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I'm currently on rev 3 of my ThinkPad-specific LED retrofit driver boards. They fit into the space on a stock inverter freed up by removing the CCFL step-up coil.

I'm on pace to make about 200-300 kits this year, and I'm still making them all by hand. Solder paste applied using a pneumatic dropper, components placed using tweezers and stereo microscope, then reflowed using a hotplate (thus the little placement jigs with silicone handles).

more after the cut... )

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LEDs and LED strip PCBs are finally here!

So now it's time to catch up with the LED backlight kit orders, aka, I know where all my free time is going the next few weeks...

(Does anyone else still remember the Dunkin' "Time to make the donuts" commercials?)

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First, the big if belated news: I'm now selling complete kits for T-series machines from the T20 through T500, as well as the W500. Oh, and let's not forget the T70. I do need to update the kits webpage to reflect all the new models.

This adds to the X-series kits I already offer for the X20 through the CCFL versions of the X200. And yes, the X62 as well.

That said, I'm waiting on an order of LEDs from Nichia. My most recent order collided badly with the beginning of Golden Week, so the arrival ETA is around May 30th. I won't be able to build new kits until then, and the buyers queue is currently about a week deep.

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Since I love LEDs and I love meters, it is totally obvious to put LEDs into meters.

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spoiler: Nichia Rocks. But first a flashback.

Remember those crazy Chinese LEDs I was looking for? They had kind of iffy construction, but up to that point they were the closest color match I could find to what I needed for my Thinkpad backlight project. I found more of the same type from random Chinese resellers, but none with exacly the same whitepoint as the original. I never determined the manufacturer.

I was looking for these dodgy Chinese LEDs because I couldn't get any major manufacturers or resellers to sell me the LEDs I needed in any kind of reasonable quantity. The smallest amount any factory quoted was a MOQ of 100,000 and that was only because a friend of a friend was willing to call in a favor to an unnamed factory in Hebei. The name brands you'd recognize weren't willing to discuss anything less than 1,000,000 units.

Or so I thought. I'd stopped looking slightly too early.

The AFFS LCDs I'm retrofitting have red and green filters with a lot of overlap in the yellow region because the original CCFL backlight doesn't put out much yellow. The broad yellow peak from typical white LEDs pollutes the red and green primaries. That messes up the saturation and color reproduction, even if the white point is correct.

But last year Nichia released a new line of component phosphor LEDs specifically designed for backlighting that don't use a broad yellow phosphor; they use separate red and green phosphors.

The specs also claimed tight binning, surprisingly high lumens/watt, and a weirdly low forward voltage. Oh, and they came in a low-profile 3014 package rated for mid-power output.

With no great optimism, I called up Nichia USA and asked for some samples. After being redirected a few times, I talked to a nice lady in Detroit who was happy to send me some LEDs for testing. That was farther than I expected to get.

The LED samples were everything the specs claimed them to be. I had never tested an LED as efficient, or with color binning so tight. They blew everything else out of the water.

So I called back. "What was the minimum order?" The answer: 1 reel, only 5,000 LEDs. Too good to be true.

The next question I was sure would undo me: "Can you tell me if I order now, what kind of bin I'll get?" I was still expecting to get something in the rough ballpark of what I really wanted that I could then tweak a bit with a filter. The reply: "What do you mean? You can have any bin mentioned on the spec sheet."

I could select specific whitepoint, forward voltage, and luminosity bin. At only 5,000 quantity. Jaw on floor.

It still felt too good to be true, but Nichia made the LEDs on-demand in Japan when I placed the order, and they arrived in the mail 15 calendar days later.

So as it turns out, I was able to get my dream LED for this silly little custom project. I'm reminded to post this now as there's been steady demand for the resulting Thinkpad backlight retrofit kits, and it's time to order another reel.

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There are so many posts that need to come out of this one...

I ordered a whole bunch of Chinese LED conversion kits. I tried lots of ways to mod them to work on Thinkpads, all of which worked... though many turn out not to work well enough, so don't use the mods on those pages for now :-(

Dissatisfied with all offerings, I designed and have been testing my own LED driver boards....

The LED strips that came with the Chinese kits all had terrible color rendering (low temperature, greenish, or both) on the spiffy AFFS screens the X61T is known for.

...so that's sucked me into the world of spectrometers, reverse engineering the protocols to use them on Linux (oh, yeah, I need to publish that), binning leds by hand with a makeshift integration chamber...

...and then of course all the software needed to take the SPD data from the assembled system and interpret the color data, then plot it, which I just finished today!

That contrast measurement is too low and I know why, the sensor is too close and unbaffled, so it's picking up IPS glow. Time for measurement jig rev 2....

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In case anyone was wondering what I was doing with all the LEDs recently, I've been converting classic Thinkpads with old, dying CCFL backlights to LED. It's a popular mod, and there are plenty of generic DIY backlight kits out there. Unfortunately, most of these kits don't work as-is, and there are no good instructions, walkthroughs, reviews or comparisons of various kits anyway.

I've just had a great deal of fun fixing that. Consider this a beta-test invitation :-)

Also... I touched the white tape. I touched it really quite a lot.

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I've been working on a backlight retrofit project with some odd and fairly tight spectral output requirements. Specifically, I need a cool-white LED with a very low CIE Y value. Something around x=.3 y=.28 resulting in a purplish/pinkish tinge.

As luck would have it, one of the first engineering samples I ordered from <insert random Chinese Supplier here> as part of a larger kit nailed the requirement perfectly. What luck! I ordered an additional large lot of exactly the same part--- and was sent completely different LEDs the second time around. The combination of language barrier and reluctance to name their own suppliers has meant I've made no progress on tracking more of these suckers down. I have 50. I need about 2000.

Large photomicrographs under the cut )


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