Trouble shooting : Laptop

Symptom:
My laptop works fine without AC adapter. It acts retarded with AC Adapter connected.
It works fine after putting a book on the one side of the AC adapter, so with some weights on the AC adapter, the laptop works fine.

Diagnosis:
Motherboard problem (common problem in the same series)
or
AC adapter problem (potential cause for the motherboard problem).

Test 1:
to see whether it's the problem from ac adapter.
-> Change a new AC Adapter.

If Test 1 works, hallelujah.

If test 1 fails,
Test 2:
to see whether it's the motherboard's problem or the combination.
-> Ship the laptop to the factory.
It will cost another 2 weeks to say hallelujah.

Pray for the motherboard of my laptop.
:)