Backlight does not come on even when the unit is plugged in. worked well for golf this afternoon....ideas?

Yes Michael.

90 percent of the time the fault is the Inverter. (Screen Inverter)

{As I'm sure you know,.......
An LCD screen cannot produce enough light by itself. It needs an additional light source.
A Backlight is the additional light source.

A Backlight is a CCFL.
Cold Cathode Fluorescent Lamp.
Similar to the Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.

An Inverter is used to convert the electrical power coming from the laptop, for the Backlight, and LCD screen }

The Inverter is located behind the Display Bezel, and at the bottom of the LCD screen, for Many models of laptops.

(Display Bezel;
The thin plastic 'frame' in the front of the LCD screen, and which surrounds the LCD screen.
Part of the Display Assembly)

If I knew the manufacturer name, and model number of your laptop, I may be able to provide a link to a free Service Manual.

For additional questions please post in a Comment.

Regards,
joecoolvette