Extracted Magnets from Wired Earbuds

Headphone jacks are disappearing from recent phones, which is a shame. Thanks to global volume, wired earbuds have become simple and effective accessories for audio on-the-go. So inexpensive as to be practically disposable, the price fits with the fact they have a finite and short lifespan. As the wires flex and bend, they eventually break and cause intermittent connections audible as cracks and pops. Which was why this particular set (Monoprice #18591) was retired.

Compact and lightweight, there’s hardly any material here at all to reclaim or recycle. But there’s a small rare earth magnet inside each earbud, and I want to extract them before the remaining carcass heads to the landfill. Similar to what I did to a retired iPad cover case.

These earbuds had been waiting processing for a while, hence the dust.

The soft rubber layer pops off easily. As I recall this was a user-replaceable item. The earbuds came with three sizes. The midsize one is installed by default, with smaller and larger sizes in the package the user can switch to best match the size of their ear canal.

There were no further user-serviceable parts. Everything else is molded or glued together so I had to break things apart with a pair of pliers.

Inside the black plastic enclosure is a shiny metal case for the tiny soundmaker.

Prying off the front metal plate exposes the thin membrane that vibrates with a small copper coil. Inside the center of that copper coil is the magnet I seek.

The magnet is glued to the enclosure, but thankfully the glue here wasn’t very strong. Bending the sheet metal to get more clearance, I was able to reach in with a thin metal tool and pop out the magnet.

Attached to the magnet is a thin metal circle of the same diameter. I think it serves as a spacer, held on by the same not-very-strong glue so I could separate it from the magnet.

Here’s the entire stack disassembled. Circled in red square is the magnet I will keep. Remainder will head to landfill.

Nokia Lumia 520 (RM-915) Teardown

I enjoyed exploring leading edge web development with experimental features like magnetometer API and evolving standards like PWA. But learning about the trailing edge also has some value for me. I have a stack of old Windows Phone 8 devices. Microsoft had shut down native app development for the platform as part of its end-of-life treatment, leaving its onboard web browser as the only remaining entry point. Based on Internet Explorer 11, support of which has been dropping from platforms left and right, there’s definitely a clock ticking away if I want to be able to do anything with those phones.

Assuming, of course, those phones don’t decay and die on their own like this Nokia Lumia 520 has done. It’s been a guinea pig to test things like ESA’s ISS tracker web app. When I turned it on recently, it failed to boot and crashed to this blue screen of death. Unlike its desktop Windows equivalent, there are no debug information printed onscreen. Documentation has been purged from Microsoft and Nokia websites as they have disowned these devices. So, it was up to iFixit to preserve documentation on performing factory reset with a hardware key sequence: From powered off state, hold [volume down] and press [power] to start phone. As soon as phone vibrates, release [power]. Once phone boots to exclamation mark, release [volume down]. Press key sequence [volume up], [volume down], [power], [volume down]. Watch spinning gear onscreen for a few minutes.

But performing such a reset on this phone didn’t help, I just ended back at the sad faced blue screen of death. I don’t know what happened to this phone. I hadn’t thought electronics would decay with time, but something on this one has failed in a way I lacked information or tools to diagnose. I powered up my remaining Windows Phones and they were able to boot, so it’s not a common/widespread failure mode. (Yet?) In any case, today this dead phone gets the teardown treatment.

Nokia Lumia 520 was a simple and basic entry-level phone, dating back to the era when batteries were easily accessible and removable by the user. Not so much anymore, which is sad though there are occasional encouraging signs. Popping off the easily-removed blue back cover, we see physical features like a microSD card slot, SIM slot, and headphone jack. All useful features disappearing from modern phones.

The next layer is a black plastic cover held by multiple Torx fasteners and plastic clips. Removing that cover exposes phone mainboard, where we can see the thickest component is the rear-facing camera. It actually sits in the middle of a hole cut out of the circuit board, protruding both in front and behind of the board. (Lumia 520 does not have a front-facing camera.)

Ribbon cable near the top of the device is for touch digitizer input via this Synaptics chip.


Sadly, a web search with engraved text failed to return anything useful.

The touch controller communicated with the rest of the phone with ten wires, but they are far too fine-pitched for my current skill level to work with.

It’s a similar story with the LCD, connected to mainboard with twenty wires. Far too few to directly control an 800x480x3 LCD array, these must be data buses communicating with a controller somewhere downstream. At least six of these wires visibly hint at differential signal pairs.

Front and back views of removed mainboard. Full of tiny components, most of which hidden under RF shields, I see only two components (battery connector and vibration motor) that I could realistically repurpose.

With mainboard removed, I see no further fasteners to remove, and no obvious seams.

I knew it was too complex to be a single piece, so I manually twisted the assembly looking for signs of seams between parts. Attacking candidates with iFixit picks allowed me to separate the front panel touch digitizer from display subassembly.

The display assembly is held to its chassis frame with a few strips of adhesives and could be carefully peeled apart.

Freed from its structural frame, the display assembly feels very delicate. It easily flexes and twists to reveal details like these side-emitting LEDs for backlight illumination.

Peeling back foil tape uncovered ultra fine-pitched LCD array control wires embedded between layers of glass.

Trying to separate LCD array from backlight, I unfortunately cracked the glass and destroyed the LCD. I might be able to reuse the LED backlight but it’s going to be a serious challenge finding (and soldering to) those fine wires for LED power.

Goodbye, Nokia Lumia 520. I’m sad I didn’t get around to finding something interesting to reuse you as a whole unit. And your component parts are mostly too tiny for my current skill level to work with. But your death gave me a kick in the pants to get on with my studies. I hope to make use of your surviving contemporaries.

Snow Globe Liqueur LED

This Christmas themed novelty product “Snowglobe Orange & Gingerbread Gin Liqueur” is an alcohol beverage packaged in a globular glass bottle resembling a snow globe. Contributing to the theme is a small quantity of edible gold flakes in the liquid that can float like snowflakes, illuminated by LEDs embedded in the base. I didn’t care about the alcohol, but I asked (and was given) the empty bottle afterwards so I could remove that LED circuit to see an example of low-cost disposable production.

Each press of the bottom toggles LED power on/off. There may be a sleep timer to turn off LED after some period, but I didn’t test that.

The LED circuit board is surrounded by a circle of soft foam, which is in turn glued to the bottle. It peeled off easily.

Four surface-mounted white LEDs are visible, labeled L1 through L4. Each pair (L1+L2, L3+L4) are in series. The two 3V coin-cell batteries are also in series for 6V power supply. Battery positive terminal is connected to both pairs of LED series at their anode (+) and control chip U1. Battery ground is connected to control chip U1 and nowhere else. U1 has six pins: two pins for power and ground, two for LED cathode (one for each pair), and two more for the switch.

Peeling circuit board away from foam, the two switch terminals are visible. Closing this circuit is the job of a small piece of conductive metal, here still held by the bottom sticker. The metal is a thin springy sheet stamped into a dome shape. Pressing and collapsing the dome closes the switch circuit. Releasing the dome lets it pop back up and open the circuit.

Anything that conducts electricity bridged across those circuit board contacts will toggle LED on/off.

This was designed to be thrown away along with the bottle once the alcohol has been consumed. I’ve tossed the bottle into glass recycle bin and I’m keeping the light, even though at the moment I have no use for a dim battery-powered LED circuit with push on/off.

Prepare Salvaged CD/DVD Motor for Test

Using a brushed DC motors is easy: apply voltage, watch motor shaft turn. I’m exploring brushless DC motors and even the cheapest controller from Amazon had features that I hadn’t even known existed. It is far more sophisticated than a DC motor driver (DRV8833) I explored earlier. To make it actually turn a motor, I’ll start simple with the smallest brushless motor I found in my pile of salvaged hardware.

This is a small brushless motor in the spindle of a CD or DVD drive. Based on the fact it is only a few millimeters thick, it was probably salvaged from a laptop optical drive. Lots of wires visible in the pale-yellow ribbon cable. I will need to probe them looking for a set of three or four wires, with a tiny bit of resistance between them, that would indicate coils for the brushless motor.

I probed the set of four contacts closest to the motor, but found no electrical connection between them.

This set of four wires looked promising. They ended abruptly, as if I had cut them off from a larger piece of pale yellow flexible printed circuit. (FPC) I guess the rest of that circuit didn’t look interesting to keep and what they were have been lost to history. I used sandpaper to uncover the copper traces within this cut-off segment. This work was for naught: no electrical connections here either.

This left the large connector of many wires. I noticed the five conductors in the middle are wider than the rest. Each of those led to two contact points on the connector. I started with those and found likely candidates in three of the five wide wires. I’m not sure what the other two were… perhaps power and ground for some other circuit? Whatever they were, I hope they aren’t relevant to my current experiment.

I soldered thin (30 gauge *) wires to each of those points. Using an old AA battery as ~1V source, energizing any two of these wires would result in the motor holding a position. Motor coils confirmed!

A bit of careful cutting and heat-shrink tubing isolated these wires from each other.

Resulting in a motor that I can connect to my brushless motor controller running BLHeli_S firmware.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Intel SSD 320 Series Teardown

After taking apart a hard drive that went to great lengths to be just 5mm thick, I moved on to an SSD whose circuit board of surface-mounted chips were even thinner without even trying. This Intel 320 Series SSD should still be usable today, but it isn’t because of an overzealous security feature.

My Dell Inspiron 15 7577 came with a secure data wipe feature in BIOS and I decided to use it to securely wipe data from this SSD. What was critically missing from its description was that, as part of securing my data, this feature would lock the drive with a password that is never displayed. (“Lock it up and throw away the key.”) This fulfilled the task of securing any data on the SSD, but it made it impossible to reuse the SSD elsewhere. This 300GB capacity SSD cost over $500 in 2012, so I was NOT HAPPY it was rendered unusable. At the time Dell claimed the security feature was Working By Design. Later on, it admitted the behavior was a bug after all and offered BIOS updates to some other computers (not mine) to remove this behavior. Doesn’t matter, I’ve learned my lesson and never used the feature again.

I hung on to this unusable SSD for years, hoping to find a utility that could somehow reset the device and unlock the capacity that Dell overzealously locked away. But now, with new 500GB SSDs available for less than $50, I finally conceded there’s no point.

The thick black plastic shim brought it to 9mm height typical of laptop HDDs but can be removed to fit in spaces designed for thinner 7mm HDDs. It looks bulky next to the 5mm thick WD5000M21K hybrid drive, but that was merely a metal enclosure.

Once removed from its enclosure, we can see an internal circuit board who is barely 3mm thick not counting the SATA connector.

The brain in charge of this operation is Intel’s own PC29AS21BA0 controller.

Data is stored across 20 Intel 29F16B08CCMEI flash memory chips, 10 on the front side and 10 on the back. I hypothesize they are each good for 16GB of raw storage. 20 of them together would give 320GB of raw storage, 300 of which is accessible to user and 20 reserved for SSD housekeeping.

Hynix H55S5162EFA is probably a bit of dynamic memory used by the controller chip to do its job. Intel sold its flash memory division to Hynix, so technically speaking this entire device is now Hynix.

The whole point of secure data wipe (and lock) is to render all data safely inaccessible, so I should be good to stop. But why pass up a chance to play? Just like my previous decommissioned SSD, I’m going to remove those flash chips with my paint-stripping hot air gun. This blunt tool is unsuitable for electronics work if we want delicate devices to work again. But in this case, if the heat should damage a chip beyond repair, that would be a feature and not a bug.

A few minutes later, I had a loose jumble of flash memory and other chips. Even if the heat gun hasn’t destroyed the chips completely, anyone who wants to steal my data will need to figure out which chip went in which location. (I recommend they find a different hobby.)

Western Digital SFF-8784 Hybrid HDD/SSD Teardown (WD5000M21K)

For contrast with the old Toshiba laptop hard drive I just took apart, I decided to follow up with this Western Digital WD5000M21K. This is a hybrid device with both a spinning magnetic platter and flash memory solid-state storage. In theory it is the best of both worlds offering large-capacity (500GB) storage and solid-state drive performance for cached data, all packed in an impressively compact SFF-8784 form factor. It is only 5mm thick! The mechanical engineers must have been fighting for fractions of millimeters designing its innards.

In practice, its performance was abysmal. It was nowhere near SSD level and felt even worse than contemporary HDDs. Its performance was utterly blown away by a M.2 SATA SSD (in an SFF-8784 adapter card) which, because they were just small circuit boards, were effortlessly more compact on top of better performance. Dropping SSD prices have eliminated the niche of compact mechanical hybrid drives. Ending this line of evolution to sit alongside VHS+DVD players in history as transitionary products with a limited shelf life.

One thing that caught my attention was a sticker covering the entire top surface of this device, and it wasn’t even very densely printed with information. As I would learn later, this sticker is not merely cosmetic.

Most product information was actually printed on a sticker on the other side of the device, surrounding the motor where we can see three wires implying a delta style winding. This drive’s control board is much smaller than the older Toshiba drive, even though it had to include a SanDisk-branded chip providing its 8GB of flash memory (“SSD”) cache. Its size was helped by the compact SFF-8784 style connector. A standard SATA connector would have required almost half of the volume of this entire control board.

Returning to the top side, I removed the sticker and saw why it covered everything: it’s a part of this drive’s airtight seal. WIth top sticker gone, an ~1mm gap surrounding the voice coil magnet assembly is now open to outside air.

Most of the Torx fasteners were T2, except for the one at the center of the platter which is even smaller. I assume it is a T1, but I don’t know for sure as I don’t have a driver. I’m using iFixit’s Mako Driver Kit and the smallest Torx bit is a T2. Not even their larger Manta kit has a T1.

Of course, that’s not going to stop me. As I’m not worried about putting it back together, or metal particle contamination, I have the option of drilling off the tiny screw head today. I might not always have that option, though, so to be prepared I found and ordered a driver set (*) because it claimed to include T1.

Once drilled out, I could remove the thin metal top lid and saw a single platter within. (I would have been astounded if they could pack multiple platters in here.) It has a an off-platter parking spot very similar to the Toshiba laptop drive, but it doesn’t have the mystery latch mechanism. After that point I was pretty stuck. I could not figure out how to free the bearing from the voice coil arm. I could not find a way to disassemble that stack. And I could not figure out how to free the platters. For the platters, it appears I need a special wrench that engages with the eight dimples on the spindle and use it as leverage to turn against the four surrounding slots.

As an amusing size comparison, here’s the compact WD5000M21K next to the spindle motor assembly from a 3.5″ sized WD800 hard drive. It’s an impressive feat of engineering, packing all these mechanical components within 5mm of thickness. But technology moves on, and SSDs are far thinner by nature.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Toshiba 2.5″ 250GB SATA HDD Mechanicals (HDD2D90)

A few days ago, I thought I’ve learned enough electronics to get something out of examining circuit boards in consumer electronics. Striking out on this Toshiba 2.5″ hard drive control board immediately after coming up empty on a Western Digital 3.5″ hard drive control board makes me think I’ve overreached too far beyond my skills. No matter, I’m still skilled with a screwdriver and can handle taking apart mechanical components.

Removing a rather large sticker label unveiled just one hidden screw.

After removing those screws, the lid came off easily.

I was surprised to find two platters was packed in this drive less than a centimeter thick representative impressive miniaturization at work. One difference between a desktop drive and this laptop drive is the read-write heads are physically pulled off the platter in parked position. I was under the impression HDD read-write heads are far too fragile for transition a gap between mechanical pieces or rubbing against anything other than a cushion of air. Seeing this tells me they’re not as fragile as I had thought, but I don’t know what the actual engineering constraints involved.

On the opposite end of the pivot, beyond the voice coil actuator, is this mechanism whose purpose I don’t fully understand. The pivoting metal arm could slot into a sharp hook next to the voice coil, keeping the read-write head away from the platter. But how does it know when to engage or not? It works in conjunction with the white plastic part, but I couldn’t figure out how the whole mechanism works together. My best guess is that we have a clever mechanism that would lock the pivot safely in place until the voice coil actuated pivot performs effectively a “secret knock.” Taking advantage of inertia and momentum, the right sequence of motion would release the lock. To verify this hypothesis, I would need to reassemble the drive and see if I can power it up, but by the time I thought of doing so, I had already passed the point of no return.

Because with the mystery latch removed, it was easy to remove the read-write head assembly and once I did, I could not put it back into place.

Flipping it over, I see a hex nut holding the entire stack together.

Loosening and removing the nut allowed disassembly of the entire stack.

I was surprised to find both platters were held by a single screw. Platters for large desktop drives always had multiple fasteners to ensure their platters could not rotate out of place. With a single screw, we don’t have that mechanical guarantee. I guess it’s just friction preventing these platters from rotating relative to each other or the spindle.

I was pretty impressed at how thin and compact this laptop hard drive was, but hard drive engineers have done even better than this.

Toshiba 2.5″ 250GB SATA HDD Control Board (HDD2D90)

I’ve taken apart countless numbers of 3.5″ desktop hard drives like a Western Digital WD800, but I haven’t taken apart many (any?) 2.5″ laptop drives. There used to be a significant price premium for laptop components, an extra cost that I didn’t need to pay for my own needs. This started changing a few years ago: increasing power efficiency requirements and benefits of miniaturization meant small and power efficient components no longer demand a huge price increase, and nowadays laptops outsell desktops. Also, dropping prices of flash memory solid-state drives meant a lot of laptop-sized 2.5″ hard drives got replaced. With terabyte SSDs available for well under a hundred bucks, I can’t think of any reason why I’d ever want to use a 250GB laptop sized hard drive again, so I’m taking apart this Toshiba HDD2D90.

On the bottom I see four wires going into the spindle motor, which I now know to be a brushless motor with “Wye” style winding.

I don’t see an easy way to tap into motor wires while running, so I’m going to skip the oscilloscope examination for this drive.

Closest to the motor control contacts is a chip with Texas Instruments logo and text 7CCN5NTA G4 TLS2502.

Chip with largest surface area was set at an angle relative to everything else. I don’t recognize the logo offhand, but a brief search with PSC acronym found Taiwan-based Powerchip Semiconductor Corp and a matching logo. I didn’t find an exact match for text A2V64S40CTP 747AFD1N but similar model numbers designated memory chips.

Spansion was acquired by Cypress Semiconductor which was itself acquired by Infineon Technologies. After multiple mergers, it was pretty hopeless trying to find details on a FL040A005 74699043. But Spansion’s main product line were flash memory, so this is probably a chunk of flash holding configuration, calibration, and drive-specific information such as remapping of bad blocks.

In between the DRAM candidate and flash memory candidate is a large chip with an old Marvell logo and text 8816717-TFJ1 FT15241.2 0747 C0P TW

My failure to find much of any information on the above chips were disappointing, but at this point no longer surprising. I continued onward to mechanical disassembly.

Western Digital WD800 Mechanical Bits

I looked over the control circuit board for a Western Digital WD800 hard drive and failed to find any documentation relating to chips I found onboard. Oh well. Maybe I’ll have better luck with another drive. For this drive, I continue on to familiar territory: take it apart to marvel at all those mechanical wonders within. As a side effect, this will also make all data stored on this drive functionally inaccessible.

The only tricky part with disassembly is that two of the Torx screws holding lid in place were hidden under the label sticker.

Inside we see a single platter. I’m pretty sure 2002 was recent enough for multi-platter drives, which would mean 80GB was not the highest capacity model in this product line even when it was new.

A translucent yellow bracket limits possible range of motion with read-write head. A small magnet is embedded on one end, but I don’t know its design intent. Perhaps it held the head in place when there’s no power? This bracket is held by a single screw and had to be removed before the read-write head can pivot far enough to clear the platter.

Visible in this picture under the read-write head voice coil is one of two very powerful magnets buried inside this hard drive, the other one is mirror-image on top and already removed in this picture. I have yet to figure out how to nicely separate the magnets from the thick steel cage they are glued(?) to.

Once cleared I could remove the read-write head and platter. There was a pleasant surprise when the platters were removed: I saw three more screws holding the motor in place. Previous HDD teardowns found motors press-fit into the aluminum and impractical to remove. This was the first brushless hard drive motor spindle I could easily remove and store away for potential future projects. Learning more about brushless DC motors is on my to-do list, and I will need motors to experiment with.

This is just the latest in a series of desktop-sized 3.5″ HDD I’ve taken apart. What I haven’t done much of is taking apart their laptop-sized counterpart 2.5″ HDD.

Hard Drive (WD800) Control Board

Putting a hard drive spindle motor’s control signals under an oscilloscope was instructive, even if I don’t yet understand everything that’s going on. Perhaps I could find some documentation to demystify the magic? I looked for hints on the hard drive control circuit board, which told us this 80GB drive dated from 2002 via “WDC (C) 2002” printed in the lower-left corner.

Motor control wires led to this chip, which has a ST Microelectronics logo. Unfortunately, putting these visible identifiers “L6278 17E H99SF0335” into ST.com site search came up empty. Either my search skills are pathetic, ST website database doesn’t go back that far, or this chip is something ST made exclusively for Western Digital under a proprietary contract. What’s certain is that I’m not going to learn more about this particular brushless motor controller. Oh well, I’ll continue my sightseeing tour.

Next chip over has a Marvell logo. And just like the ST chip, searching for “88C5540-LFE G472261.2 0339 B2S” came up empty.

Infineon TLE4417 is not listed on their own web site, but other sites (mostly trying to sell me some chips) say it is a voltage regulator.

If true, it makes sense to have voltage regulation close to the main controller: a WDC WD70C22.

A controller needs some working memory, which is where this Samsung K4S161622E-TC60 DRAM chip comes in.

I didn’t learn very much on this pass, but as I learn more about electronics, I hope future examinations will be more instructive and less of a just-for-fun sightseeing tour like this one. That is yet to be seen, in the meantime I retread familiar ground to take apart this hard drive’s mechanical components.

[UPDATE: Sprite took a stab at hard drive controller hacking some time back. Lack of datasheet documentation was a deal-breaking barrier for me, but not for the experienced hardware hacker.]

Fantom Drives USB Storage (FDU80) Teardown

After wrapping up my adventures in Xbox One SSD upgrades, I decided to stay on the theme of storage devices and dug up this old thing from my pile of hardware awaiting teardown.

This device looks ancient but Fantom Drives appears to be still around today. Or possibly a company has acquired rights to that name and logo for doing business. The website lists a few internal M.2 SSDs but most of the product line are external USB storage drives. This is likely an early product of that line.

Size of this enclosure is consistent with a single 5.25″ floppy (or CD-ROM or DVD) drive bay. However, the front faceplate is empty with no slot for a disk.

Around the back we see a plug (IEC 60320 C13/C14) for power and a USB plug (type B) for data. A power switch and cooling fan rounds out the plate. I found the fan curious, because I don’t see any grille for intake or exhaust on this enclosure. Airflow would have been limited at best.

I see four screws on this plate. Two of them holds the fan in place, and the other two probably holds the USB data translation system in place. Neither look like a way for me to open up the box.

Four screws are visible on the bottom, and again they don’t look like something that’ll let me open the enclosure. They probably hold the storage device within.

I’m sure the warranty is long gone on this device, but I’m thankful for this “Warranty Void if This Seal is Broken” sticker because they would have placed it in a location critical to disassembly. Which is where I should start.

After the sticker was removed, the dark plastic clips on either side could be removed, allowing top and bottom enclosure halves to separate. Inside the enclosure we see… a standard 3.5″ hard disk drive looking pretty small inside that enclosure. It has a capacity of 80GB, giving an idea of how old this thing is. Nowadays we can buy cheap microSD cards with more capacity.

Another hint of its age is the antiquated parallel ATA interface used by this drive. I remember working on old PCs, fighting these huge and unwieldy cables. I do not miss them. Modern SATA (serial ATA) is so much easier to work with.

The spindle motor on this hard drive caught my attention: it is connected with four wires and not three like the hard drive motor I tried to turn into a generator. Could this be a pair of windings for two independent sets of coils? If so, I might try to run this thing using a stepper motor driver just to see what happens.

As for the electronics, I don’t know if I will ever find use for a board that translates between USB2 and PATA, two old and slow interfaces. The power supply is more likely to find reuse. I have a sizable stockpile of wall warts including several units with 12V DC output and several with 5V DC output. However, this particular power supply might come in handy if I ever need 12V and 5V together.

But back to that four-wire motor: what’s going on over those wires?

Looking Inside GMKtec NucBox3

I thought the GMKtec NucBox3 looked interesting (at least on paper) as candidate ROS brain, so I ordered one (*) for a closer look despite some skepticism. All pictures on that Amazon listing look perfect, I suspected they were all 3D computer renders instead of photos of an actual product. There’s a chance the actual product looked very different from the listing.

The good news: the product is real and for the most part, as depicted in the listing. I find good fit and finish on its plastic enclosure. There is one downside: fingerprints show up very clearly. I had to wipe down the case pretty aggressively for these pictures and I still see greasy smudges. Well, at least you know these aren’t renders! One instance where oily fingerprint smudges are a feature, not a bug.

I see two brass heat-set inserts on the bottom of the case which will be useful for mounting this little box somewhere. They look very small but this is a small lightweight box so it would probably suffice.

Here we also see where actual product differed from product listing rendering. The company website page for NucBox3 showed an access panel to upgrade memory or storage.

But there’s no such access panel on the real thing, and it’s not clear how to get inside without one. Documents in the box consisted of a minimal warranty card in the box and no instruction manual. No matter, the lack of a convenient access panel or a manual shall not deter me from getting inside for a look.

Hiding fasteners under glued-on rubber feet is a common and effective technique. These four fasteners are not symmetrical so, even though the box is a square, we need to remember correct orientation to reinstall.

Without a convenient access door for upgrades, I wasn’t sure what else would differ from listing picture. I was afraid memory and storage would be soldered-in parts, but I was relieved to find they were standard DDR4 RAM and M.2 2280 SSD as advertised. They’re just a tiny bit harder to access without the panel.

Judging by its M.2 keys, we have the option to upgrade this factory-installed SATA M.2 SSD to a higher-performing NVMe M.2 SSD if needed.

What appears to be empty threaded holes (marked with circles) are actually used to secure the CPU heatsink from the other side. (There’s a fourth one under RAM module and not visible in this image.) Four fasteners (marked with squares) secure the motherboard and must be removed to proceed.

The headphone jack protrudes into the enclosure, so we must tilt the mainboard from the opposite side for removal. But we have to be careful because we are limited by length of WiFi antenna wires.

A block of foam keeps WiFi antenna connectors in place, peeling it back allowed the connectors to be released. The antennae themselves appear to be thin sheets glued to the top of the case, similar to what I’ve salvaged from laptops. How securely were they held? I don’t know. I didn’t try to peel them off.

Freed of WiFi wires, I could flip the mainboard over to see a big heatsink surrounded by connectors. As chock-full of connectors as this product already is, I was surprised to see that there are still several provisions for even more connectors on the circuit board. I’m also very fascinated by connectors used here for USB3, HDMI, and DisplayPort. I usually see them oriented flat against the circuit board as typical of laptop mainboards, but without design pressure to be thin, these connectors are standing upright. This is a tradeoff to fit more connectors on the edge of a circuit board, but each connector must go deeper to obtain the necessary mechanical strength to withstand use.

Looking in from the side, the heatsink appears to have a flat bottom. This is good news if I want to mount a different heatsink on this board, possibly with a fan. The flat bottom means I don’t have to worry about sticking out to make thermal contact with other chips or have to cut a hole to clear protrusions. If I want to mount to the same holes, I will have to drill four holes which unfortunately are irregularly spaced but not an insurmountable challenge. All that said, I’m more likely to just point a fan at this heatsink if heat proves to be a problem.

Using this computer as robot brain also means running it on battery power. Nominal power requirements are listed as 12V up to 3A. My voltmeter measured the factory power adapter output at 12.27V. But what can this thing tolerate? I found this chip directly behind the DC power barrel jack, but a search for DC3905 WK1MEG (or WX1MEG) didn’t turn up anything definitive. Texas Instruments has a LP3905 and Analog inherited Linear Technology’s LT3905. Both chips are designed for DC power handling, but neither footprint matches this chip. This might not even be the power management chip, I’m only guessing based on its proximity to the DC barrel jack.

As far as I know, the highest voltage requirement on this PC are USB ports at 5V. On the assumption that nothing on this machine actually needs 12V, then all power conversion are buck converters to lower voltage levels. If true, then this little box should be OK running directly on 3S LiPo power (Three lithium-polymer battery cells in series) which would range from 12.6V fully charged to 11.1V nominal to 10V low power cutoff. I’ll use the power brick that came in the box to verify everything works before testing my battery power hypothesis.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Seagate Backup+ Hub External Drive 8TB (SRD0PV1) Teardown

I’ve owned and taken apart several USB external hard drives to extract their standard form factor SATA hard drive within. Today another drive shall undergo an extraction process. This is a Seagate Backup Plus Hub (SRD0PV1) I had used to back up my TrueNAS disk array. I used a Raspberry Pi as TrueNAS replication host and this drive as storage. I paid a few extra bucks for the version with an integrated USB hub hoping to power my Raspberry Pi from one of the ports and simplify my wiring. Unfortunately, I learned that when the drive initially spins up, all power goes to the drive and these USB ports become momentarily disconnected. Shutting down the Pi sank my plan. I shrugged, chalked the few extra bucks to lesson learned and ignored its integrated USB ports. I powered my Pi conventionally and used the drive for TrueNAS replication back up storage. That daily backup setup worked for about two years before TrueNAS started reporting replication failures: “Device not found.” Where did it go? Looks like my Raspberry Pi would acknowledge the drive existed as a USB device but couldn’t use it as one.

Running Ubuntu’s dmesg command and querying for all the lines that have USB in it, I found a trail ending with an error message “Cannot enable. Maybe the USB cable is bad?” Following that advice, I tried several different cables but that didn’t make a difference, so it wasn’t the cable. I tried plugging the drive into my Windows machine with similar results: New USB device? Yes. New hard drive? No.

Thus it was time for another hard drive shucking session. Since my TrueNAS array is running well, the data within isn’t critical right now. But it’s a low-pressure opportunity to learn if my data backup would survive such an episode of hardware failure.

I found no external fasteners (not even under its rubber feet) so I started attacking visible seams with iFixit opening pick and opening tool.

After a symphony of snapping sounds announcing death of many plastic clips, top lid came free. We can see a Seagate BarraCuda 3.5″ HDD. It is from their “Compute” product line for general personal storage usage. Usually with a two-year warranty, so we’re right on time.

Speaking of warranty, there was an interesting piece of text on the label that I don’t think I’ve seen elsewhere before. “HDD sold as component of OEM solution and not for resale. The product warranty does not cover HDD if removed from OEM solution.” If the warranty hadn’t already expired, I guess I’ve just voided it.

Many more snapping of clips later, the external enclosure has been separated into three plastic pieces: top, bottom, and a frame sandwiched between them.

RIP, plastic clips.

Vibration dampening rubber knobs sit between the external frame and screws fastening the HDD to a folded sheet metal tray.

Once those screws were removed, the drive could be slid off the tray. I was surprised to see such a large expanse of circuit board; I had expected two small boards with a ribbon cable to bridge them.

Removing two screws allowed the circuit board to be removed. All physical connectors (SATA, power, USB) are on this side, as are a few through-hole electrolytic capacitors.

The other side is sparsely populated with surface-mount components.

I didn’t see any visible signs of damage that might explain why Ubuntu “cannot enable” this device. Not that I would necessarily know how to fix it, anyway. This was just for curiosity. I might as well look around now that I have this in my hands.

I noticed three identical copies of a circuit, but beyond that, I don’t know what it does. Why would the circuit board for an external hard drive need three of something?

The largest chip on this board is a GL3520 by Genesys Logic, a Taiwan company specializing in USB solutions. The GL3520 is no longer listed on their website, but their GL3523 (which I infer to be its successor based on model number) is listed as a USB3 hub controller. This is consistent with integrated USB hub functionality.

The next largest chip is the ASM1153 by ASMedia, another Taiwan company. ASM1153 is a USB to SATA bridge and its presence is completely expected within an external USB hard drive product.

But now with the enclosure removed, this Seagate BarraCuda Compute 8TB drive has been transferred to the PC with a Rosewill hard disk drive cage so it is now an internal drive. It was successfully detected as a SATA device, and by running “zpool import” I was able to mount it to my Ubuntu filesystem. I copied a few files as tests, and they all seemed intact. Then I ran “zpool scrub“, and no errors were detected. I take this to mean that my data has survived which is great news. I want to keep using it as my TrueNAS replication backup, but I don’t want to dedicate my PC tower to this task. Fortunately, I have an old Dell Optiplex 960 that should suit.

Extracted Magnets from Broken iPad Case

This was an aftermarket protective cover case designed to fit 6th generation Apple iPad tablets. Purchased from the lowest bidder on Amazon that day (*) it did its job for several years absorbing abuse until a corner broke off and the case could no longer latch in place. It turned out a case that wouldn’t stay attached was worse than no case at all, as the iPad fell out causing a dent on the back.

While remaining three corners of this case were still attached, they all showed cracks in the plastic. Thus it was retired and replaced with a new case. Before this broken case is sent to landfill, though, I wanted to salvage its embedded magnets. This cover has the option to fold into a stand, held in shape by magnets. Closing the cover is also something detectable by the iPad, so there’s a Hall sensor inside the tablet picking up a precisely located magnet.

Using a screwdriver for its steel shaft, I could feel tugs at several locations indicating a magnet. Given how thin they must be, I expected to find a few tiny slivers of rare-earth magnets. And given the thin fabric construction, I decided to start by cutting an edge with scissors.

First magnet was quickly uncovered.

Pulling on the glued-on fabric, I uncovered the remaining magnets embedded within the first panel. Four small rectangular magnets near the middle of the edge. Surrounded by two larger rectangular magnets on either side. There’s a circular magnet as well, away from the rest. I had only expected one or two magnets, so this is an unexpected bounty.

The magnets weren’t attached to the yellow plastic backing at all, merely held in place by adhesive on either side. They could be peeled off with minimal residue. This is working out really well.

Continued peeling discovered another circular magnet in the middle panel, and another set of rectangular magnets on the third panel that matched the arrangement of magnets in the first panel. Those two arrays of rectangular magnets on outermost edges would implement the fold-into-a-stand function. The two circular magnets don’t line up to each other, I guess they are there for iPad “cover is closed” detection.

I cut into this cover expecting just a magnet or two, so I’m very happy I came out with a stack of 18 little magnets. They are very thin so it should be easy to fit them into places in future projects. In fact, they are so thin I need to worry about protecting them. This material is brittle: I broke that topmost magnet in half when peeling it off the adhesive layer, a lesson warning me to be careful with the rest.

(*) Disclosure: As an Amazon Associate I earn from qualifying purchases.

Monoprice 30W Powered Desktop Speakers (605300)

Encouraged by my resurrected Insignia powered subwoofer, I dug up another item from my to-do list. These are Monoprice Pro Audio Series 30W Powered Portable Speakers, item #605300. (No product link as this item has long since been discontinued, though their Powered Desktop Speakers category is still alive and well.) I had bought it for use as my computer desktop speakers and they worked well for a few years before falling silent. Then they sat for many more years in the teardown/repair pile until now.

The two speakers are not symmetrical. One of them have all the equipment and the other is a simple box with drivers. The fancier box (wired up to be the right channel but shown to the left in above picture) has a volume knob and two audio jacks. One jack is an auxiliary input to temporarily replace signals coming in from rear main audio input, and the other a headphone jack we can plug in to temporarily listen to something privately. This latter jack still works: I could hear the audio signal through headphones plugged into this jack, and I can hear loudness changing as I turn the volume knob.

The asymmetry is very visible when looking at the rear of both speakers. One has the power plug and switch, plus the aforementioned main audio input. A slider switch for “Bass Boost” On/Off (I never noticed much of a difference either way) and speaker level output to drive the other speaker.

The volume knob is surrounded by a ring of plastic that glows blue when it is powered on. This light still illuminates, so I don’t think the problem is as simple as a blown fuse.

Looking inside the simpler box first, it’s hard to see very much through the small opening. The electronic bits we could see is probably an audio crossover circuit.

Moving on to the other speaker, we see a lot more and thankfully they’re more accessible as well. AC power enters the enclosure to an in-line fuse. (I didn’t think the fuse was the problem, but I checked anyway and there is indeed electrical continuity.) Power then flows to a transformer which steps ~120V AC down to ~14V AC. This stepped-down voltage connects to the circuit board, adjacent to a large four-pin package that looks like a rectifier.

Four sets of wires lead from this board into the speaker enclosure. The smallest and thinnest pair of wires go to the smaller speaker driver for higher frequencies, and the thicker pair goes to the larger driver. Two gray bundles lead to front-panel controls, one for the volume knob/power LED and the other for the auxiliary/headphone jacks.

Examining the circuit board, I see discoloration underneath these two components. Labeled Z1 and Z2 with diode symbols, I infer these are Zener diodes. Z2 was held down by a white-colored compound of unknown nature. That stuff was tenacious and refused to peel off, but I could cut it with a knife allowing me to unsolder both Z1 and Z2. Once removed I could read diode markings as IN4742A, confirming they are Zener diodes. I don’t have any replacements on hand, but I could give these two a quick basic test. With my multimeter switched to diode test mode, they read ~0.72V the one way and nothing the other. These are expected values of a diode proving they have neither failed open nor failed short. Circuit board discoloration showed that they’ve been running hot, but that fact by itself is not necessarily a problem with Zener diodes. A full diode test is beyond my abilities at the moment, so I soldered them back into the board and tested the speaker again. I had a slim hope that heat stress damaged a solder joint and resoldering them would bring the speaker back to life. No such luck, but it was easy to check.

Next, I looked into the still-functioning headphone jack. The speakers would go silent when audio is going through the headphones. Perhaps the jack is stuck in the “we have headphones” configuration. This would keep the speakers silent even when there are no headphones present. Unfortunately, the audio jacks are mounted on this circuit board, glued to the enclosure. Breaking the board free may be destructive, so I put this off to later.

Looking for promising components to investigate, I settled on the audio amplifier chip. It is a big component with large pins that I could probe, and its markings are visible for easy identification. I found and downloaded the datasheet for ST Electronics TDA7265 (25+25W Stereo Amplifier with Mute & Stand-By) and got to work understanding how it was used here.

I printed out a picture of the circuit board (*) so I could take notes as I probed the board (with the power off) while comparing it to TDA7265 datasheet information. The first order of business was looking for pins 1 and 6, which the datasheet said were both negative side of input power. I found those two pins connected to the same copper trace on the board leading to one pin of the rectifier, giving me confidence that I’m looking at the right part and I am oriented in the correct direction. I noted the pins I wanted to check once I’ve powered on the board:

  • Pins labeled R+ and R- should be DC power rectified from the ~14V AC transformer output. If there’s no voltage, I may have a dead rectifier.
  • There are two inputs, each with their positive and negative pins. I’m not sure which is wired as left and which is right, but I can connect a stereo signal to both input jacks. I should see line level voltage if audio signal makes it to the amplifier chip. If not, I can backtrack from here.
  • If audio makes it to input, I will probe Outputs 1 and 2, which should have speaker level voltage relative to a shared ground.
  • If there is input signal but no output, I will probe pin 5 which controls mute & standby behavior. See what voltages I read, and compare behavior to what datasheet says.

With this plan in hand, I prepared my tools. My LRWave web app written earlier for Lissajous experiments will provide test input signal. For probing the circuit, I have my multimeter and I have my oscilloscope. As a quick test, with the power still off I probed the audio input jacks while LRWave was running full blast. I measured ~0.6V AC on those pins (in the above photo, labeled in the lower right as “R IN, R GND, L IN, and L GND”.) This is a great start. I then turned on the power strip (powering up the speaker) and was immediately blasted by the sound of LRWave’s 440Hz sine wave.

The speaker works now! That is great, but… why does it work now? The last hardware modification I deliberately made to the device was to resolder Zener diodes Z1 and Z2. I tested the speakers then, and it didn’t make any sound. I must have made another (non-deliberate) change to the hardware to bring it back to life. Was it reaching for the audio jacks and jiggling a loose cable connection? Was it something I did by accident while probing the amplifier chip circuit? I don’t know. The speaker works again, but this success was unsatisfying. I wouldn’t call it “repaired”, either, as I can’t explain how I fixed it. It could just as easily and mysteriously break again tomorrow. But if it does, at least I have a plan to investigate for Round 2.

(*) The lone surface mount IC visible on this side is a ST TL074 quad op-amp.

Hamilton Beach Coffee Grinder (Type CM04 Model 80344)

The coffee drinker of the house has upgraded to a burr-type grinder for coffee beans, retiring this well-used unit which is now on the teardown bench.

It’s more accurately a coffee bean chopper, since it spins a set of blades to break them apart.

Cracks have started developing on its blade hub, which might be related to why one of the two blade tips drag on the bowl carving a channel. (Slightly out of focus in above picture.)

Mechanically, I’m curious to see implementation details for the cord management system built into the base. I expect the rest of the machine to be a shell around an AC motor spinning the blade.

I peeled off three rubber feet expecting to find fasteners hidden underneath, but there was nothing.

The base was actually held in place by a plastic retaining mechanism in the center. After popping off its smooth cosmetic cover, we could grasp the retainer to unlock it with a twist. Then the retainer could be removed, which released the base.

Power cord reel is visible after base was removed.

This little piece of plastic towards the end stops power cord from unwinding further, bumping up against a retaining ring. This retaining ring is held in place by four hooks. Gripping the ring with pliers and twisting clockwise a few degrees to slide past the hooks allowing removal of ring and power cord reel.

I was surprised to find a slip-ring style arrangement of metal rings and fingers. I had expected to see a very clever arrangement of bent and creatively routed wires to support power cord reel rotation without the parts count and complexity of a slip ring. I was wrong: it’s a slip ring.

Underneath the slip ring we see the first (and it turns out, the only) signs of traditional fasteners. Three Philips-head fasteners around the outside keep the motor frame in place.

What looks like a flat-head fastener in the middle is actually the motor shaft.

Putting a flat-head screwdriver on the motor shaft allows us to control its rotation and remove the blade. After blade removal, the motor could be maneuvered out the bottom.

With the motor out of the way, we could pry on plastic clips holding top ring in place. This one shows several scars from my efforts to release it.

With the ring removed, the control circuit slides out the top.

I had not noticed the safety interlock switch until I saw wires leading up to it. This ensures the lid must be in place before the blades would spin. It’s pretty clogged with coffee grounds which will eventually cause it to become unreliable.

The heart of the machine is a motor with the following printed on it:

120V 60Hz

A web search found Hondaraya Engineering is a Hong Kong company, small enough of an operation that web search engines helpfully suggested I probably meant Honda the Japanese manufacturing giant. I wonder if Hondaraya was responsible for just the motor or if they were contracted by Hamilton Beach to engineer the entire grinder.

I was impressed by how this machine was designed. At its core, a pretty simple machine: a motor spinning a blade. The design and engineering team nevertheless devised a compact cord management system at the bottom. And it was held together almost entirely by cleverly designed plastic retaining mechanisms, the only exception were the three screws holding the motor frame in place. The lack of glue should mean easy assembly and repair, though replacement parts are not sold for this device. I never did find a good explanation why one blade tip has been dragging on the bowl. If a replacement blade were available, it would have been easy to replace and test to see if that would address the problem.

Capacitor Replacement on Insignia 100W Powered Subwoofer (NS-RSW211)

My home theater had a small powered subwoofer, an Insignia NS-RSW211 Rocketboost 6-1/2″ 70W Wired/Wireless-Ready Subwoofer. After several years of use, it started exhibiting some strange effects and I disconnected it. Since I’m not a huge home theater buff and it was a modest unit to begin with, I didn’t really miss its absence. It sat forgotten in a corner until I saw Monoprice held a sale on their item #8248, a similar-sized powered subwoofer that would be a great replacement. Before I hit “Buy” on the Monoprice item, though, I thought I should make an effort to fix the one I have.

The failing symptoms indicate an intermittent connection somewhere in the system. When I turn on the subwoofer, it is fine for the first few minutes. After that initial period, sound would start cutting in and out at irregular periods. Every time it cuts out, the low bass sounds disappear. When it cuts back in, a deep “thump” announces return of low frequencies. This would start out tolerably infrequent, like hearing a distant firework show. Interruptions then become increasingly frequent. Eventually it will sound like automatic weapons fire in the background even when we’re not watching an action film, at which point I would turn it off. After a few hours of rest, I could repeat the cycle. Intermittent issues are always annoying to diagnose (part of why I’ve been putting it off) but I should at least take a look. On to the workbench it goes!

There are a lot of fasteners visible on this back plate. This is not a huge surprise: a subwoofer’s job is to push those low frequency thumps. Each thump will rattle anything not securely fastened, and every thump will be trying to loosen every fastener. In fact, the large numbers of fasteners are quite welcome: if it had been glued together, opening it up would be a destructive act making a successful repair unlikely.

But it wasn’t glued, so I could get to work. Removing the outermost eight fasteners allowed me to remove the rear module. I was a little surprised to see all electronics were sealed inside an airtight box. This might be good for acoustics but bad for air cooling circulation. The only thing poking into the acoustic chamber are the pair of speaker wires going to the driver itself. They used commodity spade connectors and were easy to disconnect so I could focus on the electronics box.

Removing the next outermost set of six fasteners allowed me to open up the electronics box. I was greeted with the thick stench of fried electronics. Something definitely died in here and, if it smelled this strong, I should be able to see it.

Yep, there it is. Capacitor C28 is toast. Finding this dead capacitor is good news, much easier than diagnosing an intermittent issue. The bad news is I’m not familiar enough with power supply theory of operation to explain why this absolutely and completely dead capacitor would cause an intermittent failure.

One end has completely blackened and appears to have broken open as well.

The yellow circuit board appears to be the power supply subsystem. 120V AC power cable (black & white wires) goes to the power switch, then into one corner of this yellow board near the dead capacitor. Diagonally opposite them is this connector delivering +24V to the rest of the subwoofer.

Unplugging AC input and DC output wires, then removing four screws, allowed removal of this power supply board so I could unsolder the dead capacitor easily. It came off in two separate pieces, very dead.

Reading markings on the charred capacitor carcass was a challenge. After playing with lighting, camera settings, and photo editing, I could make it out as:


I’m not familiar with this type of capacitor and didn’t know how to interpret those numbers. Looking around online, I found this page which said “105” meant 10 * 105 pF = 1000000 pF = 1000 nF = 1 uF and the “K” meant +/- 10% tolerance. The voltage rating portion didn’t line up with anything on that page, though. I’m inferring that “250KC” means something that can handle up to at least 250V, as this device can take up to 230V AC input.

Looking around my various assortment trays of capacitors, I didn’t find anything +/- 10% of 1uF. I then looked through my pile of teardown remnants for capacitors to salvage. The closest candidate was a 0.68uF 450V capacitor from the Antec power supply that caught on fire.

It even had the same footprint as the original toasted capacitor, making for an easy fit in the available space. However, 0.68uF is still short of the capacitance of the original so I continued looking.

I found a 0.22uF 250V capacitor inside the surprisingly complex evaporator fan. There was a clear conformal coating over everything that made removal a bit of a pain (and the result looking messy.) But they gave me a theoretical 0.68uF + 0.22uF = 0.90uF and my multimeter says they’re actually a tiny bit above rated value. Bringing me within 10% of 1uF, good enough for a test run.

Since the original capacitor slot was already occupied by the 0.68uF capacitor, the second parallel capacitor had to sit on the back.

I buttoned everything back up and preliminary test looks promising. After playing through a two-hour movie, I have yet to hear the thumping “fireworks” to “gunfire” failure sequence. Still unknown: what killed the original capacitor, and whether the same will happen to these replacements. Time will tell. In the meantime, I’ve managed to keep something out of landfill and resisted the temptation to buy a Monoprice powered subwoofer on sale. I’m thankful the design & engineering team built this device in a repairable way.

High Power 600W Power Supply (HP1-J600GD-F12S)

Along with the “keyboard is broken” laptop, I was also asked to look into a mid-tower PC that would no longer turn on. I grabbed a power supply I had on hand and plugged it into the motherboard, which happily powered up. Diagnosis: dead power supply. I bought a new power supply for the PC to bring it back to life, now it’s time to take apart the dead power supply to see if I can find anything interesting. Could it be as easy as a popped circuit breaker or a blown fuse?

According to the label, the manufacturer has the impossibly unsearchable name of “High Power”. Fortunately, the model number HP1-J600GD-F12S is specific enough to find a product page on the manufacturer’s site. The exact model string also returned a hit for a power supply under Newegg’s house brand Rosewill, implying the same device was sold under Newegg’s own name. Amusingly, Newegg’s Rosewill product listing included pictures with “High Power” embossed on the side.

If there is a user-replaceable fuse or a user-accessible circuit breaker, they should be adjacent to the power socket and switch. I saw nothing promising at the expected location or anywhere else along the exterior.

Which meant it was time to void the warranty.

Exterior enclosure consisted of two pieces of sheet metal each bent into a U shape and held together with four fasteners. Once pried apart, I had to cut a few more zip-ties holding the cooling fan power wire in place before I could unplug it to get a clear view at the interior. Everything looks clean. In fact, it looked too clean — either this computer hadn’t been used very much before it blew, or it lived in a location with good air filtration to remove dust.

Still on the hunt for a circuit breaker or a fuse, I found the standard boilerplate fuse replacement warning. Usually, this kind of language would be printed immediately adjacent to a user-serviceable fuse. But getting here required breaking the warranty seal and none of the adjacent components looked like a fuse to me.

Disassembly continued until I could see the circuit traces at the bottom of the board. Getting here required some destructive cutting of wires, so there’s no bringing this thing back online. Perhaps someone with better skills could get here nondestructively but I lacked the skill or the motivation to figure things out nicely. I saw no obviously damaged components or traces on this side, either. But more importantly, now I could see that 120V AC line voltage input wire is connected to a single wire. That must lead to the fuse.

Turning the board back over, I see the line voltage input wire (brown) connected to a black wire that led to a cylinder covered in heat-shrink tubing and held in place by black epoxy. The shape of that cylinder is consistent with a fuse. The heat-shrink and epoxy meant this is really not intended to be easily replaced.

Once unsoldered, I could see the electronic schematic symbol for fuse printed on the circuit board. The “F” in its designation “F1” is consistent with “Fuse”, as do the amperage/voltage ratings listed below. This fuse is a few centimeters away from the caution message I noticed earlier, which was farther away than I had expected. My multi-meter showed no continuity across this device, so indeed the fuse has blown. I cut off the heat-shrink hoping to see a burnt filament inside a glass tube, but this fuse didn’t use a glass tube.

I started this teardown wondering if it was “as easy as a popped circuit breaker or a blown fuse”. While it was indeed a blown fuse, a nondestructive replacement would not have been easy. I don’t know why the fuse on this device was designed to be so difficult to access and replace, but I appreciate it is far better to blow a fuse than for a failing power supply to start a fire.

Zalman 120mm Case Fan, Clear with Blue LED (ZA1225CSL)

After years of faithful service, this particular cooling fan has worn down to a point where it would vibrate noisily, its associated friction dragging down fan blade speed. Time for me to retire it but not before subjecting it to a teardown.

Sticker on the back says it is a Zalman model ZA1225CSL.

This particular fan was cast in clear plastic and has embedded blue LEDs for visual novelty.

Four LEDs are angled such that they turn fan blades into LED light pipes creating an illuminated arc while the fan spun.

A glued-on clear cover hides the LED within. Getting good leverage on this cover is tough with the fan blades in place, so I’ll work on removing the fan first.

A razor blade made quick work of the rear sticker.

Under the sticker, we can see fan motor shaft held in place by a small white plastic ring.

Remove the ring (not terribly visible against a white background, I admit) and the fan hub slides free. Despite the racket it has been making, I see no obvious signs of wear on either this fan hub shaft or the hub bearing. I guess a tiny amount of wear was enough for the system to start wobbling.

It was easy to break those LED covers free once fan blades were no longer in the way.

The blue LEDs appear to be standard 3mm diameter units, powered by wires that were glued into channels molded into fan hub support beams. Pulling them free destroyed the clear insulation on those wires. Given how affordable LEDs are now, there’s not much point trying to salvage these LEDs beyond trying to see if I could. I had a 75% success rate: one LED out of four was torn off its wires, oops.

I removed the fan hub, and it appears this chip is in charge of the operation. Marked FTC S276.2QD, a web search found this to be the FS276 two-phase DC motor control chip by FTC. The website indicates Feeling Technology Corp is a Taiwan-based semiconductor company. The chip’s datasheet shows an integrated hall effect sensor, which explains why it is positioned to pick up magnetic field of the fan rotor. It has four pins: power on one end, ground on the other, and sinks for two motor phases.

The single-sided circuit board marked ZB111228 implemented the FS276 datasheet circuit with a few additions. Around the perimeter, we have pads for the four blue LEDs, each connected to power and ground through a current-limiting resistor marked with 681. I believe this means 68 * 101 = 680 ohms. We also have a transistor, connected to one of the two motor phases, to communicate tachometer signal.

I will likely find a use for the three-conductor wire with PC cooling fan connector on one end. I might stick the blue LEDs on a future project just for laughs. The motor control circuit board will go to electronic recycle. All the clear plastic will go to landfill.

MageGee Wireless Keyboard (TS92)

In the interest of improving ergonomics, I’ve been experimenting with different keyboard placements. I have some ideas about attaching keyboard to my chair instead of my desk, and a wireless keyboard would eliminate concerns about routing wires. Especially wires that could get pinched or rolled over when I move my chair. Since this is just a starting point for experimentation, I wanted something I could feel free to modify as ideas may strike. I looked for the cheapest and smallest wireless keyboard and found the MageGee TS92 Wireless Keyboard (Pink). (*)

This is a “60% keyboard” which is a phrase I’ve seen used two different ways. The first refers to physical size of individual keys, if they were smaller than those on a standard keyboard. The second way refers to the overall keyboard with fewer keys than the standard keyboard, but individual keys are still the same size as those on a standard keyboard. This is the latter: elimination of numeric keypad, arrow keys, etc. means this keyboard only has 61 keys, roughly 60% of standard keyboards which typically have 101 keys. But each key is still the normal size.

The lettering on these keys are… sufficient. Edges are blurry and not very crisp, and consistency varies. But the labels are readable so it’s fine. The length of travel on these keys are pretty good, much longer than a typical laptop keyboard, but the tactile feedback is poor. Consistent with cheap membrane keyboards, which of course this is.

Back side of the keyboard shows a nice touch: a slot to store the wireless USB dongle so it doesn’t get lost. There is also an on/off switch and, next to it, a USB Type-C port (not visible in picture, facing away from camera) for charging the onboard battery.

Looks pretty simple and straightforward, let’s open it up to see what’s inside.

I peeled off everything held with adhesives expecting some fasteners to be hidden underneath. I was surprised to find nothing. Is this thing glued together? Or held with clips?

I found my answer when I discovered that this thing had RGB LEDs. I did not intend to buy a light-up keyboard, but I have one now. The illumination showed screws hiding under keys.

There are six Philips-head self-tapping plastic screws hidden under keys distributed around the keyboard.

Once they were removed, keys assembly easily lifted away to expose the membrane underneath.

Underneath the membrane is the light-up subassembly. Looks like a row of LEDs across the top that shines onto a clear plastic sheet acting to diffuse and direct their light.

I count five LEDs, and the bumps molded into clear plastic sheet worked well to direct light where the keys are.

I had expected to see a single data wire consistent with NeoPixel a.k.a. WS2812 style of individually addressable RGB LEDs. But label of SCL and SDA implies this LED strip is controlled via I2C. If it were a larger array I would be interested in digging deeper with a logic analyzer, but a strip of just five LEDs isn’t interesting enough to me so I moved on.

Underneath the LED we see the battery, connected to a power control board (which has both the on/off switch and the Type-C charging port) feeding power to the mainboard.

Single cell lithium-polymer battery with claimed 2000mAh capacity.

The power control board is fascinating, because somebody managed to lay everything out on a single layer. Of course, they’re helped by the fact that this particular Type-C connector doesn’t break out all of the pins. Probably just a simple voltage divider requesting 5V, or maybe not even that! I hope that little chip at U1 labeled B5TE (or 85TE) is a real lithium-ion battery manage system (BMS) because I don’t see any other candidates and I don’t want a fiery battery.

The main board has fewer components but more traces, most of which led to the keyboard membrane. There appears to be two chips under blobs of epoxy, and a PCB antenna similar to others I’ve seen designed to work on 2.4GHz.

With easy disassembly and modular construction, I think it’ll be easy to modify this keyboard if ideas should strike. Or if I decide I don’t need a keyboard after all, that power subsystem would be easy (and useful!) for other projects.

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