Fixing A Busted Fluke While Fighting A Wonky Schematic

August 9, 2024 by Dan Maloney 16 Comments

Fluke meters have been around for a long, long time. Heck, we’ve got a Fluke 73 that we bought back in 1985 that’s still a daily driver. But just because they’ve been making them forever doesn’t mean they last forever, and getting a secondhand meter back in the game can be a challenge. That’s what [TheHWCave] learned with his revival of a wonky eBay Fluke 25, an effort that holds lessons for anyone in the used Fluke market.

Initial inspection of the meter showed encouragingly few signs of abuse, somewhat remarkable for something built for the military in the early 1980s. A working display allowed a few simple diagnostics revealing that the ammeter functions seemed to work, but not the voltmeter and ohmmeter functions. [TheHWCave]’s teardown revealed a solidly constructed unit with no obvious signs of damage or blown fuses. Thankfully, a service schematic was available online, albeit one with a frustrating lack of detail, confusing test point nomenclature, and contradictory component values.

Despite these hurdles, [TheHWCave] was able to locate the culprit: a bad fusible power resistor. Finding a direct replacement wasn’t easy given the vagaries of the schematic and the age of the instrument, but he managed to track down a close substitute cheap enough to buy in bulk. He searched through 40 units to find the one closest to the listed specs, which got the meter going again. Fixing the bent pin also gave the meter back its continuity beeper, always a mixed blessing.

If you’re in the market for a meter but can’t afford the Fluke name, picking up a busted meter and fixing it up like this might be one way to go. But are they really worth the premium? Well, kinda yes.

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A Soviet Cassette Recorder Receiving Some Love

July 29, 2024 by Jenny List 40 Comments

For those of us who lived in the capitalist west during the Cold War, there remains a fascination to this day about the Other Side. The propaganda we were fed as kids matched theirs in describing the awful things on the other side of the wall, something that wasn’t borne out when a decade or so later in the 1990s we met people from the former communist side and found them unsurprisingly to be just like us. It’s thus still of interest to have a little peek into Eastern Bloc consumer electronics, something we have the chance of courtesy of [DiodeGoneWild], who’s fixing a 1980s Soviet cassette recorder.

The model in question is a Vesna 309, and it has some audio issues and doesn’t turn the tape. It gets a teardown, the motor is cleaned up inside, and a few capacitor and pot cleanups later it’s working again. But the interest lies as much in the machine itself as it does in the repair, as it’s instructive to compare with a Western machine of the same period.

We’re told it would have been an extremely expensive purchase for a Soviet citizen, and in some ways such as the adjustable level control it’s better-specified than many of our equivalents. It’s based upon up-to-date components for its era, but the surprise comes in how comparatively well engineered it is. A Western cassette deck mechanism would have been a much more sketchy affair than the substantial Soviet one, and its motor would have been a DC part with a simple analogue speed controller rather than the brushless 3-phase unit in the Vesna. Either we’re looking at the cassette deck for senior comrades only, or the propaganda was wrong — at least about their cassette decks. The full video is below, and if you’re hungry for more it’s not the first time we’ve peered into electronics from the eastern side of the Iron Curtain.

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Vintage Ribbon Cable Repair Saves Poqet PC

July 26, 2024 by Jenny List 19 Comments

It sometimes seems as though computing power in your pocket is a relatively new phenomenon, but in fact there have been ultraportable computers since the 8-bit era. They started to become useful around the end of the 1980s though as enterprising manufacturers started cramming full-fat PC XTs into pocket form factors. Of these the one to own was the Poqet PC, a slim clamshell design that would run for ages on a pair of AA cells . If you have one today you’d be lucky if its display ribbon cable is without faults though, and [Robert’s Retro] is here with a fix previously thought impossible.

A large proportion of the video below the break is devoted to dismantling the unit, no easy task. The cable once exposed is found to have delaminated completely, and he takes us through the delicate task of attaching a modern equivalent. We particularly like the way in which the cable’s own springiness is used to retract it. The result has a white cable rather than the original black, but that’s a small price to pay for a machine that works rather than a broken paperweight.

If early pocket computing is your thing, it’s a subject we’ve covered before.

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Hack All The Things, Get All The Schematics

July 8, 2024 by Arya Voronova 31 Comments

When I was growing up, about 4 or 5 years old, I had an unorthodox favourite type of reading material: service manuals for my dad’s audio equipment. This got to the point that I kept asking my parents for more service manuals, and it became a running joke in our family for a bit. Since then, I’ve spent time repairing tech and laptops in particular as a way of earning money, hanging out at a flea market in the tech section, then spending tons of time at our hackerspace. Nowadays, I’m active in online hacker groups, and I have built series of projects closely interlinked with modern-day consumer-facing tech.

Twenty three years later, is it a wonder I have a soft spot in my heart for schematics? You might not realize this if you’re only upcoming in the hardware hacking scene, but device schematics, whichever way you get them, are a goldmine of information you can use to supercharge your projects, whether you’re hacking on the schematic-ed device itself or not. What’s funny is, not every company wants their schematics to be published, but it’s ultimately helpful for the company in question, anyway.

If you think it’s just about repair – it’s that, sure, but there’s also a number of other things you might’ve never imagined you can do. Still, repair is the most popular one.
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How To Find Replacement Parts When Model Numbers Don’t Match

May 22, 2024 by Donald Papp 24 Comments

[Sharad Shankar] repaired a broken TV by swapping out the cracked and malfunctioning image panel for a new one. Now, part-swapping is a great way to repair highly integrated modern electronics like televisions, but the real value here is something else. He documented his fix but the real useful part is his observations and guidance on how to effectively look for donor devices when the actual model of donor device can’t be found.

The usual approach to fixing a device by part swapping is to get one’s hands on two exact same models that are broken in different ways. But when it comes to consumer electronics with high turnovers — like televisions — it can be very difficult to actually locate any particular model once it’s no longer on shelves. [Sharad Shankar]’s broken TV was a 65″ TCL R646 purchased in 2021, and searching for a second 65″ TCL R646 was frankly like looking for a needle in a haystack. That’s when he got a visit from the good ideas fairy. Continue reading “How To Find Replacement Parts When Model Numbers Don’t Match” →

Ribbon Cable Repair Saves Touch ID

May 21, 2024 by Lewin Day 14 Comments

Some might consider a broken ribbon cable to be unsalvagable. They’re delicate and fragile as can be, and sometimes just fussing with them further is enough to cause additional damage. However, with the right set of skills, it’s sometimes possible to achieve the unthinkable. As [Master Liu] demonstrates, you can indeed repair a broken ribbon cable, even a tiny one.

The video concerns a ribbon cable linked to a Touch ID fingerprint sensor from an Apple device. It’s common to break these ribbon cables when repairing a phone, and doing so causes major problems. The Touch ID device is paired with the host phone, and cannot easily be replaced. Thus, repair is justified if at all possible.

The repair involves scraping back the outer coating on the two sections of ribbon cable to reveal the copper pads underneath. The copper is then coated with flux and solder to prepare them to be rejoined. Ultra-fine strands of wire are used to join the individual traces. Then, the repaired section is coated in some kind of sealant or epoxy to hold the joint together and protect it from failing again. The theory is easy, it’s just the execution that’s hard.

Ribbon cable repair is becoming one of our favorite topics of late. Sometimes you just need a steady hand and the guts to have a go. Video after the break.

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M1 Development Board From Scraps

May 18, 2024 by Bryan Cockfield 29 Comments

Apple is fairly notorious for building devices that are difficult to repair, but with the right tools it’s often not completely impossible to circumvent some of their barriers. As they say, every lock has a key. [dosdude1] has wanted a specific M1 development board for a while now and has been slowly piecing together everything he needs to cobble one together, and finally got this unit running despite many roadblocks put in his way by Apple.

The development kit is a Developer Transition Kit or “DTK” meant for developers during Apple’s transition from Intel chips to their own in-house ARM-based M1 platform. This particular version is in a Mac Mini form factor but it has a few hurdles to clear before it powers on. First, the board was cut in a critical location that shorted out many of the PCB layers, so this had to be carefully filed down to remove the shorts. It was also missing a few tiny surface mount components and a NAND chip, but these were scavenged from other scrapped parts and assembled into a fully working machine.

There are a number of other non-physical problems to solve here as well, too. Apple coded their NAND chips to work with specific WiFi modules so if these aren’t programmed to work together the computer will get stuck in a boot loop. But with that and a few other details out of the way [dosdude1] finally has his DTK up and running in a 2018 Mac Mini chassis, right down to the working power LEDs. We’ve seen all kinds of PCB damage before (although not often quite this intricate) and even PCBs repaired that were snapped in half.

Thanks to [CodeAsm] for the tip!

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