Precision M4600 not powering up

Dear Dell community,

yesterday my M4600 just went off during work, and since then I cannot power it back on.

What I have tried:

• AC only,
• battery only,
• AC + battery;

In all three combinations:

• push power button,
• hold Fn key + push power button,
• hold D key + push power button;

all with no positive feedback. Laptop stays off. Usually, there is a white LED on the left side, and directly after pushing the power button, the fan should do a few turns. Nothing happens.

Now I have removed the CMOS battery and re-tried the steps outlined above; again: nothing.

When AC is connected, I read 5 V at the battery connections; AC adapter works fine with other laptops.

Any further suggestions?
Thanks in advance – osti42.