xiphmont

The holidays are over and I'm back to having a little hobby time here and there. With the LED mod assembled and in place, the coaxial illuminator is certainly much brighter than the original halogen-powered unit. Of course, an LED ring light still utterly destroys it, but the brightness level of the modded version is usable in a lit room, where the original halogen version really wasn't. So, yay.

However... contrast is damaged somewhat? Did I get some optics dirty?

A little investigation reveals our problem is at the primary constraint in the optical path. Specifically, the coaxial illuminator is designed to focus down an image of the light source right at the plane of the internal adjustable iris in order to get as much useful light through it as possible. You can see the glowing filament clearly when the iris is nearly closed, and it passes through cleanly with the iris open.

When the light doesn't clear the iris but shines on it instead, the light pollutes the image. Interestingly, this means the adjustable iris and coaxial illuminator don't really coexist well, a problem I hadn't noticed before but yup.... sure enough... the illuminator is only really useful with the iris wide open.

Possibly for this reason, the slightly later SZH10 dispenses with the adjustable iris for a fixed aperture, instead offering the iris as an accessory 'slice' that can be placed later in the optical path. This neatly avoids the contrast problem.

In any case, my problem is 90% a slight misalignment, easily dealt with.

That said, the square die image is just a bit too large to fit cleanly through the round iris opening even when aligned. A little optimization of my illuminator optics is probably called for.

But... can I actually do better? Olympus knew what they were doing, and if there was an obviously better lens design they'd have used it, right?

Stay tuned for our next exciting episode!

Electronics assembly!

But does it, for the lack of a better word, chooch?

Yes, it chooches.

Adding the pot to test the adjustment, it turns out my BuckBlock is sourcing more than 500uA-- it's actually closer to 625uA. Also, it's firing up at ~1.5v rather than ~ 1.75v. That means I want a 2.2k low-end resistor and a lower pot resistance. So I modded another 10k linear pot into a 13k exp-ish pot, and continued assembly.

Everything goes together as intended and looks nice.

But there's a snag; I knew there was a good chance the optics wouldn't play as well with the SZH as I hoped, and in fact, the focus behavior isn't working well once on the scope. The illuminator works, and alignment is spot-on, but it's focusing an image of the lens at working depth, which is suboptimal. Also due to the suboptimal focus, lots of light is getting wasted inside the scope as it scatters out of the parallel-light/infinity focus portion of the optical path.

I'm going to have to play more with it.

Earlier this year, when I was building mods for my Olympus SZH microscope, I planned a coaxial illuminator using LEDs. The design got... a little out of hand...

...and I put it aside.

Last week I stumbled upon noq2's blog, where he documented his LED mod for the same microscope. It's the polar opposite to what I was doing. His is simple, brute force, and gets the job done. Go have a read, it's nicely done (and his animated gifs of the SZH internals are great). And did I mention it's actually finished and working? :-)

This inspired me to reconsider what I was doing.

I mean, I know what I was thinking: a design worthy of the rest of the absurdly overbuilt Olympus. I mean, just look at the original collimator! They use front-surface mirrors in the light source!

Also I didn't want to sacrifice any original Olympus parts. Complete SZH coaxial illuminators still sell for over a grand. But that's mostly because they're usually missing accessories needed to operate them (the bulb holder and transformer) which I didn't need. Last summer I picked up a bare illuminator block for $90. That's cheap enough I'm willing to mod it permenently.

Then I saw noq2's build. It was brilliant. And even better, I can have everything I originally wanted with a dead-simple addition.

The whole 'tactical flashlight' craze has spawned a smorgasboard of cheap, canned collimation optics for LEDs. They're even better than lenses as they sit all around the emitter instead of a distance in front, so they catch more light. Most are 90%+ efficient.

So I'm taking what noq2 did and slapping a $2 spot-collimator on front. No muss, no fuss. Well, I have to fuss a bit, so I'll put the driver electronics inside the housing, and add an intensity adjustment too. Still not *much* fuss.

...beginning with hacking off a big ol' chunk of heatsink using a dull beaver...

and cleaning it up a bit on a sharper beaver.

Trim to fit the existing enclosure, with an eye toward reusing the existing mounting holes on the enclosure's rear boss. Also drill and tap holes for LED mounting, power jack, and a notch for a BuckBlock controller, and we end up with something like:

I want an intensity adjustment knob, so I stole the boss off the prototype I machined earlier this year. Along with bolts, a really nice 11-position-with-detents potentiometer, and the aforementioned LED optics (but not including wires) we finally end up with this exploded build:

Next up will be a little paint, a schematic, and build/test.

I've previously regaled you with stories of poorly rebuilt SXGA+ screens being sold as new that are the bane of X62 builders. Whelp, I'm beginning to think just about every in-demand LCD panel on AliExpress stands a good chance of being a barely serviceable, cobbled together pile of poo. Usually sold as "NEW" or "GENUINE" or "100% ORIGINAL" of course.

I'm building some T70s now, and the screens folks like to have in these are the IAQX10 2k 4:3 AFFS screens from the old IDTech joint venture. Like the SXGA screens for the X62, these are long out of production, still in demand, and hard to find in the wild. I've been working out how to mod the much thicker industrial -M version, which uses the same matrix, to work in a T70.

While I'm working that out, an IAQX10N seller pops up on AliExpress. The screens are expensive, but a genuine laptop version of this screen should be expensive at this point. I decided to buy just one so I had a comparison for my rebuild efforts.

Screen arrived, and lo and behold, it's a cobbled together pile of poo.

Immediately upon opening the box: the screen has a gloss front polarizer film. Uh oh. Stock is matte. Looking closer, it isn't even cut straight. Like, guys, at least use a straightedge.

Well, let's see if it at least works... and find it has a blank EDID. Uh huh. OK, let's get an IAQX10N EDID into it...

and we get:

The background on that screen? It's not supposed to be blue. It's supposed to be black. No, I didn't mess with the photo. 'Black' really looks like that. It's measuring less than 100:1 contrast; that blue is backlight bleed-through.

And the diagonal stripes? Not a trick of the picture. They're really there. It's Moiré patterning from using the wrong prism films for the given DPI, or not tacking them in-place and having them shift in transport.

This may well be the worst refurb job I've seen to date without being bent or cracked. Actually, I take it back, the outer frame is also slightly bent.

But hey! I'm only out $100 in shipping once I return it!

(In case you were wondering, the protective plastic film is still on the front of the screen in that picture, so all the bubbles and scratches are not real defects. But it does mean they did a lousy job putting the film on.)

The prototype boards are back from OSHPark. Dang, they did a really nice job.

Not perfect, but the cosmetic errors are mine; I submitted the protos to about 10 online PCB joints to see who'd actually make them to my DRC spec, and a few bits like silkscreen holdoff didn't actually match everywhere. I can adjust that for a real run.

OSHPark was one of two places willing to do 6mil/6mil 2oz without several rounds of human intervention. The other is DirtyPCBs, and I can't wait to see what comes back from there. Suffice to say I hope they're serviceable (as they're about 1/10th the cost in batches of 100), but it's highly unlikely they'll be as nice as this.

Maybe I can push the rest of the BOM to be able to afford the difference, I really like these...

I'm about to ship my 250th ThinkPad LED backlight kit, all hand-assembled and soldered. I had no idea. I expected there to be demand for about ten. The kits are for models over ten years old... and demand is still increasing.

Not pictured: The stack of 30 different headless ThinkPads I use for kit testing.

....w00t! Found the missing Thinkpad inverter stash! That should hold me through Christmas.

Another catch-up post.

A few weeks ago, I accepted my first order for a T43 backlight kit. It turned out to be a c-c-c-c-c-combo-breaker!

In the early days of software-controlled brightness, ThinkPads used an analog brightness signal like just about every notebook. It was generated by one of the D-to-A pins on the embedded Renesas H8S microntroller all ThinkPads used.

As of the X40, ThinkPads went to using a digital PWM brightness control generated by the Intel Centrino ICH Southbridge. This made them kind of weird by laptop standards. It's one of the reasons I had to cons up custom LED drivers for my ThinkPad brightness kits.

In general, the T and X series of the same generation shared a basic architecture. The planars were quite different, but the chipset and basic design were the same. Not so with the T4X and X4X.

The X40-series is a completely different design from the T40-series. It uses a PWM brightness control. The T40, however, is analog like the older machines, which threw me for a loop at first. The good news is that I'd made working drivers for the X2x, X3x, T2x and T3x beforehand, so once I realized the T4x was an 'old' style, getting it to work wasn't hard. I can use the same positive-analog TLD2 hack that worked on the earlier models.

The bad news is all my fabrication, based on the TLD3, is geared toward the PWM-based ThinkPads. The TLD3 boards aren't able to use a positive-analog brightness signal no matter the hack. For a TLD3, it's PWM input or nothing.

I have on hand ~ 1500 TLD3 PCBs, waiting to be populated, for the usual PWM kits. I have only ~ 20 TLD2 PCBs left that can be pressed into analog use.

Get 'em while you can.

The ThinkPad LED backlight kits consist of two major pieces; an LED strip and an LED driver. The driver boards are designed to fit onto existing CCFL inverter boards after removing the CCFL step-up coil.

For good measure, I pull off the CCFL driver chip as well. Simply disabling it doesn't keep it from drawing a [very small] amount of current.

Removing the driver chip also opens up additional possibilities for reusing traces on the existing PCB. I don't like running long wires across the width of the inverter when hooking up the LED driver board. They'd need to be glued down to avoid accidental snagging, and that's a complication I don't need.

Instead, I re-route power, ground and the ENA and DIM signals through the original board, using solder bridges and 0-ohm bridge resistors where possible. On most boards, one or two jumpers are still needed, though a few boards I can get away without using any.

This work is most definitely all done under the microscope.

That also reminds me-- I need to get my library of reference modification pictures up somewhere.

The LED strips are the big reason I still pick-and-place everything by hand. My tolerances here are just a few mils, and I've machined myself steel-and-aluminum templates to make the placement easier.

The idea is actually to place with looser tolerances, dropping the LEDs into the trough where the strip is clamped the check spacing and orientation with the microscope before reflow.

During reflow I tighten the guides on the jig and level the LEDs using a little precision squeegee I made out of aluminum and high-temp silicone.

Once the strip cools, I can pull it out of the jig, remove excess solder beads under the microscope, check for obvious defects, test on a power supply, and wash down with flux remover. Then it's on to applying the teflon layer, soldering pigtails, an up-to-temperature burn-in and flex test, and finally packaging.