Can the color of LCD backlight bead be changed? - Page 1
Forum section: electronics / repair

author: daisizhou
author_rank: Super Contributor
timestamp: September 30, 2025, 02:37:11 am
content: This is the backlight panel of an L4044 LCD module.On the host, it is connected to a 2W2 ohm current limiting resistor,The voltage at the front end of the 2 ohm resistor is 4.96v, and the backlight positive voltage is 4.04vI disassembled the backlight panel and found that it is composed of 96 yellow LED light groups, 2 of which are connected in series and 48 groups in parallel.My plan is to replace it with a 0603 packaged white LED,Because I think the white backlight looks very clear.The white LED's operating voltage is about 2.7V. I think the 2 ohm resistor may need to be adjusted.Is my plan feasible? There is no problem with welding, but I am worried that the working current may not meet the actual requirements.

author: coromonadalix
author_rank: Super Contributor
timestamp: September 30, 2025, 09:17:04 am
content: a 4044 should be standard 44780 driven just buy one in the color you want ... some can have the led backplate changedit would be more economical and less time consuming and you're sure you wont bust the leds if you overheat them

author: daisizhou
author_rank: Super Contributor
timestamp: September 30, 2025, 12:00:07 pm
content: Please see the picture, the LCD module looks like 4004, but the model seems to be labeled SIIL4044The original backlight board has a current of approximately 235ma at 4.04v.A total of 96 LEDs,I remember that the normal working current of the white LED in 0603 is about 20ma, so the total current is about 20ma * 48=960ma. I don't know if this modification is feasible

author: fenugrec
author_rank: Frequent Contributor
timestamp: September 30, 2025, 01:58:17 pm
content: modern white LEDs are very bright, I'm fairly sure 96 * 20mA will be excessive.You may run into problems of not enough voltage if wiring 2 in series (2 * Vf > your supply voltage).Anyway that's a lot of work just to change color... recommend trying to find a replacement with the color you need instead, as suggested.If you really insist on doing this, buy some white LEDs, remove 2 originals that were in series, install one white and one resistor, and experiment with resistor value to match brightness.Maybe you can get away with replacing half of the LEDs if their beam width is wide enough.

author: Zoli
author_rank: Frequent Contributor
timestamp: September 30, 2025, 02:25:50 pm
content: Quote from: daisizhou on September 30, 2025, 02:37:11 amI suppose that the display is powered from 5V. In this case, connect two white LED's in series, and test how they behave@5V; most likely you won't need any resistor in series.

author: Nominal Animal
author_rank: Super Contributor
timestamp: October 01, 2025, 09:28:57 am
content: Quote from: daisizhou on September 30, 2025, 02:37:11 amForwardvoltage, actually: a pair of 2.7V forward voltage LEDs in series is 5.4V total.I cannot find any white LEDs in 0603 that have notable light output at 2.48V forward voltage, though. If you do have such (easily verified!), then I don't see why it wouldn't work.What you could do, however, is modify the PCB, by cutting the trace between each series pair, and adding two jumper wires to put all 96 LEDs in parallel. That would be a 192 tiny little jumper wires on that PCB, however... You did say soldering is not an issue!Another option is to use just half the number of LEDs, shorting and not using one of each series pair, using very diffuse and wide-angle LEDs. Consider a checkerboard pattern to avoid the light striping, like looking through window blinders.If you desolder all the old LEDs first, you can always experiment with a cluster near the center of the display first, before soldering all the LEDs in place.