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Sunday, May 5, 2013

Laptop Screen Back-light converted from CCFL to LED

I wonder if I could do this. I have an IBM Laptop with a bad Screen. Maybe I could Replace the IBM Screen with an Acer Screen, that I have. The Acer wont Power up. So, I'm not sure what it wrong with it. I've tried to power it, with my Bench Top Power Supply, that I built from two PC PSU's. But, I may not be getting the right voltage and amperage. I need a proper Power Supply and connector, to make sure, that the Mother Board is Bad. The Acer is probably not and LED Screen, though. Still, I find this a very interesting article...


LED backlight conversion. By Lee Davison.

I have an Acer laptop that was missing a display and had found all the bits I needed except for the CCFL backlight inverter. I'd thought I had some spares from other dead Acer laptops but it turns out they're all just a little different.
So it looked like I was going to be waiting for the correct inverter to show up until I remembered I have a few smashed LCD panels with LED backlights that I have collected for the LEDs.
How hard can it be to use the LED backlight instead?
LED backlight circuit.
Once the DO NOT TOUCH! tape has been removed from the the back of the LCD it is usually quite easy to identify the LED backlight driver circuit on the PCB.
In this case it is right next to the backlight ribbon connector, seen on the left, and has helpful legends next to usefull test pads such as LED_EN and VLED. It also has the largest inductor and schottky diode on the whole PCB.
Removing the PCB.
To remove the PCB from the smashed LCD the flex PCB connections to the glass need to be removed. These are not fixed very firmly and can usually be pulled from the PCB by hand.
If they won't let go they can just be chopped through with scissors or a knife.
This should free the PCB so it can be removed from the LCD.
Removing the LED strip.
The LED strip is usually secured by more tape, both along the length of the connecting flex PCB and along the display edge, and a couple of screws, one at either end of the strip.
LED driver chip.
I haven't managed to locate the correct datasheet for the LED driver chip, U401, used on this board but this one seems to have the same pinout so I used it as the reference in this case.
If you can't find the exact datasheet for a particular chip you can often find the datasheet for a related chip from the same manufacturer.
The circuit on the board was traced to confirm the punction of the labeled pads. The boost converter part of the circuit looks very much like the circuit in the datasheet.
Preparing the PCB.
Apart from the supply and control inputs a ground connection is also needed. A point on the PCB where ground is exposed or the ground end of a component could have been used but it was just as easy to scrape away a small patch of the solder resist from the ground trace.

Last page update: 26th April, 2013.



Miscellania. (Odds & ends). By Lee Davison.

  • HP-GL Viewer
    See what all those *.plt files look like.

  • Beginners' circuits
    A series of circuits that can be built on a small breadboard.

  • CPLD Projects

  • Making things with programmable logic.

  • Neon heads/tails
    The first project I ever finished.

  • High voltage

  • Lighting up cold cathode tubes.

  • LazyPROM

  • I got fed up waiting for EPROMS to erase.

  • PanoCAM

  • An idea for a 360 degree panoramic camera.

  • SpeedDome

  • Making a PTZ camera pan, tilt and zoom.

  • On light

  • Psuodo random LED sequencer.


  • Power supply for vacuum fluorescent displays.

  • ESR meter

  • A meter for testing electrolytic capacitors.


  • An improved vacuum fluorescent display PSU.

  • 13.8V PSU

  • A simple, linear bench PSU.

  • Charger

  • A more universal battery charger.

  • Battery pack

  • A battery pack gets shrink wrapped.

  • LED backlight

  • A laptop gets a backlight change.

  • KDF 9 Nesting stores
    Images of memory from this 1960's computer.

  • Schematic artwork

  • Just how do I draw those schematics?

  • Sampled sound card

  • Decoding the samples.

  • RS232

  • port pinouts. Because I keep forgetting.

  • Compukit

  • Bet you thought they just made the UK 101.

  • Recycling

  • Sometimes it just has to be done.

  • Not working?

  • Sometimes it's not your fault.

    Laptop Screen Back-light, converted from CCFL to LED
    LED backlight conversion
    Laptop backlight converted from CCFL to LED

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