From Trash To TV

In days gone by, when TVs had CRTs and still came in wooden cabinets, a dead TV in a dumpster was a common sight. Consumer grade electronic devices of the 1960s and ’70s were not entirely reliable, and the inside of a domestic TV set was not the place for them to be put under least stress. If you were electronic-savvy you could either harvest these sets as a source of free components, or with relative ease fix them for a free TV set.

With today’s LCDs, integrated electronics, and electronic waste regulations, the days of free electronics in every dumpster are largely behind us. Modern TVs are more reliable, and when they reach end-of-life we’re less likely to see them.

[Sidsingh] happened to find an LCD TV in a dumpster, and being curious as to whether he could fix it or salvage some components, cracked it open to take a look.

He found that somebody had already been into the set and that some components on the PSU and backlight boards showed evidence of magic smoke escaping, having been desoldered by the previous repairer. The signal board was intact though, a generic Chinese model based around a Mediatek MTK8227 SoC. Information was scarce on these boards, but some patient research yielded a schematic for a similar set.

Once he knew more about the circuit, he was able to identify the power lines and discovered that the 1.8v line to the SoC was faulty. This he traced to a switching regulator for which there was no equivalent in his junkbox, so he substituted a linear regulator to obtain the required voltage. The CFL backlight was then removed and replaced with LED strips, and as if by magic he had a working TV set.

This might seem a relatively mundane achievement on the scale of some of the projects we feature on these pages, but it is an important one. In these days of throwaway items it is still not impossible to repair dead electronic devices, indeed as [Sidsingh] found the power supply is most likely to be the culprit. If you score a dead LCD TV then don’t be afraid to crack it open yourself, you may be able to fix it.

As you might imagine, many repairs have made it onto Hackaday over the years. Of relevance to this one is this LCD that inexplicably worked when exposed to light, an LED backlight conversion, and this capacitor swap to return an LCD monitor to health.

Repairing and Improving Cheap Bench Power Supplies

Cheap benchtop power supplies are generally regarded as pieces of junk around these parts. They can measure well enough under perfect conditions, but when you use them a little bit, they fall over. There’s proof of this in hundreds of EEVblog posts, Amazon reviews, and stories from people who have actually owned these el-cheapo power supplies.

One of the guys who has had a difficult time with these power supplies is [Richard]. He picked up a MPJA 9616PS (or Circuit Specialists CSI3003SM) for a song. It quickly broke, and that means it’s time for a repair video. [Richard] is doing this one better – he has the 3A power supply, that sells for $55. With a stupidly simple modification, he upgraded this power supply to the 5A model that usually sells for $100.

The problem with [Richard]’s broken power supply were voltage and current adjustments knobs. This cheap power supply didn’t use rotary encoders – voltage and current were controlled by a pair of 1k and 10k pots. Replacing these parts cost about $5, and [Richard]’s power supply was back up on its feet.

After poking around inside this power supply, [Richard] noticed two blue trim pots. These trim pots were cranked all the way to the left, and by cranking them all the way to the right, the power supply could output 5 Amps. Yes, the 3A version of this power supply was almost identical to the 5A version, with the only difference being the price. It’s a good repair to a somewhat crappy but serviceable supply, but a great mod that puts a beefier power supply on [Richard]’s desk.

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Fixing Broken Monitors By Shining A Flashlight

[dyril] over on the EEVblog has a broken LED TV. It’s a fairly standard Samsung TV from 2012 that unfortunately had a little bit of corrosion on the flexible circuit boards thanks to excessive humidity. One day, [dyril] turned on his TV and found about one-third of the screen was glitchy. After [dyril] took the TV apart, an extremely strange fix was found: shining a light on the corroded flexible circuit board fixed the TV.

The fix, obviously, was to solder a USB light to a power rail on the TV and hot glue the light so it shines on the offending circuit. Solving a problem is one thing, though, understanding why you’ve solved the problem is another thing entirely. [dyril] has no idea why this fix works, and it’s doubtful anyone can give him a complete explanation.

The TV is fixed, and although you can’t argue with results, there is a burning question: how on Earth does shining a light on a broken circuit board fix a TV? Speculation on the EEVblog thread seems to have settled on something similar to the photonic reset of the Raspberry Pi 2. In the Raspberry Pi 2, a small chip scale package (CSP) used in the power supply section would fail when exposed to light. This reset the Pi, and turned out to be a very educational introduction to photons and energy levels for thousands of people with a Pi.

The best guess from the EEVblog is that a chip on the offending board handles a differential signal going to the flex circuit. This chip is sensitive to light, and shutting it down with photons allows the other half of the differential signal to take over. It’s a hand-wavy explanation, but then again this is a very, very weird problem.

You can check out [dyril]’s video demonstration of the problem and solution below. Thanks [Rasz] for sending this one in.

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Nikon Resurrection: Repairing a Broken Lens

Modern DSLR cameras are amazing devices. Mechanics, electronics, and optics, all rolled up in a single package. All that technology is great, but it can make for a frustrating experience when attempting any sort of repair. Lenses can be especially difficult to work on. One misalignment of a lens group or element can lead to a fuzzy image.

[Kratz] knew all this, but it didn’t stop him from looking for a cheap lens deal over on eBay. He found a broken Nikon DSLR 55-200mm 1:4-5.6 AF-S VR camera lens for $30. This particular lens is relatively cheap – you can pick up a new one for around $150 online. Spending $30 to save $120 is a bit of a gamble, but [Kratz] went for it.

The lens he bought mostly worked – the auto-focus and vibration reduction system seemed to be fine. The aperture blades however, were stuck closed. Aperture blades form the iris of a lens. With the blades closed down, the lens was severely limited to brightly lit situations. All was not lost though, as the aperture is a relatively simple mechanical system, which hopefully would be easy to repair.

pinNikonKeeping screws and various parts in order is key when taking apart a lens. [Kratz] used a tip he learned right here on Hackaday: He drew a diagram of the screw positions on a thick piece of paper. He then stuck each screw right into the paper in its proper position.

Carefully removing each part, [Kratz] found a pin had slipped out of the rod that connects the lens’ internal parts with the external aperture control arm. Fixing the pin was simple. Getting the lens back together was quite a bit harder. Several parts have to be aligned blindly. [Kratz] persevered and eventually everything slipped into alignment. The finished lens works fine, albeit for a slightly noisy auto-focus.

It’s worth noting that there are service and repair manuals for many cameras and lenses out there in the dark corners of the internet, including [Kratz]’s 55-200 lens. Reading the repair procedures Nikon techs use shows just how many tools, fixtures, and custom bits of software go into making one of these lenses work.

Electrolytic Capacitor Repair

If you’ve ever worked on old gear, you probably know that electrolytic capacitors are prone to failure. [Dexter] undertook a repair of some four-decade-old capacitors in a power supply. He didn’t replace them. He fixed the actual capacitors.

The reason these units are prone to fail is the flip side of what people like about electrolytics: high capacitance in a small package. In a classic parallel plate capacitor, the capacity goes up as the distance between the plates shrinks. In an electrolytic, one plate is a rolled up spiral. The other plate is conductive fluid. The insulator between (the dielectric) is a very thin layer of oxide that forms on the spiral. Over time, the oxide degrades, but this degradation repairs itself when using the capacitor. If the capacitor isn’t powered up for an extended period, the oxide will degrade beyond the point of self-repair.

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Flashed the wrong firmware? Swap out the LCD to match!

We always joke about the hardware guys saying that they’ll fix it in firmware, and vice-versa, but this is ridiculous. When [Igor] tried to update his oscilloscope and flashed the wrong firmware version in by mistake, he didn’t fix it in firmware. Instead, he upgraded the LCD display to match the firmware.

See, Siglent doesn’t make [Igor]’s DSO any more; they stopped using the 4:3 aspect ratio screens and replaced them with wider versions. Of course, this is an improvement for anyone buying a new scope, but not if you’ve got the small screen in yours and can’t see anything anymore. After playing around with flashing other company’s firmware (for a similar scope) and failing to get it done over the JTAG, he gave up on the firmware and started looking for a hardware solution.

It turns out that a few SMT resistors set the output screen resolution. After desoldering the appropriate resistors, [Igor] bought a new 7″ LCD screen online only to find out that it has a high-voltage backlight and that he’d need to build an inverter (and hide the noisy circuit inside his oscilloscope). Not daunted, he went digging through his junk box until he found a backlight panel of the right size from another display.

Yet more small soldering, and he had frankensteined a new backlight into place. Of course, the larger LCD won’t fit the case without some cutting, double-sided tape, and a healthy dose of black tape all around insulates the loose electricals. Et voilá!

We have to hand it to [Igor], he’s got moxie. It’s an ugly hack, but it’s a definite screen upgrade, and a lesser hacker would have stopped after flashing the wrong firmware and thrown the thing in the trash. We’d be proud to have that scope sitting on our desk; it’s a definite conversation starter, and a badge of courage to boot.

Macintosh Hard Drive Repair

The Macintosh II was a popular computer in the era before Apple dominated the coffee shop user market, but for those of us still using our Mac II’s you may find that your SCSI hard drive isn’t performing the way that it should. Since this computer is somewhat of a relic and information on them is scarce, [TheKhakinator] posted his own hard drive repair procedure for these classic computers.

The root of the problem is that the Quantum SCSI hard drives that came with these computers use a rubber-style bump stop for the head, which becomes “gloopy” after some time. These computers are in the range of 28 years old, so “some time” is relative. The fix involves removing the magnets in the hard drive, which in [TheKhakinator]’s case was difficult because of an uncooperative screw, and removing the rubber bump stops. In this video, they were replaced with PVC, but [TheKhakinator] is open to suggestions if anyone knows of a better material choice.

This video is very informative and, if you’ve never seen the inside of a hard drive, is a pretty good instructional video about the internals. If you own one of these machines and are having the same problems, hopefully you can get your System 6 computer up and running now! Once you do, be sure to head over to the retro page and let us know how you did!

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