repair

268 Articles

LCD Stackup Repair: Not For The Faint Of Heart

February 23, 2025 by 11 Comments

Coming straight to the point: [Ron Hinton] is significantly braver than we are. Or maybe he was just in a worse situation. His historic Acer K385s laptop suffered what we learned is called vinegar syndrome, which is a breakdown in the polarizers that make the LCD work. So he bit the bullet and decided to open up the LCD stack and replace what he could.

Nothing says “no user serviceable parts inside” quite like those foil-and-glue sealed packages, but that didn’t stop [Ron]. Razor blades, patience, and an eye ever watchful for the connectors that are seemingly everywhere, and absolutely critical, got the screen disassembled. Installation of the new polarizers was similarly fiddly.

In the end, it looks like the showstopper to getting a perfect result is that technology has moved on, and these older screens apparently used a phase correction layer between the polarizers, which might be difficult to source these days. (Anyone have more detail on that? We looked around and came up empty.)

This laptop may not be in the pantheon of holy-grail retrocomputers, but that’s exactly what makes it a good candidate for practicing such tricky repair work, and the result is a readable LCD screen on an otherwise broken old laptop, so that counts as a win in our book.

If you want to see an even more adventurous repair effort that ended in glorious failure, check out [Jan Mrázek]’s hack where he tries to convert a color LCD screen to monochrome, inclusive of scraping off the liquid crystals! You learn a lot by taking things apart, of course, but you learn even more by building it up from first principles. If you haven’t seen [Ben Krasnow]’s series on a completely DIY LCD screen, ITO-sputtering and all, then you’ve got some quality video time ahead of you.

Bicycle Adds Reliability With Second Chain

February 3, 2025 by 70 Comments

Ignoring the International Cycling Union‘s mostly arbitrary rules for what a bicycle is “supposed” to look like (at least if you want to race), there are actually reasons that the bicycling world has standardized around a few common parts and designs. Especially regarding the drivetrain, almost all bikes use a chain, a freewheel, and a derailleur if there are gears to shift because these parts are cheap, reliable, and easy to repair. But if you’re off grid in a place like Africa, even the most reliable bikes won’t quite cut it. That’s why a group called World Bicycle Relief designed and built the Buffalo bicycle, and the latest adds a second gear with a unique freewheel.

Bicycling YouTuber [Berm Peak] takes us through the design of this bike in his latest video which is also linked below. The original Buffalo bicycle was extremely rugged and durable, with a rear rack designed to carry up to 200 pounds and everything on the bike able to be repaired with little more than an adjustable wrench. The new freewheel adds a second gear to the bike which makes it easier to use it in hilly terrain, but rather than add a complicated and hard-to-repair derailleur the freewheel adds a second chain instead, and the rider can shift between the two gears by pedaling backwards slightly and then re-engaging the pedals.

Of course a few compromises had to be made here. While the new freewheel is nearly as rugged as the old one, it’s slightly more complex. However, they can be changed quite easily with simple tools and are small, affordable, and easy to ship as well. The bike also had to abandon the original coaster brake, but the new rim brakes are a style that are also easy to repair and also meant that the bike got a wheel upgrade as well. Bicycles like these are incredibly important in places where cars are rare or unaffordable, or where large infrastructure needed to support them is unreliable or nonexistent. We’ve seen other examples of bicycles like these being put to work in places like India as well.

Thanks to [Keith] for the tip!

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Repairing A BPS-305 30V Bench Power Supply

December 31, 2024 by 6 Comments

When [Tahmid Mahbub] recently reached for his ‘Lavolta’ BPS-305 bench supply, he was dismayed to find that despite it being a 30V, 5A-rated unit, the supply refused to output more than 15V. To be fair, he wasn’t sure that he had ever tried to push it beyond 15V in the years that he had owned it, but it had better live up to its specs. Ergo out came the screwdriver to open the power supply to see what had broken, and hopefully to fix it.

After some more probing around, he discovered that the unit had many more issues, including a highly unstable output voltage and output current measurement was completely wrong. Fortunately this bench power supply turns out to be very much like any number of similar 30V, 5A units, with repair videos and schematics available.

While [Tahmid] doesn’t detail his troubleshooting process, he does mention the culprits: two broken potentiometers (VR104 and VR102). VR104 is a 5 kOhm pot in the output voltage feedback circuit and VR102 (500 Ohm) sets the maximum output current. With no 500 Ohm pot at hand, a 5 kOhm one was combined with a 470 Ohm resistor to still allow for trimming. Also adjusted were the voltage and current trimpots for the front display as they were quite a bit off. Following some testing on the reassembled unit, this power supply is now back in service, for the cost of two potentiometers and a bit of time.

The Mystery Of The Messed-Up Hammond X5

December 24, 2024 by 4 Comments

[Filip] got his hands on a sweet old Hammond X5 organ, but it had one crucial problem: only half of the keys worked. Each and every C#, D, D#, E, F, and F# would not play, up and down the keyboard, although the other notes in between sounded just fine.

Those of you with an esoteric knowledge of older electric organs will be saying “it’s a busted top-octave generator chip”, and you’re right. One of the TOGs worked, and the other didn’t. [Filip] rolled his own top-octave generator with a Pico, in Python no less, and the old beauty roared to life once more.

But what is a top-octave generator, you may ask? For a brief period of time in the early 70s, there were organs that ran on square waves. Because a musical octave is a doubling or halving of frequency, you can create a pitch for every key on the organ if you simply create one octave’s worth of pitches, and divide them all down using something as simple as a binary counter IC. But nobody makes top-octave chips any more.

Back in 2018, [DC Darsen] wrote in asking us if we knew about any DIY top-octave designs, and we put out an Ask Hackaday to see if you all could make a top-octave generator out of a microcontroller. We got a super-optimized code hack in response, and that’s worth checking out in its own right, but we always had the nagging suspicion that a hardware solution was the best solution.

We love how [Filip]’s design leans heavily on the Pico’s programmable input/output hardware modules to get the job done with essentially zero CPU load, allowing him to write in Python and entirely bypassing the cycle-counting and assembly language trickery. The voltage shifters and the switchable jumpers to swap between different top-octave chip types are a nice touch as well. If you have an organ that needs a top-octave chip in 2024, this is the way we’d do it. (And it sounds fantastic.)

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Saving An Electron Microscope From The Trash

December 13, 2024 by 17 Comments

Who wouldn’t want to have a scanning electron microscope (SEM)? If you’re the person behind the ProjectsInFlight channel on YouTube, you certainly do. In a recent video it’s explained how he got his mittens on a late 1980s, early 1990s era JEOL JSM-5200 SEM that was going to be scrapped. This absolute unit of a system comes with everything that’s needed to do the imaging, processing and displaying on the small CRT. The only problem with it was that it was defective, deemed irreparable and hence the reason why it was headed to the scrap. Could it still be revived against all odds?

The JEOL JSM-5200 SEM after being revived and happily scanning away. (Credit: ProjectsInFlight, YouTube)

The good news was that the unit came with the manual and schematics, and it turns out there’s an online SEM community of enthusiasts who are more than happy to help each other out. One of these even had his own JSM-5200 which helped with comparing the two units when something wasn’t working. Being an SEM, the sample has to be placed in a high vacuum, which takes a diffusion vacuum pump, which itself requires a second vacuum pump, all of which requires voltages and electronics before even getting to the amplification circuitry.

Since the first problem was that this salvaged unit wasn’t turning on, it started with the power supply and a blown fuse. This led to a shorted transformer, bad DC-DC converters, a broken vacuum pump, expired rubber hoses and seals, and so on, much of which can be attributed simply to the age of the machine. Finding direct replacements was often simply impossible to very expensive, necessitating creative solutions along with significant TLC.

Although there are still some small issues with for example the CRT due to possibly bad capacitors, overall the SEM seems to be in working condition now, which is amazing for a unit that was going to be trashed.

Thanks to [Hans] for the tip.

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Close Shave For An Old Oscilloscope Saved With A Sticky Note

November 23, 2024 by 12 Comments

When you tear into an old piece of test equipment, you’re probably going to come up against some surprises. That’s especially true of high-precision gear like oscilloscopes from the time before ASICs and ADCs, which had to accomplish so much with discrete components and a lot of engineering ingenuity.

Unfortunately, though, those clever hacks that made everything work sometimes come back to bite you, as [Void Electronics] learned while bringing this classic Tektronix 466 scope back to life. A previous video revealed that the “Works fine, powers up” eBay listing for this scope wasn’t entirely accurate, as it was DOA. That ended up being a bad op-amp in the power supply, which was easily fixed. Once powered up, though, another, more insidious problem cropped up with the vertical attenuator, which failed with any setting divisible by two.

With this curious symptom in mind, [Void] got to work on the scope. Old analog Tek scopes like this use a bank of attenuator modules switched in and out of the signal path by a complex mechanical system of cams. It seemed like one of the modules, specifically the 4x attenuator, was the culprit. [Void] did the obvious first test and compared the module against the known good 4x module in the other channel of the dual-channel scope, but surprisingly, the module worked fine. That meant the problem had to be on the PCB that the module lives on. Close examination with the help of some magnification revealed the culprit — tin whiskers had formed, stretching out from a pad to chassis ground. The tiny metal threads were shorting the signal to ground whenever the 4x module was switched into the signal path. The solution? A quick flick with a sticky note to remove the whiskers!

This was a great fix and a fantastic lesson in looking past the obvious and being observant. It puts us in the mood for breaking out our old Tek scope and seeing what wonders — and challenges — it holds.

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Simple PCB Repairs Keep Old Vehicle Out Of The Crusher

October 24, 2024 by 21 Comments

For those of us devoted to keeping an older vehicle on the road, the struggle is real. We know that at some point, a part will go bad and we’ll learn that it’s no longer available from the dealer or in the aftermarket, at least at a reasonable cost. We might get lucky and find a replacement at the boneyard, but if not — well, it was nice knowing ya, faithful chariot.

It doesn’t have to be that way, though, at least if the wonky part is one of the many computer modules found in most cars made in the last few decades. Sometimes they can be repaired, as with this engine control module from a Ford F350 pickup. Admittedly, [jeffescortlx] got pretty lucky with this module, which with its trio of obviously defective electrolytics practically diagnosed itself. He also had the advantage of the module’s mid-90s technology, which still relied heavily on through-hole parts, making the repair easier.

Unfortunately, his luck stopped there, as the caps had released the schmoo and corroded quite a few traces on the PCB. Complicating the repair was the conformal coating on everything, a common problem on any electronics used in rough environments. It took a bit of probing and poking to locate all the open traces, which included a mystery trace far away from any of the leaky caps. Magnet wire was used to repair the damaged traces, the caps were replaced with new ones, and everything got a fresh coat of brush-on conformal coating.

Simple though they may be, we really enjoy these successful vehicle module repairs because they give us hope that when the day eventually comes, we’ll stand a chance of being able to perform some repair heroics. And it’s nice to know that something as simple as fixing a dead dashboard cluster can keep a car out of the crusher.

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