Acer v3-551 replaced motherboard and display, laptop work perfect only on external display via VGA or HDMI, it's look that Led back-light not work as seen badly visible on dark logo when start/

How about looking at a screen?

Use an external monitor

Briefly;

Your laptop has an external display device port. (Connector)
I do not know what it is, because you didn't state the laptop manufacturer name, and model number; Elizabeth

It may be a VGA port, or HDMI port, or Mini-HDMI port; or DVI port

http://en.wikipedia.org/wiki/VGA_Connector

(Scroll down for VGA Cable example)

http://en.wikipedia.org/wiki/HDMI

(You can click on any photo, and it will enlarge)

http://en.wikipedia.org/wiki/File:HDMI_Connector.jpg

http://en.wikipedia.org/wiki/Digital_Visual_Interface

Laptop OFF, monitor OFF, connect the external display device to the laptop.
(VGA = Monitor. DVI = Monitor. HDMI, and Mini-HDMI usually = HDTV. They all compromise an external display device)

Turn the monitor/HDTV on.
Turn the laptop on.
By factory default settings, the display should show on the external display device.
IF not;

There are at least 3 display options. For this example I'm going to use a VGA monitor.
(For a VGA monitor you can use a CRT type of monitor. Looks like a small TV. Or you can use a flat LCD screen monitor, if it has a VGA Cable attached)

The basic 3 display options using a VGA monitor are;
1) Internal monitor of laptop ONLY
2) Internal monitor of laptop AND external VGA monitor
3) External VGA monitor ONLY

Hold the Fn key down, and at the SAME time tap once on the Display Toggle-Over key.

Which key is that? Dunno. Laptop manufacturer name, and ......................

It will be one of the F keys at the top. F1 through F12.
The Function key will have a monitor icon on it, and usually an arrow on one side........Or perhaps two monitor icons sitting side by side.
(Empty rectangle is a monitor icon)

Still no display on external display device?
Hold the Fn key down again, and tap once more on the Display Toggle-Over key

[If memory serves for Display Toggle-Over key;
HP = F4
Acer = F5
Toshiba = F5
IBM/Lenovo = F8

Don't write that in stone, however.......]

Once you post the manufacturer name, and model number; then I can guide you step by step.

Post back in a Comment.

Regards,
joecoolvette

Wouldn't it be NICE to know what laptop you are referring to

Oh well...........maybe one day

By factory default settings the display should automatically show in the external VGA monitor. (TV. Whatever)

HOWEVER;
Your laptop has at least 3 display options;
1) Internal monitor of laptop ONLY
2) Internal monitor of laptop AND external VGA monitor
3) External VGA monitor ONLY

By factory default settings the display should automatically show in the external VGA monitor. (TV. Whatever)

Press, and hold the Fn key down, and at the same time tap once on the Display Toggle-Over key.
Which key is the Display Toggle-Over key?
Dunno. Laptop manufacturer and model number wasn't stated.

(One of the F keys at the top.
Generally;
Acer = F5
HP = F4
Lenovo/IBM = F10
Dell = F8, unless it's Alienware - F6)

Did that? That's how it worked on your friend's TV?
Then your TV is the problem.
Settings I assume. NOT a TV tech.

Regards,
joecoolvette

Hi,

Does external display work fine? If you have not checked, connect an external display like desktop monitor or a LED TV which has VGA connector to your laptop's vga port. You may have to use some fn keys combination to switch from laptop display to external. If external display works fine then check the display cable connecting laptop motherboard to laptop display. And also check laptop LCD/LED screen. You may have to try another with another screen in such scenario.

I did not see any white lines, Simon, in the screenshot.
Just sayin'.
(Glad you tried to post it though!)

The problem is caused by a faulty Video Cable, or it's in the Display Assembly.

However, you better start the diagnoses with using an external VGA monitor, and see if the lines show up on the external monitor, also.
This would indicate a bad graphics chipset.

For most people that would mean replacing the motherboard.

A) Laptop OFF, monitor OFF, connect a VGA monitor to the VGA connector, on the Left side of the laptop.

Example of a VGA cable, and VGA port, (Connector),

http://en.wikipedia.org/wiki/VGA_connector

You can use a external VGA monitor that is a CRT type, (Looks like a small TV), or a flat LCD screen monitor with a VGA cable.

A1) Turn the monitor on. If a CRT type allow it to warm up.
Turn the laptop on.

By default the display should show on the external monitor.
IF Not,

Press, and hold down on the Fn key, (Bottom left of Keyboard), and at the same time tap on the F5 key. (Top of Keyboard)
{The F5 key is the Display Toggle-Over key }

No?
There are at least 3 display options available.
1) Internal monitor of laptop ONLY
2) Internal monitor of laptop AND external VGA monitor
3) External VGA monitor ONLY.

Hold the Fn key down again, and tap once more on the F5 key.

Graphics look good on external VGA monitor?
Your graphics chipset is good.
Problem is Video Cable, or in the Display Assembly.

B) Video Cable: (LVDS Cable)

http://www.insidemylaptop.com/disassemble-acer-aspire-7551g-laptop/

The above is for an Acer Aspire 7751G, but it is close enough to the 7750G models, and info should directly crossover.

Scroll down to Step 17.
The Video Cable connection to the motherboard, is shown by the yellow arrow at the Top Left.

Note, although the photo is less than, the routing of the Video Cable.
It goes through the Left Hinge.
(Then into the Display Assembly, and connects to the back of the LCD screen)

With normal opening, and closing of the laptop, the Video Cable could be pinched, or have been pinched. Could have been pulled on.

You close the laptop, the cable is slightly pinched in the Hinge, and it pulls loose from the motherboard connection, AND/OR the LCD screen connection.

Doesn't take much of a loose connection. In fact it's hard to discern with the human eye, sometimes.
Make sure this motherboard connection is tight.

You have to open the Display Assembly, and check the Video Cable connection on the back of the LCD screen.

Doesn't look loose? Try to plug it in tighter anyway.

Check the connection of the wire/s from the Video Cable, TO the screen Inverter.
The small circuit board behind the Display Bezel, (LCD Bezel), and mounted to the bottom of the LCD screen.

When on the motherboard side, the side of the Video Cable that runs through the left Hinge, is there any apparent damage? Damage to the sheath of the Video Cable?

If there is, chances are the tiny wires inside the Video Cable, are damaged also.
Check with a multimeter. Perform a continuity test of Each wire.

C) Display Assembly:
Video Cable checks out then the problem is in the Display Assembly.

1) Screen Inverter:

http://www.sparepartswarehouse.com/Acer,Aspire-7700-thru-9800,Laptop,Inverters.aspx

http://www.insidemylaptop.com/replace-broken-screen-acer-aspire-5745g-laptop/

Not your model, granted. Posted for the Display Assembly dis-assembly pictorial guide.

Primer:
An LCD screen cannot produce light. It needs an additional light source.
A Backlight is the additional light source.

A Backlight is a CCFL, or a series of LED lights.
Your laptop uses a series of LED lights for the Backlight.

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

A CCFL requires a screen Inverter.
A screen Inverter converts the power from the laptop, for the Backlight, and LCD screen.

NOT all LCD screens that use LED lights as a Backlight, use a screen Inverter. I suspect yours does not, as I can't find a listing for a screen Inverter, for it.

http://www.laptopscreen.com/English/section/FAQ/1245191276/Correct%20backlight%20type%20for%20your%20new%20screen/

This would mean that if the Video Cable proves to be good, the next step is to replace the LCD screen.

Shop around for the best price, AND make sure it is a direct replacement for yours.

Regards,
joecoolvette

Diagnose the problem one step at a time.

1) Does the Power On LED light come one, and the Harddrive activity LED flashes?
Hear the fan running?

Attach an external monitor to the laptop. See if you get graphics on the external monitor.

If so the problem is in the Display Assembly. More on that in a minute.

If Not, the problem is the motherboard. The graphics chip may be faulty.
(If so the usual culprit is a loose mounting of graphics chip to motherboard )

You can use a VGA monitor for an external monitor. Another term is CRT monitor. Looks like a small TV.
OR, alternatively if you have an LCD flat screen with a VGA monitor cable, you can use it.

http://en.wikipedia.org/wiki/VGA_connector


1) Laptop OFF, monitor OFF. Plug the VGA cable of the monitor into the laptop's VGA connector.
(Back of laptop)

Turn the VGA monitor on, let it warm up. Now turn the laptop on.

No display shown on the external monitor?
Press, and hold down on the Fn key, (Bottom Left), and tap once on the F5 key.
(Display Toggle-Over Key)

Still no?
Tap once more.
There are 3 options;

1) Just the display screen of the laptop
2) The display screen of the laptop, AND the external monitor
3) Just the external monitor



A) Display on external monitor?
Problem with the Display Assembly. (Acer = LCD Module)

The Display Assemblies main parts are;
1) The Display Cover. The cover that surrounds the LCD screen (Acer = LCD Cover)

2) The Display Bezel. The thin plastic frame in front of the LCD screen. Looks like a picture frame.
(Acer = LCD Bezel)

3) The LCD screen assembly. {An LCD screen is composed of layers} (Acer = LCD Panel)

4) The screen Inverter circuit board

5) LCD Panel brackets (2)

6) Video Cable (Acer = LCD Cable)

7) Hinges {2}
Plus various screws.

Primer:
An LCD screen does not produce light. It needs an additional light source.
The additional light source is a Backlight.

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

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

90 Percent of the Time the Problem is the Inverter

Acer TravelMate 4000 series of Notebook PC - Service Manual (Free)

http://www.tim.id.au/blog/tims-laptop-service-manuals/#toc-acer

Scroll down to the Travelmate heading.
Go down to the 4th line (Begins with 3230), and scroll across to 4000.
Left-click on 4000.

After you click on the file name (4000) it may take up to 30 seconds before the first page comes up.
It may also take additional time for the file to fully download.


B) No display on external monitor?
Problem with the motherboard.
Most generally the graphics chipset.

(ATI Mobility Radeon 9700 chipset,

http://en.wikipedia.org/wiki/Comparison_of_ATI_Graphics_Processing_Units#Mobility_Radeon_Series

Chip and Chipset are slang terms for I.C.
Integrated Circuit,

http://en.wikipedia.org/wiki/Integrated_circuit )

The graphics chipset is mounted to the motherboard via a BGA surface mount.
(Ball Grid Array,

http://en.wikipedia.org/wiki/Ball_grid_array )

To explain a BGA surface mount;
The older Intel Pentium 4 processors that used a Socket 478 processor socket, had contact pins on the bottom of the processor.

A chipset using the BGA surface mount does not have contact pins.
It has Solder Balls in place of the pins.

There is no socket with socket holes. There are Copper Pads.

The chipset is set into place with the Solder Balls lining up on the Copper Pads.
Then a specified temperature, and specified length of time is used to melt the solder balls.
This solders the chipset to the Copper Pads, which in turn solders the chipset to the motherboard.

Excess heat, due to the laptop is overheating, can partially re-melt the solder connections made, and cause a poor contact.

May be caused by the laptop is dirty inside, and the cooling capacity of the cooling components, has dropped tremendously.

May be due to a poor cooling system design in regards to the graphics chipset.

The cooling system may be adequate enough to keep the Processor within it's specified temperature operating range, (Thermal Limit), but NOT adequate enough to keep both, Processor AND graphics chipset cool.

Using the HP Pavilion dv9000 series of Notebook PC, this video gives information on the problem in more detail,

http://www.youtube.com/watch?v=bnkQNmKauEc

For additional questions please post in a Comment.

Regards,
joecoolvette

If the display works fine when connected to external screen via VGA connector then then the problem is either with the LCD display panel ( which consists of the display panel and inverter ) or the LCD cable that connects the LCD to the motherboard. You could try to re-seat the cable connection on the back of the LCD panel.

Most Acer laptops have a Blue VGA Port for external monitor hookup. Does your TV aslo have such a port (most newer models should)? If so connect these and change display settings on Laptop.

Try testing it out through your external ports like the vga, svideo (hdmi if you have one) port to a external monitor, or a tv and see if you get anything there. If you are able to get display to a tv, or external monitor through your external port, then you might have a issue with your screen inverter, or loose connection somehwere between your screen and your laptop base. Secondly if you can't get a display to a tv or external monitor using the external ports, or you get the same display like your screen, then your vga chipset is screwed, and you motherboard will need replacement since the vga chipset is solder onto the motherboard. At this point you can either try to replace the motherboard, (which is going to cost you almost or more then a brand new laptop) or decide to go ahead and get a new laptop.

Theres is a lot of reason associating to a black screen. First lets just assume it the screen and not the laptop. Check to see if you still see any image in the screen, you might want to do this in a lighted area. If you do, but is very dark, then your backlit light is dead and your screen needs replacement. If you don't see anything, then use a external monitor such as a computer monitor, a Tv and connect via VGA port, or HDMI if you have one or a svideo to an external souce and see if you get picture, If you do, then your Inverter is bad, or either a loose connection wiring somewhere between your comuter base and your screen. ( Because laptop tend to open and close alot) If you don't get anything via external source through your VGA, HDMi or s-vdeo, then this is something involved with your laptop. Could be from cpu, chipset, ram, or simply the motherboard itself.

To make sure what is really wrong we need to break down couple of things, have you tried connecting a external source such as to a monitor or a tv via s-video or vga. If it is able to display to the external source then there is something wrong with your screen. Now is it completely dead and you cannot see anything or are you able to see something but the display lights are not litting the display. If that is so, then your backlit is dead and you will need to replace the entire screen. In my honest opinion if that is the case I recommend you to by a new laptop, because parts/labor cost would cost more then your medium powered new laptop.