advice on diagnosing

[dtr146]

I have an older hp laptop and the back light does not function anymore (hold light up to screen and see items). i cleaned the board because i noticed corrosion but now i have no display. My only question i need answering is if a laptop does not post will the caps lights and num lights still function (by enabling and disabling it) because mine do and i dont have a monitor. 

[Windows7ge]

Caps lock, Num lock, Scroll lock, they function independently from the status of the OS. It's when you make an input (press a key) that the status of these locks will alter how the system receives the signal that a button was pressed.

 

Really, in theory you should be able to plug +5V directly into the keyboard and it'll behave like nothing's different.

 

Although this logic might be flawed as I have had instances where having a system crash made even the lock keys unresponsive. (LEDs remained lit/unlit)