The voltages you measures are the battery rail and not the main rail.
Q15 and Q31 and part of the DC to DC converter to convert the 19v from the charger to the battery voltage.
What's wrong with the laptop?
I measured this voltage on all power supplies on the board so I dont think it was just a battery rail. I didnt find 19V anywhere on the board.
Troubles with laptop were following:
-Main symptom was automatical switching ON/OFF....right after lid opening. After some period (around 10s) it switched OFF.
-Switching frequency was faster with charger plugged in.
-When started without charger I noticed that LED was blinking orange (which means battery less than 5%) but that was not true....battery was nearly full.
-Sometimes I was able to break this ON/OFF loop with chaotic pressing of power button. Laptop was running fine without any load but after some load applied (I guess) it shutted down.
-
When charger was plugged in LED was solid white and I noticed some regular interrupts for a milisecond (like some driver restarting)....this looks OK now. -Symptom above was not correct. Those interrupts are still present. But as manual says...it should be "slow blinking"...which signalizes battery 20-80% and still charging. Instead of this slow blinking there are those fast interrupts. The same happens when battery is 2-20%...just colour of LED is amber.
Of course I have measured nearly zero voltage on power button. During my investigation I was probing with power supply on various places looking for any short. After this probing (probably after probing on power button) I noticed there is already correct voltage on the power button so everything looks to be OK now.
But Im not pretty sure with that low voltage on power rail. Its still without heatsink so I didnt try to load it yet. Tried to assemble it and load it...everything looks to work fine instead of that charging LED blinking.
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