Sad thing just happened minutes ago...

I wrongly connect the external power supply to the Aux socket, not the DC socket because there's "IN" next to the Aux socket and "OUT" next to the DC socket. I thought IN means "DC IN" but it is not that way.

I used wire connection so the damage was even bigger. I didn't realize that until heard 2 small pop sounds. And it was too late.

Damage report:
1. 2 USB ports on the right-hand side of my Eee PC are gone. I guess that's where the pop sounds came from.
2. Maybe the wire is gone, because I can't find the /dev/ttyUSB0 when I try to connect it to the last function USB port. Need further test of the wire on my Mac..
3. I "think" the Merlin head is OK. I changed to battery power source and connect the hand control back to the head. It is still moving!

I went back and check the manual of the head and realized that the IN is Aux and the OUT is DC. And there's even a warning message:

"Never plug external power supply into "aux power" socket. It might damage the batteries inside the battery compartment or cause them leak or explode."

So I guess I was luck because I didn't put the batteries in the compartment...

Lessons learned:
1. Do not trust what you see, and always read the manual before you do anything...
2. Electronic is not for kids...?