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ASUS ROG STRIX B450-F-Gaming II -- Power LED on case won’t stay on

jj-adams
Level 7
Motherboard:

ASUS ROG STRIX B450-F-Gaming II


Problem:

To diagnose the problem I turned off the power supply and unplugged
the computer from the wall.

Here’s where it gets interesting.

When I plug the AC power into the wall (with the PS still turned off)
the power LED switch comes on and stays on.

Also, my LED keyboard also lights up and stays on.

Remember, the power supply is still turned off.

When I press the power button, the computer boots up and
the power switch LED goes out and stays out and the computer
boots up just fine.

Anybody seen anything like this?

Thanks

John
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4 REPLIES 4

schm0
Level 10
When I plug the AC power into the wall (with the PS still turned off)
the power LED switch comes on and stays on.

With PS, you mean power supply?
Did you try to flip the plug that goes into the wall socket, so that hot and neutral are switched?

I think older PSUs only cut off one wire with the switch.
When hot and neutral are swapped then maybe only the neutral wire gets cut, so technically there is still power on the supply.

To make things even worse, different countries, have different rules where the hot and neutral wires go (in the socket).
Some countries also have plugs that can only be plugged in one way into the socket to make sure hot and neutral aren't swapped. (when the socket is properly wired)
It's always better to use switches that cut off both wires.

Best example is a simple lamp with a switch which only cuts the neutral wire.
When you switch the lamp off, then yes technically the lamp is off but when you touch the socket you are dead. (when there is no fi circuit breaker (RCD)). Well maybe not when you a wearing rubber shoes and don't touch anything that is grounded. 😛
This is even worse when the hot wire is wired up to the outer part of the bulb socket.

The power supply I'm using is a "be quiet!" "Dark Power Pro 12" 1500 watts

I'm located in the USA.

I'm also using a "Brickwall" surge protector model PW2R15AUD.

schm0
Level 10
I'm not an electrician but it sound like that the PSU might be defective?
When the PC still gets power even when the PSU is turned off, maybe:
- The switch on the PSU is defective
or
- The switch only switches one wire and hot and neutral are swapped but then there needs to be some other way for the neutral to be connected to some "ground" (idk the right english term.. potential compensation?)
But when that's the case and the circuit is protected with an RCD, it should trip and cut the power.

Does the US have a regulation in place that dictates that every power circuit needs to be protected by a RCD?
Or only for "wet" rooms like kitchen, bathroom?

When there is no RCD in place I would advice not do any more experiments as there is maybe chance to get an electrical shock.

jj-adams
Level 7
jj-adams wrote:
Motherboard:

ASUS ROG STRIX B450-F-Gaming II


Problem:

To diagnose the problem I turned off the power supply and unplugged
the computer from the wall.

Here’s where it gets interesting.

When I plug the AC power into the wall (with the PS still turned off)
the power LED switch comes on and stays on.

Also, my LED keyboard also lights up and stays on.

Remember, the power supply is still turned off.

When I press the power button, the computer boots up and
the power switch LED goes out and stays out and the computer
boots up just fine.

Anybody seen anything like this?

Thanks

John


PROBLEM SOLVED !!!!!!!

I first tried switching out the power supply.......no fix.

Then, I upgraded my motherboard BIOS from v4602 to v4801.......problem solved !!!!!!!

I would just like to say thanks to ASUS tech support who made this suggestion; whereas, I
would of never thought of doing this.

John