[Mr. Carlson] Fixes A Fridge

September 21, 2019 by Dan Maloney 28 Comments

A dead refrigerator is an occurrence determined to frustrate any homeowner. First there’s the discovery of hundreds of dollars in spoiled food, and then the cost of a repair call and the delay of the inevitable wait for parts. It’s clear to see why a hacker like [Mr. Carlson] would seek another way.

Now, normally a fridge repair video would by unlikely fodder for a Hackaday article. After all, there’s generally not much to a fridge, and even with the newer microprocessor-controlled units, diagnosis and repair are usually at the board-level. But [Mr. Carlson] has had this fridge since 2007, and he’s got some history with it. An earlier failure was caused by the incandescent interior lights welding relay contacts closed thanks to huge inrush currents when starting the cold filaments. That left the light on all the time, heating the interior. His fix was a custom solid-state relay using zero-crossing opto-isolators to turn the bulbs on or off only when the AC power was at a minimum.

That repair kept things going for years, but when the latest issue occurred, [Mr. Carlson] took a different tack. He assumed that a board that has been powered 24-7 for the last twelve years is likely to have a bad capacitor or two. He replaced all the caps, threw in a few new relays to be on the safe side, and powered the fridge back up. It whirred back to life, ready for another decade or so of service.

Kudos to [Mr. Carlson] for his great repair tips and his refusal to surrender. The same thing happened when his solder sucker started to give up the ghost and he fixed it by adding a variable-frequency drive.

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Eagle Reborn: F-15 Simulator From A Wreck

September 4, 2019 by Maya Posch 37 Comments

This story started all the way back in September 12, 1981, when an F-15C aircraft’s landing attempt at Soesterberg Airbase during an airshow went completely FUBAR and the airframe was scrapped. The forward fuselage section was sold and eventually ended up with [Gene Buckle] who began work on creating a fully accurate F-15C simulator using these parts. He has blogged about his progress since 2009 over at the project website.

The F-15C was number 80-0007, which at the time of the crash had flown only 9.5 hours total, making it a very early retirement for an incredible fighter jet. But now the Eagle is back, or at least part of it: [Gene] managed to get the whole system into a state where the instrumentation and controls work again, using the original computer systems and instruments where they were still usable. You can find the YouTube video embedded after the break as well.

Detailed technical information on the F-15 series and this simulator build can be found on the project site, which is awesome both for F-15 fans and those who are into really accurate simulators.

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Odd-Sized Military Headphone Connectors, Tamed!

August 31, 2019 by Jenny List 21 Comments

Military headphones, at least the older ones, are like few other sound reproducers. They are an expression of function over form, with an emphasis on robustness over operator comfort. Electrically they most often have high-impedance drivers and annoyingly proprietary connectors for whichever obscure radio system they were a part of.

[John Floren] has a HS-16A headset, the type used by the US military during the Vietnam war. It’s an antiquated design with a dual spring steel headband and on-the-ear ‘phones with no muff for comfort, and a quick bit of research finds that they can be had brand new in their 1960s packaging for somewhere around $20. Their connector is a pair of odd metal pins, and rather than doing what most of us would do and snipping the wire to fit something more useful, he hunted high and low for a TE Connectivity receptacle that would fit them. A short extension and a jack plug allowed him to use these slightly unusual cans.

This isn’t a special hack, but it’s still an interesting read because it sheds a bit of light upon these old-style headphones and reveals that they’re still available for anyone who wants their radio operating to have a retro feel. If you buy a set, you’ll probably still have them decades after more modern pairs have bitten the dust.

Expensive Sony Lens Repair Reveals Shims & Shifts

August 6, 2019 by Richard Baguley 5 Comments

The photographic hire company Lensrentals had a $2k Sony FE 135mm f1.8 GM camera lens returned with a problem: it was having issues focusing. So, they decided to do the obvious thing and take it apart. It’s a fascinating insight into some of the engineering that goes into a high-end camera lens.

That is perhaps a rather scary thing to do, because this is a very new lens that doesn’t even have a service manual yet. That’s akin to rechipping a Ferrari when you’ve never even opened the hood before.

One of the interesting things inside is the presence of a number of shims that adjust the placement between the groups of lens elements. It seems that however good their manufacturing tolerances are, sometimes you just have to put a shim or two in there to align things.

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Liquid Damaged MacBook Saved With A Keen Eye

July 9, 2019 by Tom Nardi 20 Comments

Even among those of us with a penchant for repairing electronics, there are some failures which are generally considered too severe to come back from. A good example is liquid damage in a laptop; with so many components and complex circuits crammed into such a small area, making heads or tails of it once the corrosion sets in can be a real nightmare. Especially in the case of an older laptop, the conventional wisdom is to try and recover your files and then buy a new one.

But as we’ve come to learn, [Jason Gin] is not a man who often finds himself concerned with conventional wisdom. After finding an older MacBook with suspected liquid damage, he decided to see what it would take to restore it to working order. According to a note on the device, the screen was dead, the USB ports were fried, the battery didn’t take a charge, and it wouldn’t boot. No problem then, should be easy.

Upon opening up the circa-2012 laptop, [Jason] found the machine to be riddled with corrosion. We’re not just talking surface gunk either. After giving everything a good cleaning with isopropyl alcohol, the true extent of the damage became clear. Not only had traces on the PCB rotted away, but there were many components that were either damaged or missing altogether. Whatever spilled inside this poor Mac was clearly some nasty stuff.

[Jason] used OpenBoardView to pull up schematics and diagrams of the motherboard, and started the arduous task of visually comparing them to his damaged unit. In some areas, the corrosion was so bad he still had trouble locating the correct traces and pads. But with time and effort, he was able to start probing around and seeing what components had actually given up the ghost.

For the USB ports it ended up being a bad 10-microfarad ceramic capacitor, but for the LCD, he ended up having to replace the entire backlight driver IC. The prospect of working on this tiny BGA-25 device might have been enough for some to throw in the towel, but compared to the hand-soldered magnet wire repairs required elsewhere on the board, [Jason] says the installation of the new LP8550 chip was one of the easier aspects of the whole operation.

The write-up is a great read if you like a good repair success story, and we especially like the way he documented his diagnosis and resulting work on a per-system basis. It makes it much easier to understand just how many individual fires [Jason] had to put out. But if you’re more interested in feats of steady-handed soldering, check out his recent project to add a PCI-E slot to the Atomic Pi.

Lighting Tech Dives Into The Guts Of Laser Galvanometers

June 29, 2019 by Dan Maloney 12 Comments

There’s something magical about a laser light show. Watching that intense beam of light flit back and forth to make shapes and patterns, some of them even animated, is pretty neat. It leaves those of us with a technical bent wondering just exactly how the beam is manipulated that fast.

Wonder no more as [Zenodilodon], a working concert laser tech with a deep junk bin, dives into the innards of closed-loop galvanometers, which lie at the heart of laser light shows. Galvos are closely related to moving-coil analog meters, which use the magnetic field of a coil to deflect a needle against spring force to measure current. Laser galvos, on the other hand, are optimized to move a lightweight mirror back and forth, by tiny amounts but very rapidly, to achieve the deflection needed to trace out shapes.

As [Zeno] explains in his teardown of some galvos that have seen better days, this means using a very low-mass permanent magnet armature surrounded by coils. The armature is connected to the mirror on one end, and a sensor on the other to provide positional feedback. We found this part fascinating; it hadn’t occurred to us that laser galvos would benefit from closed-loop control. And the fact that a tiny wiggling vane can modulate light from an IR LED enough to generate a control signal is pretty cool too.

The video below may be a bit long, but it’s an interesting glimpse into the day-to-day life of a lighting tech. It puts a little perspective on some of the laser projection projects we’ve seen, like this giant Asteroids game.

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Home Made Gears Save This Shredder

June 23, 2019 by Jenny List 16 Comments

It’s very likely that a majority of readers will have had a gear fail in a piece of equipment, causing it to be unrepairable. This is a problem particularly with plastic gears, which shed teeth faster than a child who has discovered the financial returns of the Tooth Fairy.

[BcastLar] has a shredder with a gear that has, well, shredded. He’s posted a video series over three parts that while ostensibly about fixing his shredder, is in reality a three-part tutorial on how to create custom gears using FreeCAD. While the principles of a gear are readily apparent to most observers their intricacies hide significant complexity which he does a great job of explaining. How to measure the parameters of a given gear, explaining mysteries such as pitch angle or beta, he breaks everything down in easy to understand steps.

His tool of choice is FreeCAD, and while he explains that FreeCAD has the ability to make gears from scratch the tool employed in the videos is the Gear Workbench plugin. He shows how this software removes the complexity of creating a gear, and shows the process on his screen as he creates the custom shredder part.

Finally, the process of 3D printing the gear is explained. You might ask why not machine it, to which he responds that tooling for non-standard gear profiles is prohibitively expensive. We’ve placed all three videos below the break, and we think you might want to make yourself a cup of tea or something and work through them.

Thanks [Andy Pugh] for the tip.

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