Hackaday Prize 2023: Circuit Scout Lends A Hand (Or Two) For Troubleshooting

Troubleshooting a circuit is easy, right? All you need is a couple of hands to hold the probes, another hand to twiddle the knobs, a pair of eyes to look at the schematic, another pair to look at the circuit board, and, for fancy work, X-ray vision to see through the board so you know what pads to probe. It’s child’s play!

In the real world, most of us don’t have all the extra parts needed to do the job right, which is where something like CircuitScout would come in mighty handy. [Fangzheng Liu] and [Thomas Juldo]’s design is a little like a small pick-and-place machine, except that instead of placing components, the dual gantries place probes on whatever test points you need to look at. The stepper-controlled gantries move independently over a fixture to hold the PCB in a known position so that the servo-controlled Z-axes can drive the probes down to the right place on the board.

As cool as the hardware is, the real treat is the software. A web-based GUI parses the PCB’s KiCAD files, allowing you to pick a test point on the schematic and have the machine move a probe to the right spot on the board. The video below shows CircuitScout moving probes from a Saleae logic analyzer around, which lets you both control the test setup and see the results without ever looking away from the screen.

CircuitScout seems like a brilliant idea that has a lot of potential both for ad hoc troubleshooting and for more formal production testing. It’s just exactly what we’re looking for in an entry for the Gearing Up round of the 2023 Hackaday Prize.

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BIOS POST Card Built Using Raspberry Pi Pico

A computer’s BIOS includes basic diagnostic tools for troubleshooting issues. Often, we rely on the familiar beeps from the POST system for this reason. However, error codes are also available via hardware “POST Cards” that were particularly popular in the 1990s. [Mr. Green] has now built a POST card using readily-available modern hardware.

[Mr. Green] built the device to help troubleshoot an x86 based firewall appliance that was having trouble. Like many x86 systems, it featured a Low Pin Count (LPC) bus which can be used to capture POST troubleshooting codes. By hooking up a Raspberry Pi Pico to the LPC bus on the firewall’s motherboard, it was possible to get it to display the POST error codes on some LEDs. This is of great use in the absence of a conventional PC speaker to sound the error out with beeps.

The build can be used for POST-based troubleshooting on any x86 system with an LPC bus. Files are on Github for those eager to replicate the build. We’ve seen similar work before, too. Video after the break.

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the Caps Wiki logo, showing a few bulging capacitors, with "Caps Wiki" text under it

Caps Wiki: Place For You To Share Your Repair Notes

A right-to-repair battle is being waged in courts. The results of it, we might not see for a decade. The Caps Wiki is a project tackling our repairability problem from the opposite end – making it easy to share information with anyone who wants to repair something. Started by [Shelby], it’s heavily inspired by his vintage tech repairs experience that he’s been sharing for years on the [Tech Tangents] YouTube channel.

When repairing a device, there are many unknowns. How to disassemble it? What are the safety precautions? Which replacement parts should you get? A sporadic assortment of YouTube videos, iFixit pages and forum posts might help you here, but you have to dig them up and, often, meticulously look for the specific information that you’re missing.

The Caps Wiki talks a lot about capacitor replacement repairs – but not just that. Any device, even modern ones, deserves a place on the Caps Wiki, only named like this because capacitor repairs are such a staple of vintage device repair. You could make a few notes about something you’re fixing, and have them serve as help and guideline for newcomers. With time, this won’t just become a valuable resource for quick repairs and old tech revival, but also a treasure trove of datapoints, letting us do research like “which capacitors brands or models tend to pass away prematurely”. Plus, it also talks about topics like mains-powered device repair safety or capacitor nuances!

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Cisco Router Repair Revives Piece Of Internet History

It would be fair to say that the Internet as we know it runs on Cisco hardware. While you might never see the devices first-hand, there’s an excellent chance that every web-bound packet leaving your computer or smartphone will spend at least a few milliseconds of its life traveling through hardware built by the San Jose, California based company. But of course, even a telecommunications giant like Cisco had to start somewhere.

Cisco’s first commercial router, the Advanced Gateway Server (AGS), was released in 1986 and helped put the company (and the Internet) on the path towards unfathomable success. [Andreas Semmelmann] had wanted to add one of these microwave-sized machines to his collection for some time, so when an AGS+ popped up in the local classifieds he didn’t hesitate to make the hour drive to go pick it up. But like many pieces of vintage computing equipment, it needed a little help getting back on its feet.

What 4 MB of flash looked like in the late 1980s.

Since he had to take the router apart anyway to diagnose what ailed it, [Andreas] decided to take photographs along the way and document this piece of Internet history. He walks the reader through the massive processor, Ethernet, and serial cards that are housed in the unit’s rack-like enclosure. We appreciate him taking the scenic route, as it gives us a great look inside what would have been state-of-the-art telecommunications gear when this version of the AGS hit the market in 1989.

The walk-through is full of interesting details that make us appreciate just how far things have come in the last 32 years. Imagine yanking the EPROMs out of the board and firing up the UV eraser each time you needed to update your router’s firmware. Or needing a special adapter to convert the AUI-15 connectors on the back panel to the now ubiquitous RJ45 jack.

After this stroll down memory lane, [Andreas] gets to the actual repair work. It likely won’t surprise the regular Hackaday reader to find that the power supply wasn’t operating to spec, and that some aged capacitors and a shorted rectifier diode needed to be replaced to put it back on an even keel. But even with the PSU repaired, the router failed to start. The console output indicated the software was crashing, but hardware diagnostics showed no obvious faults.

Replacing these failed PSU components was just the beginning.

With some part swapping, firmware flashing, and even a bit of assistance from Cisco luminary [Phillip Remaker], the issue was eventually identified as a faulty environmental monitoring (ENVM) card installed in the AGS+. As luck would have it the ENVM capability isn’t required to boot the router, so [Andreas] was able to just disconnect the card and continue on with his exploration of the hardware that helped build the Internet as we know it.

Considering its age, this piece of 1980s Cisco gear ended up being in relatively good shape. But that’s not always the case. Over the years we’ve found ourselves in awe of the incredible amount of time, effort, and skill, it takes to restore some of these classic machines. We have great respect for the dedicated individuals who are willing to take on the challenge of keeping these pieces of history up and running for future generations to marvel at.

[Thanks to Bob for the tip.]

Troubleshooting: A Method For Solving Problems The Right Way

We’ve all experienced that magic moment when, after countless frustrating hours of experimentation and racking your brain, the object of our attention starts working. The 3D printer finally produces good output. The hacked up laptop finally boots. The car engine finally purrs. The question is, do we know why it started working?

This is more important than you might think. Knowing the answer lets you confirm that the core problem was solved, otherwise you may have just fixed a symptom. And lack of understanding means fixing one problem may just create another.

The solution is to adopt a methodical troubleshooting method. We’re talking about a structured problem solving technique that when used properly can help us solve a problem at its core without leaving any loose ends. Such methodology will also leave you knowing why any solution did or didn’t work in the end, and will give you reproducible results.

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Chasing Down Bad Caps To Save A Troubled PSU

We know what you’re thinking. It’s a bad power supply, of course it was capacitors to blame. But even if we all intuitively know at this point that bad caps are almost always the culprit when a PSU gives up the ghost, it’s not always easy to figure out which one is to blame. Which is why this deep dive into a failed ETK450AWT by [eigma] is worth a look.

The first sign of trouble was when the computer would unexpectedly reboot with nothing in the system logs to indicate a problem. Eventually, [eigma] noticed a restart before the operating system even loaded, which confirmed the hardware was to blame. A quick look at the PSU output with a voltmeter showed things weren’t too far out of spec, but putting an oscilloscope on the 12 V line uncovered a nasty waveform that demanded further investigation.

Connecting all the dots.

By carefully following traces and comparing with common PSU diagrams, [eigma] was able to identify the SG5616 IC that checks the various voltages being produced by the PSU and generates the PWR_OK signal which tells the motherboard that everything is working normally. As before, all of the DC voltages at this chip seemed reasonable enough, but the pin that was measuring AC voltage from the transformer was showing the same ripple visible on the 12 VDC line.

Even more digging uncovered that the transformer itself had a control IC nestled away. The 13 VDC required by this chip to operate is pulled off the standby transformer by way of a Zener diode and a couple capacitors, but as [eigma] soon found, the circuit was producing another nasty ripple. Throwing a few new capacitors into the mix smoothed things out and got the PSU to kick on, but that’s not quite the end of the story.

Pulling the capacitors from the board and checking their values with the meter, [eigma] found they too appeared to be within reasonable enough limits. They even looked in good shape physically. But with the help of a signal generator, he was able to determine their equivalent series resistance (ESR) was way too high. Case closed.

While swapping out blown capacitors in older electronics is something of a rite of passage for hardware hackers, this case is an excellent example of how even the simplest of fixes can be tricky to troubleshoot.

Fixing NRF24L01+ Modules Without Going (Too) Insane

Good old nRF24L01+ wireless modules are inexpensive and effective. Well, they are as long as they work correctly, anyway. The devices themselves are mature and well-understood, but that doesn’t mean bad batches from suppliers can’t cause hair-pulling problems straight from the factory.

[nekromant] recently got a whole batch of units that simply refused to perform as they should, but not because they were counterfeits. The problem was that the antenna and PCB design had been “optimized” by the supplier to the point where the devices simply couldn’t work properly. Fortunately, [nekromant] leveraged an understanding of the problem into a way to fix them without going insane in the process. The test setup is shown in the image above, and the process is explained below. Continue reading “Fixing NRF24L01+ Modules Without Going (Too) Insane”