Problem while Extending Notebook LCD

carpanther · 09-06-2007, 04:43 PM

Hello everyone,

Sorry to bother you with this, but I don't know where else to turn.
I've read some threads regarding notebook lcd extension, so I thought I'd give it a go...

There were two cable bundles, the first one contained about 11 different colors of wires, I suppose the VGA signal?

Unfortunately the second bundle from which I thought the wires were also color-marked...

contained about 14 identical darkblue wires and 2 red ones.

> Could this be the power signal to the invertor or am I being too optimistic

> Should I try reconnecting them to see what happens or could I cause damage to the mainboard?

Thanks for your responses!

Fred

bbalazs · 09-07-2007, 12:59 AM

What type of notebook do you have? Old or new, display size?

Notebooks do not use VGA for LCD, rather LVDS (totally different, digital signaling)

Have you got a multimeter, soldering iron or any skill in electronics?

carpanther · 09-07-2007, 06:15 AM

First of all, thanks for your reply

It's a rather old notebook, a Mitac 8080 (1.3 Centrino, about 4 years old). The display is 15" 4:3 format, maybe 14.1" but definately not smaller.

And I have a multimeter, and soldering iron (already soldered a power/on off extension to the mainboard switch, cpu fan always-on bypass).

The thing I am confused about is the second wire bunddle which contains about only darkblue and red wires. Can I randomly reconnect them, or is that a bad idea?

I try to post some pictures in a couple of hours.

Thanks,
Fred

Quote: Originally Posted by bbalazs

What type of notebook do you have? Old or new, display size?

Notebooks do not use VGA for LCD, rather LVDS (totally different, digital signaling)

Have you got a multimeter, soldering iron or any skill in electronics?

Rob Withey · 09-07-2007, 06:25 AM

Quote: Originally Posted by carpanther

Can I randomly reconnect them, or is that a bad idea?

That is a bad idea. Do not randomly reconnect them, you should reconnect them to the same place they were before.

carpanther · 09-07-2007, 07:21 AM

Hi Rob,

Yeah I thought so, but the thing is,
I don't know how they were originally connected.
When cutting the bundle I supposed they were also color-marked and turned out to be wrong

Is there any way I can correct my mistake?

Thanks for your help!
Frederik

Quote: Originally Posted by Rob Withey

That is a bad idea. Do not randomly reconnect them, you should reconnect them to the same place they were before.

Rob Withey · 09-07-2007, 07:44 AM

Perhaps buy a new cable from ebay or something?

carpanther · 09-07-2007, 07:55 AM

Didnt find anything on ebay, just on this site:
http://www.laptoprepairparts.com/par...ategory=cables
Though they charge like $79 :s

Quote: Originally Posted by Rob Withey

Perhaps buy a new cable from ebay or something?

bbalazs · 09-07-2007, 10:55 AM

Ok do not panic

Is this cable a ribbon cable or just a bunch of thin wires?
How many wires do you have alltogether?

First you have to determine Ground (GND). At least two will be ground.
On the lcd side gnd is on the metal house (frame).
On the laptop side it is connected e.g. to the serial port shield.

As you said it is two separated cable collection.
I suppose one of them will be the backlight, other one is for driving LCD.
Disassemble the lcd plastic frame (by removing screws - usually at the corners, often covered by small rubber or plastic discs. Then use a switchknife with wide, thin blade (eg. a Swiss army knife) and open the plastic frame. Then four screws are fixing the display (depending on the model it can be on the sides or can be directly visible) Remove them, and from this point every step must be performed very carefully, because the display can suddenly fell out and crack (better to use a sponge or a cloth on th surface avoiding any damage of the display).
Remove the display and turn it upside-down. On the PCB side you can determine the origin of the wires at the connector. Try to seek the datasheet of the display for identification. In any other case, the rule of thumb: Identify the GNDs first, power then and finally signals.
I stongly believe that LCD works with 3.3V
Next part is coming soon.

bbalazs · 09-07-2007, 11:22 AM

Generally, the connector pinout on the LCD is:
1 Power
2 Power
3 GND
4 GND
5 Signal1-
6 Signal1+
7 GND
8 Signal2-
9 Signal2+
10 GND
11 Signal3-
...and so on
..
xx GND
xx GND
Last two pins are GNDs
You have to measure a resistance about 100 Ohms (80-120) between two signal pairs (eg. Signal1+ and Signal1-).

On the laptop side, the layout is somehow similar. Identify GNDs firstly, then measure all lines voltage UNDER OPERATION (use the VGA output for displaying normal image). You can measure 3.31 or a little bit less.
Try to load it with a resistor (about 50 Ohms) for a second and the voltage should not be lower than 3.2V. That is the power line.
The signal lines are giving about +/- 0.3V.
I have no idea how to determine the order of the signals, but I think it must follow the order of the connector on the LCD side.

BACKLIGHT WIRES on the side of LCD:

Start with the GND identification, the largest metal part is usually GND. It is simple. The power line is protected by a very small SMD fuse, marked as F1 on the PCB of the backlight panel (after disassembling of the display it is an obviously separated unit directly under the LCD unit).
The backlight needs higher voltage (about 12V). It also uses an enable signal (TTL - 5V) and a signal for controlling the brightness (it can vary 0-5V or sometimes 0-2.5V according to the engineering).
Enable signal often leads directly to an SMD transistor base (or sometimes via an SMD resistor that often marked with white numbers). The brightness signal is usually lead into a SMD capacitor (has different color, usually light brown or purple) and a resistor serial and to the IC of the backlight unit.

Most important thing: DO NOT CONNECT THE BACKLIGHT POWER LINE TO THE LCD!!!! IT IMMEDIATELY KILLS THE PRECIOUS DISPLAY!

Try to resurrect the backlight unit first (you can do it separately). In that case the enlightment is visible, but of course there is nothing on the screen yet - just white void.

Then connect the gnd and power of the LCD. Then try to connect the signal lines. I think there is no real danger of connecting the SIGNAL wires randomly.

I hope this helps.

carpanther · 09-07-2007, 02:17 PM

Bbalazs,

There are two bunches of wires,
1. the colored ones -> no problem
2. about 10 identical dark blueones, and 2 red ones

Quote: Originally Posted by bbalazs

Ok do not panic

Is this cable a ribbon cable or just a bunch of thin wires?
How many wires do you have alltogether?

First you have to determine Ground (GND). At least two will be ground.
On the lcd side gnd is on the metal house (frame).
On the laptop side it is connected e.g. to the serial port shield.

As you said it is two separated cable collection.
I suppose one of them will be the backlight, other one is for driving LCD.
Disassemble the lcd plastic frame (by removing screws - usually at the corners, often covered by small rubber or plastic discs. Then use a switchknife with wide, thin blade (eg. a Swiss army knife) and open the plastic frame. Then four screws are fixing the display (depending on the model it can be on the sides or can be directly visible) Remove them, and from this point every step must be performed very carefully, because the display can suddenly fell out and crack (better to use a sponge or a cloth on th surface avoiding any damage of the display).
Remove the display and turn it upside-down. On the PCB side you can determine the origin of the wires at the connector. Try to seek the datasheet of the display for identification. In any other case, the rule of thumb: Identify the GNDs first, power then and finally signals.
I stongly believe that LCD works with 3.3V
Next part is coming soon.

bbalazs · 09-07-2007, 02:24 PM

Are you sure, that they are different?
The red color increases the possibility being power wire and the dark blues could be GNDs.
You have the multimeter, you have the key solving this mistery

carpanther · 09-07-2007, 02:33 PM

I'll try first thing in the morning and will let you know

Thanks a lot for your detailed info, appriciate it.

Cheers,
Fred

Quote: Originally Posted by bbalazs

Are you sure, that they are different?
The red color increases the possibility being power wire and the dark blues could be GNDs.
You have the multimeter, you have the key solving this mistery