Autopsy Of A Freshly Cooked 10Gbit SFP+ Network Adapter

June 20, 2026 by Maya Posch 20 Comments

With the advent of affordable 2.5 Gbit, 5 Gbit, and 10 Gbit consumer networking gear, more and more people are taking advantage of these higher networking speeds, with [This Does Not Compute] having used 10 Gbit SFP+ modules over regular Cat-5e copper to connect to a NAS in the next room. Only problem was that after a while these SFP+ modules began to start dropping frames. On taking a closer look at these modules, he found that they were running pretty hot: 40°C while idle. A teardown of one of these modules showed severe discoloration due to heat.

Side view of the SFP+ module's PCB. (Credit: This Does Not Compute, YouTube) — Side view of the SFP+ module’s PCB. (Credit: This Does Not Compute, YouTube)

Inside these 10Gbit modules is the Marvell-branded Alaska X 88X3310/40P PHY, which despite the ‘low-power’ claims have a metal heatsink glued onto the actual IC and thermally coupled to the module’s metal enclosure. The other side of the PCB was quite discolored, further indicating how hot these modules run in operation. Some digging revealed that this can go up to around 2.5 watts.

Perhaps the most fascinating part of this teardown is the discovery of an 8051-based MCU that’s responsible for telling the switch the module is put into that it is a 30-meter multi-mode fiber module, presumably for compatibility purposes. It’s definitely an interesting feature of these FS-branded SFP+ modules.

These old modules were replaced with Wiitek-branded modules that are supposed to use only up to around 1.5 watts in operation courtesy of a newer chipset, in the hope that these wouldn’t fry themselves. At idle these do however still run at 30 °C. As noted in the comments, it might be a good idea to have active airflow over high-speed networking gear like this, as they generally can get pretty hot and sometimes crispy.

The final solution for the video’s networking problem was to just run single-mode fiber to the room and use appropriate SFP+ modules for that, also because these run noticeably cooler. If you still have room in your cable ducts, that would seem to be the optimal solution.

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Autopsy Of A Failed Vintage Carbon Resistor

May 27, 2026 by Maya Posch 6 Comments

Detail of the lead connecting to the inner carbon-filled tube. (Credit: CuriousMarc)

Although resistors are hardly among the most exciting components, they are arguably one of the most important ones, as anyone who has done any amount of circuit design and debugging can attest to. So too with a single carbon resistor in a vintage Metrix oscilloscope that [CuriousMarc] recently repaired. After recapping the board there was still a major issue that got traced down to said resistor. After replacing it with a fresh resistor obviously this meant doing an autopsy to see why the old resistor had failed.

The 20 kOhm-rated resistor looked fine on the outside, with no obvious damage or discoloration, but it measured around 0.843 MOhm. To get to the insides [CuriousMarc] asked his friend [TubeTime] on how to proceed. The answer here was sandpaper and a lot of patience, and thus the experiment to see how much sanding it takes to get to the core of a fairly big resistor commenced.

Ultimately the insides were revealed, and they turned out to be rather interesting, with what looked like a glass tube filled with what would be the carbon-laden material between the two lead terminals. From poking around a bit at these insides it would appear that the failure mode was a degraded contact between these terminals and the carbon material. Considering that this resistor is many decades old and has gone through many thermal cycles and potentially various kinetic events some fractures are probably to be expected.

Perhaps most fascinating is the construction of this carbon resistor that looks to be a step above that of the average carbon resistor that [TubeTime] has taken apart over the years.

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Cooking A Raspberry Pi FireWire HAT With Backfeeding

April 15, 2026 by Maya Posch 7 Comments

Recently [Jeff Geerling] has been tinkering with FireWire in order to use some older gear, which includes the use of a Raspberry Pi HAT called the Firehat. This provides a 6-pin FireWire port courtesy of the VIA VT6315N PCIe-to-FireWire chipset. As is typical with USB gear today as well, some FireWire gear requires more power than a port can provide, requiring the use of a powered hub. Unfortunately the use of a powered FireWire hub caused a bit of a conflagration event on [Jeff]’s desk.

Part of the issue appears to be that this Firehat board was designed as a companion to the Equip-1 DV capture device, with no attention paid to the idea that someone might be backfeeding power from an attached hub. As a result the VIA chip cried uncle and let out the magic smoke.

With this Firehat board taking its name clearly a bit too literal, [Jeff] will be reporting his findings to the developers, in the hope that perhaps some diodes or another solution against backfeeding can be added to the final design. Fortunately he was sent this board for testing prior to public release, so this definitely shows a clear flaw that can now be corrected.

We hope that [Jeff] has a good HEPA air filtration setup in his office to get rid of the acrid magic smoke, as it’s not meant to be enjoyed for long periods.

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Post-Failure Autopsy And Analysis Of An LFP Battery

April 2, 2026 by Maya Posch 8 Comments

Recently [Kerry Wong] had one of his Cyclenbatt LiFePO₄ batteries die after only a few dozen cycles, with a normal voltage still present on the terminals. One of the symptoms was that as soon as you try to charge it, the voltage goes up very rapidly to above 14 V due to what appears to be high internal resistance, and vice versa for discharging. In addition, the Bluetooth feature of the BMS appeared to have died as well, making non-invasive diagnostics somewhat tricky.

Close-up of the BMS. (Credit: Kerry Wong, YouTube)

After gently cutting open the plastic case, [Kerry] was greeted by the happily blinking blue LED of the Bluetooth module and deepening the mystery. Overall the build quality looks to be pretty good, with no loose cables as seen with certain other LFP batteries.

Cell voltages measured normal, with no significant imbalance. Next was measuring the internal resistance, which showed a clear issue. One of the cells was reading over 3 Ohms, whereas the others were in the milli-Ohm range. This would definitely explain the issues with charging and discharging, with a single bad cell causing most of the issues.

Of course, why the Bluetooth feature failed remains a mystery, and there’s still a lingering question on whether the BMS practiced proper balancing between the cells, as this can also cause issues over time.

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A Failed SwitchBot Plug Mini And Cooking Electrolytics

February 7, 2026 by Maya Posch 10 Comments

Poorly designed PCBs and enclosures that slowly cook the electrolytic capacitors within are a common failure scenario in general, but they seem especially prevalent in so-called Internet-of-Things devices. The SwitchBot Plug Mini that [Denki Otaku] took a look at after many reports of them failing is one such example.

The location of the failed electrolytic cap in the SwitchBot Plug Mini. (Credit: Denki Otaku, YouTube)

These Mini Plugs are ‘smart’ plugs that fit into a regular outlet and then allow you to control them remotely, albeit not integrated into a wall or such like the Shelly 2.5 smart relay that also began dying in droves. Yet whereas with the Shelly relays this always seemed to take a few years to show up, generally in the form of WiFi connectivity issues, these SwitchBot plugs sometimes failed within weeks or start constantly switching the relay on and off.

After SwitchBot started an exchange program for these plugs, [Denki Otaku] decided to examine these failed devices from affected users. Inside a dead unit the secondary side’s 680 µF capacitor was clearly bulging and had cooked off its electrolyte as a teardown of a dead capacitor confirmed. After replacing this one capacitor a formerly unresponsive plug sprung back to life.

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White LED Turning Purple: Analyzing A Phosphor Failure

May 30, 2025 by Maya Posch 32 Comments

White LED bulbs are commonplace in households by now, mostly due to their low power usage and high reliability. Crank up the light output enough and you do however get high temperatures and corresponding interesting failure modes. An example is the one demonstrated by the [electronupdate] channel on YouTube with a Philips MR16 LED spot that had developed a distinct purple light output.

The crumbling phosphor coating on top of the now exposed LEDs. (Credit: electronupdate, YouTube)

After popping off the front to expose the PCB with the LED packages, the fault seemed to be due to the phosphor on one of the four LEDs flaking off, exposing the individual 405 nm LEDs underneath. Generally, white LEDs are just UV or 405 nm (‘blue’) LEDs that have a phosphor coating on top that converts the emitted wavelength into broad band visible (white) or another specific wavelength, so this failure mode makes perfect sense.

After putting the PCB under a microscope and having a look at the failed and the other LED packages the crumbled phosphor on not just the one package became obvious, as the remaining three showed clear cracks in the phosphor coating. Whether due to the heat in these high-intensity spot lamps or just age, clearly over time these white LED packages become just bare LEDs without the phosphor coating. Ideally you could dab on some fresh phosphor, but likely the fix is to replace these LED packages every few years until the power supply in the bulb gives up the ghost.

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Fault Analysis Of A 120W Anker GaNPrime Charger

May 21, 2025 by Maya Posch 39 Comments

Taking a break from his usual prodding at suspicious AliExpress USB chargers, [DiodeGoneWild] recently had a gander at what used to be a good USB charger.

The Anker 737 USB charger prior to its autopsy. (Credit: DiodeGoneWild, YouTube) — The Anker 737 USB charger prior to its autopsy.

Before it went completely dead, the Anker 737 GaNPrime USB charger which a viewer sent him was capable of up to 120 Watts combined across its two USB-C and one USB-A outputs. Naturally the charger’s enclosure couldn’t be opened non-destructively, and it turned out to have (soft) potting compound filling up the voids, making it a treat to diagnose. Suffice it to say that these devices are not designed to be repaired.

With it being an autopsy, the unit got broken down into the individual PCBs, with a short detected that eventually got traced down to an IC marked ‘SW3536’, which is one of the ICs that communicates with the connected USB device to negotiate the voltage. With the one IC having shorted, it appears that it rendered the entire charger into an expensive paperweight.

Since the charger was already in pieces, the rest of the circuit and its ICs were also analyzed. Here the gallium nitride (GaN) part was found in the Navitas GaNFast NV6136A FET with integrated gate driver, along with an Infineon CoolGaN IGI60F1414A1L integrated power stage. Unfortunately all of the cool technology was rendered useless by one component developing a short, even if it made for a fascinating look inside one of these very chonky USB chargers.

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