HP 14-bf054sa - weird power button issue

[dfear]

- forum postHP 14-bf054sa
LA-F301P Rev 1.0

This laptop came in with a number of minor issues (Screen with black bar and battery that needs replacing). The laptop also had issues relating to salt (water/air) corrosion, having been used near the ocean.

The HDMI port, 2x usb ports and the SD card reader all needed replacement as they had been affected by salty air and only work intermittently. The HDMI port, 2x usb ports and the SD card reader have been replaced and have been checked for (obvious) shorts.

The laptop now fails to turn on (normally). The led on the dc socket is on when a charger is connected. When the power button is pressed the led on the charger briefly goes off, but the laptop does not turn on and there is no fan spin.

I have checked the power button and it functions ok (simple continuity test).

This is where things start to get a bit weird and interesting.....

If you look at the photo of the power button area, there is a jumper wire from the power button to a nearby pad. I added the wire as an attempt to solve the problem i am having. The wire makes no difference to the problem, before you ask.

What happens is:
1) if you press the power button normally the laptop won't turn on.
2) If you touch the wire (connecting the pad to the power button) or the pad itself, with a METAL object (tweezers or unplugged multimeter probe) then press the power button (with a finger or spudger), the laptop will turn on normally.

The metal implement is not touching any other part of the motherboard and is not connected to any other device.

My question is: How do I fix this problem, I am stumped?

[Stevedb]

Re: HP 14-bf054sa - weird power button issue

Does powerbutton resistance goes to zero when you press. Otherwise replace the button.

[dfear]

Re: HP 14-bf054sa - weird power button issue

Does powerbutton resistance goes to zero when you press. Otherwise replace the button.

I presume so, I have checked the power button on continuity mode and the multimeter goes BEEEEP! (so I take it the "resistance goes to zero"?).

I will check tho.

[dfear]

Re: HP 14-bf054sa - weird power button issue

Hi folks

I have repaired this motherboard.

*** This is a lesson for all of uses who fix motherboards, beginners and seasoned pros too.

The lesson:
Take detailed (clear & hi-res) photos before your start working on a motherboard. Take photos of not just the components/parts you are working on, but the area around it too.

The FIX:
"Simply" replace the missing components. See the attached photo. I was missing: 1x 100K 0402 resistor, 1x 110K 0402 resistor, 1x 0 ohm 0201 resistor and 1x 100nf 0201 capacitor.

I spent far too much time working on this board. My base assumptions were incorrect. I bought a spares or repair to help me figure out the solution and noticed that several components were missing from the board I was working on. I found a photo of the same motherboard (same part and revision numbers, along with a very similar configuration) online and this confirmed that I indeed was missing components.

I replaced the missing components and now the board works ok.

p.s. Logic probes are useful tools; didn't know I needed one.