Bang & Olufsen (HP) Omen Laptop power light flashes once but no boot

[dicky96]

Hi guys
I have a B&O Omen laptop here. It has very specific fault symptoms, hopefully someone can give me some guidance

If I plug in a known good 180W third party charger the little LED next to the power jack on the laptop flashes red once, but the laptop will not start. It will not flash red again unless you unplug and reconnect the power.

If I remove the main battery (I can't see a cmos battery) then the led by the jack does not flash when I plug in the adapter, but if I press the power on button with adapter attached it flashes once white every time I press the button, for a number of presses, then it stops flashing white until I remove and reapply the power in which case the same happens.

I tried removing the battery and holding down power for one minute - it did not help

I measured the resistance on all the buck coils, I can see two that have a low resistance around 2 ohms, and another .7 ohms, but these are right next to the GPU and CPU so this seems reasonable

If I press the power button, no battery, and measure the voltage on all the buck coils I can see every time the white LED flashes , nothing powers up, not even for an instance, unless it is too fast for my meter to react

One buck coil next to the battery connector behaves oddly.

With the power jack and battery connected it initially reads 3V but keeps dropping like a discharging capacitor, settling at about 0.75V

With power jack applied but no battery it starts at about 1.2V and climbs up like a capacitor charging, setting at 2.75V

Checking from ground to the battery connector (battery inserted, no power jack) I see 3V on one pin (5th from left) but nothing on any of the other pins

From ground to battery connector with power jack connected I see 2.7V discharging down to about 0.75V on pins 1 and 2 (from left) and I still have 3V on pin 5

Is this trying to tell me something useful, like I have a faulty battery maybe? Or something else?

Cheers
Rich

[mon2]

Re: Bang & Olufsen (HP) Omen Laptop power light flashes once but no boot

1) Which logic board # is onboard?

2) Trace the DCin connector to locate the 2 x DCin mosfets + charger IC.

3) Which charger IC is onboard? Most likely will be the popular BQ series which will drive 2 * N-channel mosfets for the DCin section.

Need to review the details of the DCin mosfets and the charger IC. Often, the 2nd DCin mosfet becomes defective.

Confirm the GATE voltage that will be common to these DCin mosfets. If all is normal, the GATE voltage should be ~25 volts and this is from the boost driver circuit inside the BQ device on the ACDRV pin.