So you PHYSICALLY checked the connection of the Video Cable, TO the motherboard, TO the screen Inverter, and TO the back of the LCD screen?
Visual inspection will NOT do. If either motherboard connector, or LCD screen connector is loose, the width of this letter -> I < you won't see it, and it will affect the video signal.
The Video Cable connects to the motherboard under the Middle Cover, above the F4 and F5 key on the Keyboard. (Left edge of F4 key over to middle of F5 key)
[Middle Cover is Acer speak for Switch Cover. The cover strip above the Keyboard, and below the LCD screen ]aspire-3100-5100-5600-lcd-cable-dc020007o00-.html
Click on the view to enlarge. Top left side connects to the LCD screen. Rectangular Black connector with thick round cable, at the bottom, connects to the motherboard. Small cable coming off at the bottom, connects to the screen Inverter ]
From the motherboard connector the Video Cable routes up under the left Hinge, and into the Display Assembly. It then connects to the screen Inverter, and LCD screen.
From normal opening, and closing of the laptop, repeatedly, the Video Cable may become pinched.
This can lead to loose connections.
It can also lead to damage of the Video Cable.
If the sheath of the cable shows apparent signs of damage, the tiny wires inside may be damaged also.
This means to ENSURE that the Video Cable is NOT the problem, a continuity test needs to be performed on all of the Video Cable's wires. (OHMS)
If an economical multimeter ($5 to $12) is not available, suggestion is to take it down to the nearest 'Mom and Pop' computer store, and have them check it. Labor charge should only be a few bucks.
Video Cable checks out it's on to the screen Inverter, for the diagnoses.
This diagnoses is for an Acer Aspire 5100 Notebook PC. Uses a single (1) CCFL for a Backlight, and has a screen Inverter. Laptops that use LED's for a Backlight generally do not use a screen Inverter]
Did you test the screen Inverter, or replace it?http://www.amazon.com/Acer-Aspire-5100-Inverter-PK070005U00/dp/B005F1N5O2http://www.fonerbooks.com/test.htm
Takes a sensitive multimeter. Read fairly expensive.
An LCD screen cannot produce light by itself,http://solutions.3m.com/wps/portal/3M/en_US/NA_Optical/Systems/BehindTheScenes/Optics101/
Click on the monitor. Suggest start out with your audio turned down ]
It needs an additional light source.
A Backlight is the additional light source.
A Backlight can be a CCFL, (Or two of them), or a series of LED's.
(Light Emitting Diode)
The Acer Aspire 5100 Notebook PC uses a single (1) CCFL.
A CCFL is a Cold Cathode Fluorescent Lamp.
Similar to Fluorescent lighting used in homes, and businesses, but on a MUCH smaller scale.
[Average thickness is 2mm. That is a little larger than 1/16th of an Inch.
Average length is almost as long, as the LCD screen is in height,http://www.laptoprepair101.com/laptop/2007/12/09/replace-laptop-backlight-ccfl-lamp/
A screen Inverter is used to convert the power (Electricity) from the laptop, for the LCD screen, and Backlight.
90 PERCENT OF THE TIME the fault is a bad screen Inverter.
If the screen Inverter is good, the LCD screen is bad.
[The LCD screen, and the screen Inverter are a MATCHED unit.
When purchasing make sure you get the correct screen Inverter, or LCD screen ]
For additional questions please post in a Comment.