Repair Hacks

577 Articles

Kim-1: Memory Problem Resolved

July 10, 2023 by 20 Comments

At the very start of the personal computer revolution, there were relatively inexpensive boards with little more than a CPU, some memory, a display, and switches or a keypad. Some of these had expansion ports meant to allow you to build up, and some were just “trainers” to learn about computers. While you could argue that the Altair fell into this category, it had a case and a proper bus. The computers we are thinking about were usually just on a single board and — with luck — had an edge connector for expansion. Perhaps the most famous of these was the KIM-1 and [Old VCR] shows us how he brought one back to life.

These were highly popular mainly because of the low price of $245 back in 1976. For that price you got a calculator-style keyboard and LED display, 1K of RAM, and 2K of ROM. [Old VCR] has several and noticed that one was developing memory problems.

Continue reading “Kim-1: Memory Problem Resolved” →

A Faulty Keyboard From A Single LED

July 5, 2023 by 19 Comments

When the chance arrived to buy a mechanical keyboard for not a lot, naturally, [Hales] jumped at it. Then it started having odd intermittent problems with some keys appearing stuck, which led to a teardown and some fault finding. The culprit was a white LED — but why this was the case is a fascinating story.

Stripping it down there didn’t seem to be an obvious culprit, but eventually, the trail led to a lack of diodes in the matrix. This keyboard had an extremely clever yet rather cursed design in which it used LEDs as both illumination and as a diode in the keyboard matrix circuit, and the faulty LED had a reverse breakdown condition that could be triggered under certain operational conditions.

More unexpectedly, it would sometimes hold on to its reverse breakdown state even after power off. Just when you think you understand a component’s properties, there’s always room for surprise. And we can safely say we’ve learned something about the design of cheaper keyboards in reading the account. It’s clear that when it comes to ‘boards, it’s best to take no chances.

A Dusty Boat Anchor Back From The Brink

July 4, 2023 by 16 Comments

Many of us will have found dusty forgotten pieces of electronics and nursed them back to health, but we were captivated by [Don]’s tale of electronic revival. Instead of perhaps a forgotten computer or television, his barn find was a Heathkit linear amplifier for radio amateurs. In that huge box underneath an impressive layer of grime were a pair of huge tubes, along with all the power supply components to give them the 2 kV they need. It should have been good for a kilowatt when new, can it be made to go on air again?

Perhaps understandably with such an old device, after cleaning away the dust of ages he replaced the power supply circuitry with new parts and PCBs. A linear amplifier is surprisingly simple, but because of the voltages and power concerned there’s a need to treat its power circuits with respect. On first power-up the filaments work and the rails come up, so when given some RF drive it comes alive. Coupled with a case restoration you’d never know how dreadful a state it had been in.

We like to see classic Heathkit devices here at Hackaday, though we’ve followed their more recent reappearance too.

An HP9863C partially disassembled on a workbench

Repairing A $25,000 HP Workstation To Run Pac-Man

June 20, 2023 by 21 Comments

The microcomputer revolution of the 1970s and 1980s turned computers from expensive machines aimed at professionals into consumer products found in the average household. But there always remained a market for professional users, who bought equipment that was so far ahead of consumer gear it seemed to belong in a different decade. While a home computer enthusiast in 1981 might fork out a few hundred dollars for an 8-bit machine with 64 KB of memory, a professional could already buy a 32-bit workstation with 2.8 megabytes of RAM for the price of a brand-new sports car. [Tech Tangents] got his hands on one of those machines, an HP Series 200 9863C from 1981, and managed to get it up and running.

The machine came in more-or-less working condition. The display cable turned out to be dodgy, but since it was just a straight-through sub-D cable it was easily replaced. Similarly, the two 5.25″ floppy drives were standard Tandon TM100-2As which [Tech Tangents] had some experience in repairing, although these specific units merely needed a thorough cleaning to remove forty years’ worth of dust. Continue reading “Repairing A $25,000 HP Workstation To Run Pac-Man“ →

Hacking Headaches: Keeping A Neurostimulator Working

June 13, 2023 by 11 Comments

We’ve heard a ton of stories over the years about abandoned technology — useful widgets, often cloud-based, that attracted an early and enthusiastic following, only to have the company behind the tech go bankrupt or decide to end operations for business reasons, which effectively bricks hundreds or perhaps millions of otherwise still-usable devices. Now imagine that happening to your brain.

[Markus Möllmann-Bohle] doesn’t have to imagine it, because he’s living it. [Markus] suffers from chronic cluster headaches, an often debilitating condition that leaves a person with intractable pain. Having lived with these headaches since 1987, and treating them with medications with varying degrees of success, [Markus] was finally delivered from his personal hell by a sphenopalatine ganglion (SPG) neuromodulator. The device consists of an unpowered stimulator implanted under the cheekbone that’s wired into the SPG, a bundle of nerves that supply the sinuses, nasal mucosa, tear glands, and many other structures in the face.

To reverse a cluster headache, [Markus] applies an external transmitter to the side of his face, which powers the implant and directs it to stimulate the SPG with low-frequency impulses, which interferes with a reflex loop that causes the symptoms associated with a cluster headache. [Markus] has been using the implant for years, but now its manufacturer has rolled up operations, leaving him with a transmitter in need of maintenance and the possibility of facing his debilitating headaches once again.

The video below shows [Markus]’s workaround, which essentially amounts to opening up the device and swapping in a new LiPo battery pack. [Markus], an electrical engineer by training, admits it’s not exactly a major hack, but it’s keeping him going for now. But he’s clearly worried because eventually, something will happen to that transmitter that’s beyond his skills to repair.

There’s cause for hope, though, as the intellectual property of the original implant company has been purchased by an outfit called Realeve, with the intention to continue support. That would be a lifesaver for [Markus] and everyone relying on this technology to live a normal life, so here’s hoping there’s no need for future hacking heroics. But as the video below details, there is a lot of neurotechnology out there, and the potential for having that bricked by a corporate decision has to be terrifying to the people who depend on them. Continue reading “Hacking Headaches: Keeping A Neurostimulator Working” →

Do Not Attempt Disassembly: Analog Wizardry In A 1960s Counter

June 12, 2023 by 22 Comments

[CuriousMarc] is back with more vintage HP hardware repair. This time it’s the HP 5245L, a digital nixie-display frequency counter from 1963. This unit is old enough to be entirely made of discrete components, but has a real trick up its sleeve, with add-on components pushing the frequency range all the way up to 18 GHz. But this poor machine was in rough shape. There were previous repair attempts, some of which had to be re-fixed with proper components. When it hit [Marc]’s shop, the oscillator was working, as well as the frequency divider, but the device wasn’t counting, and the reference frequencies weren’t testing good at the front of the machine. There were some of the usual suspects, like blown transistors. But things got really interesting when one of the boards had a couple of tarnished transistors, and a handful of nice shiny new ones — but maybe not all the right transistors. Continue reading “Do Not Attempt Disassembly: Analog Wizardry In A 1960s Counter” →