Close.
A battery with Lithium/Iron Disulfide chemistry.
New ones have an open circuit voltage of 1.8 volts.
And your powering the CMOS reference input of the adapter, which is approximately zero load.
One example: Energizer Ultimate Lithium.
(in AAA and AA sizes).
That test point mentioned in the directions is part of the screen's front light circuitry.
Which I suppose you still have unplugged.
I really should go searching that motherboard for a better reference source - whenever the front light goes out, the adapter stops adapting.
