HP L20486-004 Pavilion 24-xa0181na Board not Powering ON

[Rabit007]

Hi

I get myself mainboard from HP Pavilion 24-xa0181, part number L20486-004, to try build Passive mini PC.

But board do not powering on.

From my understanding to power on I need short 3.3V + GND on 4pin connector for Power button to start board.

I checked Voltages 3,3V 5,0V and 19,5V is present also led next to power jack is on, and KBC getting 3.3V.

Any idea why board is not powering or what to check next ?

[itsmyname]

@Rabit007 -- see the image: jump-start-motherboard-w-450x378.jpg.webp (450×378) (pcguide101.com)

The image shows the label "+PW-" and a metal screw-driver briefly(!) connecting two pins in that block of pins.

Is that what you are trying to do?

[Rabit007]

Yes but this is not ATX board and I not sure if this will be enough

[itsmyname]

@Rabit007 -- I see the white-coloured socket for an Ethernet cable, but what is that black-coloured "inverted-U" element on an angle vertically above the connector that is immediately to the right of the Ethernet socket?  

Is that connector immediately to the right of the Ethernet socket a plug where the external power-adapter cable would connect?

Along the top edge, I see the 4 possible connectors for ribbon-cables, and a black-coloured socket for an M.2 memory-stick. Perhaps, one of those ribbon-cables leads to the ON/OFF button ?

[Rabit007]

I borrow power button from other AIO I getting flashing led - if I correctly indication that I need plug inverter ho to by pass it, I need resistor or shorting some pins on inverter socket ?

[itsmyname]

@Rabit007 -- compare the power switch to a multi-function flash-light:

• tap its on/off button once, to light-up the flashlight's lamp,
• tap it again to make the lamp "blink",
• tap it again to turn the lamp off.

For your power-switch, it is normally an "open" circuit -- no power can go through it.

If you allow the two wires to very-momentarily touch, it closes the circuit, and the motherboard powers-on.

If you allow the two wires to touch for a few seconds, the motherboard puts the computer into "sleep" mode.

If you allow the two wires to touch for more than 10 seconds, the motherboard immediately powers-off the computer.

So, take the two "power-button" leads from the motherboard, and briefly "tap" them together, to power-on your motherboard. No need for any "resistor" nor "invertor".