A common cause is the inverter, and or the backlight failing. These are best
to replace together. In the case of buying a used one, there is a good
chance the one you buy is also defective. They only go so many hours and
they have to be changed.

With some displays, the backlight is an integral part of the display. In
this case, both the inverter and complete display should be changed at the
same time. I would not buy used parts, because they do wear out after a
number of hours, and used parts have hours put on to them.

--

Jerry G.
=====

"kk" wrote in message
oups.com...
I have a Compaq Presario 1700t laptop, the 13.3" LCD is not functioning
correctly.
When I turn on the laptop, the LCD is very dark but still can see the
dim image of the Windows is booting up. Then I research on the problem
and opened the case and find the inverter is ALPS KUBNKM011A. I ordered
the inverter from ebay and replaced the old inverter. However the
problem still exist. I found there is no difference on the dim image
whether plug in the inverter or unplug it from the montherboard.
I tested there is 12v dc output from the red wire but nothing from
white and green in the middle. Also, no voltage (no dc nor ac)from the
socket where the pink wire supposed to plug in.
Could anybody help me how to test whether the inverter or backlight or
video board having problem?
Thank you!!

The inverter looks like this
http://www.impactcomputers.com/198700-001-ib.html#