[SOLVED] Intermittent power on

[Red61]

Sometimes my motherboard won't turn on. I have to keep turning the power off for six or seven times to get it to start. I have reset the bios, taken everything possible of the board, even ram. I have checked the power supply with a psu checker, all lights on the checker work except - 5v. When I turn the mains power on there is a red led light on under a heat sink that comes on. When I press the front power switch on, there is a blue on but the computer doesn't start, if I leave it for about a minute sometimes it just starts up. I am thinking a motherboard fault, but I just don't know.
Asrock AB350 K4 PRO.
https://www.asrock.com/mb/AMD/AB350 Pro4/index.asp#Specification.

 

[curley81]

try a different psu if u can borrow one or have a spare. had same-ish problem twice with x470 MB after power surge, read it could be both PSU or MB. mine turned out to be MB but because yours does start up sometimes im thinking might be PSU, what make and model PSU do you have?
also check for large amounts of dust inside your current PSU

 

[Red61]

try a different psu if u can borrow one or have a spare. had same-ish problem twice with x470 MB after power surge, read it could be both PSU or MB. mine turned out to be MB but because yours does start up sometimes im thinking might be PSU, what make and model PSU do you have?
also check for large amounts of dust inside your current PSU

Psu is an Corsair VX550. I don't know anyone I could borrow one from. I was leaning towards psu but I just don't know, like why dose it check ok with the psu tester.

 

[SM/Madao]

Psu is an Corsair VX550. I don't know anyone I could borrow one from. I was leaning towards psu but I just don't know, like why dose it check ok with the psu tester.

what type or model of PSU Tester is that?
if it merely checking (+12V , -12V , +5V , -5V , +3.3V , +5V Stand by (SB) 12V power Good ( PG ) )
This is not good enough tester, it does not say whole thing and it not necessary mean whole component inside PSU is in good condition. As curley81 say, it better to get spare PSU.

 

[curley81]

Psu is an Corsair VX550. I don't know anyone I could borrow one from. I was leaning towards psu but I just don't know, like why dose it check ok with the psu tester.

because Its much easier to swap a psu to test it and eliminate it as the problem you dont even have to install the new one just test it with your old one still installed and with case open, also whenever you have power problems its the first thing you should look at, and large amounts of dust can cause static inside the psu and cause problems like yours, i have a corsair rm1000x but have a 850w evga as a spare, if its the same with another psu you will know its something worse like MB. and a psu is generally less cost than a MB

sorry i misread your question about the psu tester, thought you were asking why it would be the psu but the statment above is still good, as SM/madao says the only way to truly test the psu is swap with another or take it apart and test each component and circuit with a multi meter