My laptop is suddenly dead, cannot determine the reason

My Dell Precision 5510 from 2016 suddenly won't power on (completely dead).

It used to work normally until couple of months ago, since when it just wouldn't power on. No light on a power button, no sound, no fans spinning, no text on display.

Previously, there was no warning signs of any problems, except maybe for a power button, I needed to press it a little bit harder then usual, but that was the issue forever.

What I did so far:

1. Checked charger voltage, it is 19.4 V, very close to declared 19.5 V.
2. Wiggled cable, checked that the charger is fully plugged in
3. Removed the base cover, removed some dust around the fans (there was some built up, but not too bad)
4. Removed the battery and charger, pressed power button for 1 min
5. Attached battery back, without charger, still dead
6. Attached charger, without battery, ditto
7. Removed one RAM module (out of two), then removed the second one, swap their places, etc, no luck

Any suggestions how to proceed from here?

Hi @oldturkey03,

My battery connector have have 12 wires: 4 red, 4 gray, and 4 black (left to right).

When charger is unplugged, and battery connected to the board, on battery connector I read 11.8 V on red wires, zeros on all others:

When battery is disconnected, I cannot read any voltage. I tried to probe on the back of the connector and on the bottom:

When I connected charger, I noticed two LEDs below the touchpad started to glow for a second, then turned off again.

With charger connected, on DC connector on motherboard, I read 19.4 V (three red wires), 3.3 V (grey wire).

When charger is connected and battery connected too, on battery connector I read 12.6 V (red wires), and 3.3 V (first two grey wires). Other two gray wires are on 0 V. I don't know if this is expected or not.

LEDs I mention before turned on for couple of minutes, then turned off again.

My understanding so far:

1. Battery is fine
2. Charger is fine
3. Charger connector is fine
4. Battery is charging

Could it be that the power button is damaged? That laptop is fine, but I just cannot turn it on?

I was unable to fix this myself so I took laptop to a service. The repair guy said that the power button is ok, but the two controllers that are orchestrating the powerup sequence needed to be replaced and one of them needs to be reprogrammed.