Starting up just the 'naked' logicboard

I have a logicboard laying around and would like to test / verify it's functionality.

In my test case, there is following connected to the board:

- Fan

- DC-IN

- Screen-Adapter (for getting some feedback)

- Speaker, left (for getting some feedback)

- RAM (optionally, to trigger "RAM Missing" beeps)

- HDD (optionally, to trigger some Disk-Access)

Two things happen, when the Charger is plugged in:

- Fan begins to start automatically, runs continuously. The fan runs quite silent/slow

- When the Keyboard is attached and the power button is held, nothing happens until button is released. Than the fan begins to run at maximum.

As I know this from working devices, this seems to be the the step before going to normal boot sequence.

Is this behavior already the result of a broken board?

Or is anything mandatory missing?