Reviving The PoE++ Feature On A Ubiquiti Switch

September 25, 2026 by Maya Posch 5 Comments

Recently [The Parallel Port] was asked to take a look at repairing the PoE++ feature on a Ubiquiti switch that otherwise worked fine. This is a pretty nice 24-port rackmounted switch with 2.5 Gbit-capable RJ-45 ports and two 10 Gbit SFP+ ports, so by itself it’s pretty useful, but having the 400 Watt PoE feature just go AWOL still stings, especially if you bought it new for $800.

With power applied the switch starts up as normal, including its 1.3″ touch screen that provides direct port information as well as a fancy screensaver cum QR code for the AR feature.

After logging into the switch’s BusyBox console it showed that all ports reported bad for the PwrGood status, and there were PoE power status request errors in the log, but this could be just the consequence of something else. Using a PoE splitter it was confirmed that the PoE functionality was indeed dead.

After disassembly and some testing with a multimeter and thermal camera, a short and related hot spot on the PCB that the PoE power board connects to was identified, with the short persisting after removing this PCB from the switch. Since the switch had suffered a bit of an electrical event the TVS diode was checked, but it turned out to be fine.

Next to it, marked as fuses, were protective thyristor surge protection devices (Trisil), functioning as a crowbar device. These aren’t supposed to be shorted to ground until a surge event occurs, but these were indeed both shorted when measured directly. Clearly they had taken the brunt of the electrical event and sacrificed themselves in the process.

One replacement later of these devices the switch now happily reports a good PoE status and even was able to power a DC fan via the PoE splitter. Even if it wasn’t a particularly hard fix, this is definitely one of those cases where knowing how the protective circuit works can save a lot of time in diagnosing and fixing a fault.

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Teardown And Repair Of An Insoma Water Timer

September 19, 2026 by Maya Posch 5 Comments

Water timers are nifty devices that can water the lawn at set times or keep that vegetable garden from turning into a dustbowl. When [electronupdate] timer refused to output water on any of its three outlets, he did the right thing. Instead of angrily checking the warranty on the sodding thing, he tore it apart to attempt a repair.

As expected, the design of these devices is quite straightforward. Three solenoids control whether an outlet is open or closed. A control board also handles the user controls and display.

There was no obvious sign of damage, and the PCB was potted in a white substance that should have kept out any moisture. A quick check with a battery revealed that the three solenoids also worked just fine, so the cause likely was somewhere on the — potted — PCB.

These solenoids are rated for 6VDC and take about 20 ms to act, but on an oscilloscope capture it was plain to see that the board was only putting out around 2V. This wasn’t enough to drive the solenoid, raising the question of what had gone wrong on the controller board and setting the stage for some fun epoxy potting compound scraping.

A good bit of elbow grease revealed the control ICs, the H-bridges that drive the solenoids, and the rest of the circuitry, including a power boost circuit with a big electrolytic capacitor. The latter had a bit of suspicious liquid near its base, which turned out to be the culprit. Perhaps the most annoying thing here is that this electrolytic capacitor had the temerity to fail after only four months of use, but at least it was an easy enough fix.

If we had been in there, we might have been tempted to avoid many future battery changes. Impractical, but we wonder if anyone ever built a water timer with a water clock?

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Reconstructing A Pin On A Pin Grid Array Package

September 18, 2026 by Maya Posch 14 Comments

Before moving to land grid array (LGA) packaging whereby each pin on the substrate is just a copper pad, processors commonly used pin grid array (PGA) packaging, including the still highly relevant AMD AM4 socket. With PGA you get a pin soldered onto the copper pad which inserts into the ZIF socket, rather than a fragile pin on the mainboard side. Repairing a damaged PGA pin can be easy if just the pin broke off at the solder joint, or rough if the pad was destroyed, as in the case of this Pentium III CPU that [Bits und Bolts] recently tried to fix.

In the case of something like a ground pin or similarly unimportant pin you can ignore the damage, but in this case it concerned an important pin for this 1.2 GHz Tualatin PIII core, with the damage consisting of a well and truly destroyed pad. The first step to repair the damage is thus to try and rebuild the pad, which was done using solder mask and solder.

Although a PIII-era Celeron CPU is definitely not a high-value CPU, since they have so few and such large pins they do make for useful test subjects when it comes to PGA repair practicing. In this case the affected data pad and pin appears to have been repaired successfully, with it running overclocked to 1.6 GHz and crushing similarly or higher clocked Pentium 4 and AMD Athlon CPUs of the era.

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After 6 Years As Road Ornament A Widescreen Sony Trinitron Lives Again

September 15, 2026 by Maya Posch 19 Comments

After previously adopting a big Sony Trinitron CRT TV that had been trying to hitch a ride along the side of a road in Italy for at least six years, [Happychoice] didn’t give up on trying to fix it, with the second part showing the TV being more or less fully fixed up.

In the first part of this mini-series, the TV had been salvaged and had most of the dirt as well as local flora and fauna evicted before an attempt was made to fix it. Unfortunately despite the insides looking remarkably clean and intact considering its use as a road-side ornament, that video ended with the controller refusing to power up due to issues with the power supply.

In this sequel we get to see what six years of weather exposure means in terms of what components to replace in a CRT TV like this. Unsurprisingly this means mostly replacing most of the capacitors, at least on the power supply board, as well as the neck board for the actual CRT. A couple of MOSFETs also tested open, so they were replaced too.

With those fresh new parts the TV fired right up again, and with a Wii console connected it looks pretty spiffy running games like Persona 4. Fortunately modern CRT TVs like these have a built-in service menu that you can access with the remote, so that you can tweak picture alignment and other settings without having to stick a screwdriver into the back of the TV to fiddle with a potentiometer whilst also keeping an eye on the picture.

Although there are undoubtedly more components on the PCBs and of course one grimy speaker to give some TLC, it does show that as long as the tube itself is intact, it’s definitely worth it to give repairing a shot.

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Fixing A Ubiquiti 16-Port PoE Switch With An Extra Hole

September 15, 2026 by Maya Posch 7 Comments

After saving a £300, 16-port Ubiquiti network switch from getting tossed into the trash, [Buy It Fix It] got the honor of trying to repair it. With four ports and their associated PoE function having some major issues it looked like it might take some debugging, but after taking the lid off, the cause seemed rather obvious.

One of the Broadcom BCM5911 controller chips had a rather suspicious chip of the plastic packaging missing, with additional probing of connected components showing that numerous MOSFETs and a diode having had their proverbial guts blown out and were shorted as well. Whatever happened to some connected Ethernet device would appear to have left a serious trail of damage that nearly wrecked the entire switch.

The biggest challenge here was probably to find a replacement for the Broadcom IC, as this isn’t an IC that stores like Digikey or Mouser stock any more. Fortunately it was still available for sale over at AliExpress for £1.84, with the usual caveat that it could be salvage, fake, a factory reject, etc. In this case it appears that it was a legit Broadcom IC, with the four affected ports springing back to life including powering a PoE camera.

With a total cost of about £5 plus the time invested it wasn’t a bad deal to save a pretty nice PoE switch with 16 Ethernet and 2 SFP ports.

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Fixing A 1990s LEGO Electric Train Speed Regulator

September 8, 2026 by Maya Posch 20 Comments

Before LEGO train sets moved to battery-powered locomotives with plastic rails, all of them worked pretty much like any other train set of the era. This meant metal rails that the locomotive’s wheels would use to pick up power from and a central controller that would inject said power and also regulate the train’s speed and direction. The LEGO 2868b Electric Train Speed Regulator is one such example, and [Nonsense Wars] recently had one under the knife to repair it.

The single PCB inside is quite straightforward, with the 9-12 VAC supply input from an external power adapter, and a variable voltage regulator that sees its target voltage switched by a bank of resistors.

It are these resistors that the big yellow control switches between when you operate it, changing the output voltage and also output polarity you cross the midway point. Effectively this means that there is just one non-passive component on the PCB, in the form of the TO-220 package strapped to the big heatsink.

In this particular unit it was found to be a Fairchild KA317, which is for all intents and purposes here the same as an LM317T. One quick swap later and this controller was back in business like it was 1995.

Compared to the engineering crammed into a modern “smart brick”, things really have come quite a ways in the world of LEGO.

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Fixing An Expensive Seagate LaCie Hard Drive Array

September 4, 2026 by Maya Posch 14 Comments

After the [Slow Mo Guys] acquired a 168 TB Seagate LaCie Thunderbolt 3-based RAID storage system back in 2019 to store their video footage, they were obviously slightly miffed when suddenly it would just refuse to power up. Naturally the device was now out of warranty, the product itself no longer produced and Seagate support was less than supportive, ergo they sent the device to [Mend it Mark] for an attempted repair.

At first inspection the device appeared to be basically unresponsive, with none of the four fans running and no signs of life other than a few lit LEDs on the main PCB after supplying power to it. After full disassembly and with no repair guide or schematics to go by [Mark] had to start from basics, first diagnosing whether all the power rails were turning on, which they weren’t.

Eventually this led to the NXP LPC11U6x-series MCU which acts as the main power management and monitoring chip in the system. [Mark] deduced that this MCU wasn’t turning on all the power rails because it was waiting for a signal from the fan controllers on the SATA backplane. With the MCU sending the right signals here, and the fans all working when directly supplied with power, ultimately it turned out that a single SI2319 or similar P-channel MOSFET in SOT-23 package near one of the fan connectors had gone faulty.

Replacing this one MOSFET seems to have fixed the RAID array, with it now happily powering up, although the real test will be once the [Slow Mo Guys] start shoving the HDDs back into it. Assuming that this was the sole fault in the system, then it was a very cheap fix in terms of materials. It’s a real shame that repair guides or schematics aren’t made available for devices like this, even if just after they stop being produced.

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