. Plug in the power cord and turn the computer on to see if the issue is resolved.

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