Replacing CCFL LCD Backlights with LEDs?

[davidg5678]

Hello,

I have an iBook Clamshell with a screen that seems abnormally dim. I read that over time the CCFL backlights inside LCDs gradually dim as they wear out. I did a bit of poking about online and found some kits that seem to be able to replace the existing CCFL modules inside old displays with LEDs. There is very limited information available online, but from what I can tell, many of the kits come with a replacement LED driver board that is meant to be swapped into the place where the CCFL inverter used to be.

Here is an example eBay link for such a kit: https://www.ebay.com/itm/330mm-LED-Backlight-Strip-Kit-Update-7-15-4-CCFL-LCD-Laptop-Monitor-To-LED/272344643312?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D225074%26meid%3D752983322adc45d69af056eee7011a72%26pid%3D100675%26rk%3D1%26rkt%3D15%26mehot%3Dnone%26sd%3D184476698668%26itm%3D272344643312%26pmt%3D1%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3A26a49814-0c9a-11eb-bf7a-fa409d50a267|parentrq%3A1d49ceba1750ad32d24867c4ffedd7c6|iid%3A1

I have included a screenshot as well, for I am sure the link will eventually die (due to the temporary nature of eBay).

I am curious to hear other people's thoughts on these LED kits. Do you think it is worth trying to replace the CCFL lights inside my laptop? Could this same technology be refitted into a power-hungry 30" Cinema Display to make it run cooler while using less electricity?

(As a side note, I just realized the title of this post has a ridiculous number of acronyms in it. I'm sure most people here know the meanings of these acronyms, but I'll define them anyway.)

CCFL: Cold Cathode Fluorescent Lamp

LCD: Liquid Crystal Display

LED: Light Emitting Diode

 

[quorten]

For my experience, one big problem is disassembling the screen to to install the replacement.  I've simply used a matching replacement panel when I had a CCFL bulb failure, though I would have preferred swapping out with an LED light.  Another big problem is mechanical compatibility such as bulb length, "inverter" board mounting and electrical connectors, so it's important to double-check this.  In the case of the 30" Cinema Display, it may be pretty tough to find a compatible replacement, but that's my guess.

Still, electrical signal compatibility with the inverter can also be a problem.  For example, this inverter that I've worked with is meant to be used in conjunction with the Samsung LTN154X3-L09 LCD screen inside my 2005 Dell Inspiron e1505, it uses a much more complicated flat flex cable for the input.  The bulb output is the two-pin connector on the left.

 

[davidg5678]

Another big problem is mechanical compatibility such as bulb length, "inverter" board mounting and electrical connectors, so it's important to double-check this.

This is a pretty good point. The listing for the product I found says that the LED strips can just be cut down to size, which in theory would take care of the bulb length issue. As to whether or not the replacement driver board would fit or be electrically compatible... I guess that would be a little bit tricky to figure out without tearing open a display. Anyone have a spare Clamshell LCD panel they'd like to donate to science? :lol:

Actually being able to take a screen apart and put it back together could be tricky too. There are many diffusing, polarizing, etc. film layers inside LCDs, and their order and orientation likely would need to be preserved exactly for things to work correctly. There is also the issue of not cracking the chuck of thin glass that is the LCD panel

The other interesting thing I noticed in the listing is that there is a "wiring diagram" for connecting the LED driver board to the LCD. It sounds like this is not necessarily standardized, but with enough free space in the chassis and an Arduino, some sort of interface conversion is probably possible. I'd assume that many computers just use a PWM signal to adjust the screen brightness, but I could definitely be wrong here. It would be kind of annoying to reverse engineer whatever crazy protocol the LCD manufacturers decided to use instead of PWM, though.

 

[quorten]

In the case of the 2005 Dell Inspiron e1505 laptop I've mentioned, I found out that it uses a MAX8759ETI IC as the "brain" of the inverter board and I've found the datasheet online.  It's capable of dimming control via PWM, SMBus (I2C), or ambient light sensor.  I wish I knew what year it was introduced... so all that said, if similar PMICs were on the market during the time of the design, I think Apple would likely use one of the most advanced ones and connect via SMBus.  The earlier PowerBooks may have been more likely to use PWM for brightness control signaling to the inverter.