18th November 2018 18th November 2018 By Bzzz In project ccflccfl conversioncolor temperaturecrifujitsu p20-2high voltageledled strippolarizer

Fujitsu P20-2 CCFL to LED conversion (#P9)

Okay, so here’s something that I wanted to do for a long time, but it makes no sense in terms of time and money. But hey, I finally did it and it was fun!

I’ve shown my old Fujitsu P20-2 monitor previously as a comparison to the current 3440×1440 setup. It’s an old prosumer-grade 1600×1200 display, 20″, 60 Hz S-PVA panel with VGA and DVI inputs. Really good stuff. I got two of them after they failed by the dozen at university, where the tech guys even did a capacitor swap (these were in the upper three-digit Euro range when new, their replacements are totally overpriced 2560×1440 displays for 700€ a pop). Culprit however was more often a pair of MOSFETs, as they got pretty hot and that didn’t play well with the lead-free solder that was quite new at the time. So I got these two dead displays for free, which was pretty sweet.

One of them was in working condition, just the high voltage connectors were not applied correctly, which ended up in a shutdown of the HV generator and therefore no backlight. The second one actually had a more severe fault at the HV board, which is why I kept the entire unit, but in a non-working state. Not much hope for swapping in a different HV board, as this display uses 3 CCFLs each on top and bottom, which should be pretty rare. But as I have a working counterpart, troubleshooting the unit is pretty straight forward.

So after dismantling another failed (more recent) monitor on Saturday, I decided to finally work on the P20 once again – make it or break it. Time for an LED conversion!

Grab three different screwdrivers and rip out everything. Outer shell, back metal cover, metal case, several metal and plastic shells, and finally the top and bottom CCFL bars can be separated.

Carefully extract the CCFLs and put in a high density LED strip (3014 type?).

Put the bars back in, screw everything place. Now what about the three film layers? I had preserved the order when I removed them, but that didn’t make sense. So I made an educated guess and shoved them in in a different order (NOT shown the photo!). So the top layer has to be the polarizer, as other films above will probably kill the fixed polarization and therefore screw up the LCD doing its thing. I would have put the birefractive layer to the bottom, but then I noticed that the film is extremely smooth and kind of sucks to the plastic base, which creates roundish spots that are clearly visible all the way (similar to two glass plates with just the tiniest drop of water in between). So the bottom layer has to be the coarse white diffractor to separate base and birefractor. The polarizer is also not smooth enough to stick to any other layer. It can be easily distinguished from the others by adding another polarizer to it, like from those disposable 3D glasses from the cinemas.

Cable routing, easier than with the 6 thicker HV wires before. Don’t overdo the hot snot

Unfortunately I couldn’t find the original cable that was used in between power supply and display board. However, a VGA cable from a recently dismantled CRT had the same plug type (12 pin instead of the 9 pins required) and as I needed to re-order the cables anyway, I just threw in a new socket from one of the AliExpress shopping tours this summer. As I had a working monitor of this type, pin assignment is known – 2x 5V, 2x GND, 2x 12V and then there’s some optional stuff. First one is a LVTTL power-on signal (out only, no way to turn the display on by applying a voltage), second and third are unknown – one of them should be display brightness, as that is regulated by the HV board. Doesn’t matter much, the monitor does work without knowing their exact function.

The first wiring didn’t work out, as breadboard cables do deliver some power, but not enough. The LED strips require around 0.75 to 0.80 amps at 12V (dimmer on less voltage – no problem), and the VGA board needs only the tiniest amount of current @12V, but gulps about 2.8A on the 5V rail. And won’t start when below like 4V. That’s not going well even with just 10cm of breadboard cables.

So when voltages are up the display complains about missing inputs – here we go!

It’s alive! (and it has two specks of dust in it, grr)

Next steps, and here’s the financial nonsense part: Buy a dual power supply 230V AC -> 5V/12V DC (Mean Well RD50-A fits perfectly – around 15€) and exchange the 3000K “piss” yellow LED strips with something close to 6000K. I’ve ordered a meter of those strips with an advertised CRI of 82, ~15W per meter @ 200ish LEDs, already. That should do the trick for another 5€. So 20€ and a few hours for the CCFL to LED conversion of a monitor that is no longer in use…but I finally managed to do it, I can give away the second unit that’s also gathering dust in my wardrobe, and I had a ton of fun reviving this excellent piece of hardware. 8/10, would do that again!