Klickety-klacky HB-75P =P

That is the cassette relais you’re hearing.

Type MOTOR ON and MOTOR OFF in Basic to make it click. I think you can use just MOTOR to toggle it.

It shouldn’t ‘click’ on start-up though. It usually only happens when the computer refuses to boot for some reason , but that doesn’t seem to be the case here. If the MOTOR commands don’t work, there may be an issue, otherwise it’s probably fine...

I have a HB-75P at home btw (@work atm), I don’t use it often but I don’t recall the relais clicking when I turn it on.

No, the MSX has a relais inside to control the motor of a cassette recorder. It doesn’t matter if you’ve actually connected a tape recorder.

Have you tried the MOTOR Basic command? Does it click?

Oh, didn't know about that. o_O

I'll try this evening, thanks again! =)

The good old casette relais click
It can be handy. When at the end of a BLOAD it makes clack, you know the file finished. A hint that a hang may be about something else.
On reset, it looks like the hardware is active high. Then a tenth second later the bios makes it low again. Giving it a typical reset sound.
So there is nothing to worry about these noises. When it reacts to typing "motor" in BASIC, the case is clear.

I don´t remember my HB-75P doing any non-standard sounds. I used it last time few years ago, so I cannot be sure though.