A mismatching working laptop power supply - can do the same with my LCD?

I recently bought a laptop in a firesale for $50, the power supply the guy gave me to power this Panasonic is Dell in origin (19volt), and the PS unit is of higher voltage than the notebook yet I was not aware of this and the notebook (Pana Toughbook old P3, 15.6volt) runs fine for days and continue to do so, was... show more I recently bought a laptop in a firesale for $50, the power supply the guy gave me to power this Panasonic is Dell in origin (19volt), and the PS unit is of higher voltage than the notebook yet I was not aware of this and the notebook (Pana Toughbook old P3, 15.6volt) runs fine for days and continue to do so, was there some tweak before hand or am I missing something? I thought voltages must match.

My bigger question is can I somehow do the same tweaking and use a mismatching PS to power an LCD I bought from a junk dealer? The $10 junk computer/composite LCD is working I verified that with a PS needed for another LCD so can't just use that.
Update: I purposely took the battery out, for reason that previous owner killed it with too serious memory effect not this, some change of reality with this?
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