I tried and failed to salvage the polarizer film of a Chunghwa CLAA133UA01 display panel, but that wasn’t the primary objective anyway. I turned to the real goal of salvaging its LED backlight and the first step is to remove the perimeter protective film. Most of my prior salvaged panels were held together with thin black plastic tape, this panel is slightly different in its use of shiny metallic foil tape. I was surprised to see it, as I thought foil would short-circuit the components underneath. Perhaps it is some sort of metallized plastic instead of metal foil. This stuff rips more easily than others but at least its adhesive still came off cleanly.

Once the foil was removed, I could see three important-looking chips on the circuit board.

Closest to the cable connector is a chip marked MST7337F-A AQ2T842B 1049B. A web search found Kynix Semiconductor MST7337 which is a chip for NTSC/PAL/SECAM automotive TV applications. I don’t think this is the right chip, but the correct answer eludes me. I might have better luck if I knew the logo, which is distinctive but not one I recognize. I didn’t see that logo on the Kynix Semiconductor page.

The next chip was marked AAT11771 A2U274 1052. A web search found a hit: Advanced Analog Technology AAT11771 is a controller for driving TFT LCD displays.

The third important-looking chip was marked A706B A38T 66040. Its proximity to the LED backlight connector makes it a prime candidate for the LED driver, it’s even next to the inductor + capacitor pairing consistent with a boost converter to raise voltage high enough to drive strings of LEDs. A search for A706B found that A706 is a standardized grade of steel bars for concrete reinforcement, but I saw nothing about a LED driver chip.

Pulling up the backlight connector for a look, I can see there are five thin conductors, one per contact point plus one thick conductor using three contact points. Remaining contact points between them are apparently unused. Based on what I’ve seen on other panels, I guessed the thick conductor is a common source for five current sinks for five parallel strings of LEDs.

This hypothesis was quickly and easily tested with a LED tester, so if I never manage to find information on that LED driver chip I should at least be able to drive these strings directly via copious test points visible in that area of the circuit board.

Until I find need for another diffused LED light source, this is a good stopping point. I put the LED backlight back into storage and pulled a non-dead panel out of my hardware archives. This one is still attached to a nominally working HP Stream 7 tablet.

After verifying I could illuminate LED strings of a LG LPP133WH2(TL)(M2) salvaged from a Dell laptop, I set it aside to work on the final panel in my stack of LCD laptop panels. This was salvaged from a Sony VAIO laptop whose model number I no longer know.

The original owner had spilled some cola on it. Good news: the spill did not immediately kill the machine so data could be pulled off averting any loss of data. Bad news: the computer started failing intermittently in strange ways as corrosion took hold, and eventually died a few weeks after the initial spill.

Removing the panel I see a label with designation Chunghwa CLAA133UA01. (Along with some dried coke residue.) Web lookup indicated this is a LED-backlit panel with 1600×900 resolution. Better than the 1366×768 resolution we see on baseline laptops today, but still short of full 1920×1080 resolution. Like the rest of my stack of panels, I decided it was not interesting enough to revive as a display.

My first task was removing the polarizer film in the front of the display, something I have yet to perfect through several past experiments. So far I’ve been able to remove the film in one piece but failed to clean off adhesive residue. For this panel, I didn’t even get that far. This panel used glue that was very strong, apparently stronger than the tensile strength of the polarizer film! Roughly a quarter of the way through peeling, the film tore apart and I decided to abandon polarizer retrieval.

Looking at the tear was mildly interesting. It was a zig-zag pattern instead of a straight line. This material is weakest at plus or minus 45 degrees relative to screen viewing orientation. Does that have any relation to polarization angle, or is it indicative of something else? I don’t have any tools to probe that question so I will set it aside for now and move on to the LED backlight.