Amazon Fire SR043KL Backlight Layers

I took apart an Amazon Fire tablet (SR043KL) retired by cracked touch digitizer glass, seeking to salvage its display backlight and I was successful. I am fascinated by the optical behavior of modern LED backlights, even those used in products with a low price target like this tablet. After fussing with light diffusers for my Glow Flow project, I have a great deal of appreciation and respect for how evenly these backlights distributed their LED light.

I had a lot of time invested in the earlier LG laptop backlight project and was timid about fully exploring all its backlight layers, fearing that I would break something. Now that I have a smaller backlight with lower stakes, I’m going to take the layers apart and see how they act and interact with each other.

At first glance the layers for this backlight are arranged slightly differently from the LG laptop backlight. I’m too new into this field to guess what tradeoffs are involved. What I do know is that the bottom-most layer on the Fire backlight appears to be non-removable. When acting alone, I could see a dotted pattern almost like dithering.

Above this layer is a sheet of smooth matte translucent white that I would have expected to be the top layer, but here it is.

When in place, it blended the dotted pattern together into something smoother. I think this looks great as-is, but we have two more layers to make it even better.

The third layer looks wild, with the optical characteristics I associate with Fresnel lenses and lenticular lenses, but this pattern looks different and I wished I knew the right name for it so I could read more about it.

When installed, it imparted a bit of pattern along with a rainbow-like sheen.

The fourth and final layer also has that optical property, but dialed back a bit. It also has a matte top finish similar to the second layer.

When in place, we have our backlight, providing an impressively even illumination across the entire area with all light provided by a row of LEDs on just one edge.

Speaking of those LEDs, I count eighteen of them. Given that they start illuminating at around fifteen Volts, my guess is that we’re looking at three parallel strings of six LEDs each. I don’t have anything to accurately clamp current at 3*20=60mA (my bench power supply current limit is only guaranteed to be +/- 10mA) but I estimate that would be somewhere near eighteen volts which makes this barely over one watt at maximum brightness. Pretty neat!

I’m setting this aside for later use. Emily Velasco has said she has a project idea that might make use of a small backlight, so it might go to her instead. If it does, I’m sure we’ll get something really weird and cool out of it because that’s what Emily builds.

Amazon Fire SR043KL Display Disassembly

I have taken apart an Amazon Fire tablet (SR043KL) and retrieved the prize I sought: an intact display assembly under the cracked digitizer glass. Though presence or absence of cracks in the LCD wouldn’t have mattered for my project anyway. My objective is actually the backlight behind it.

Just like the LG laptop display I disassembled earlier, this display module is held on all edges by thin precision black tape. Peeling back the tape, I had hoped to find a LED backlight driver as I did on the laptop display, but not this time. There are a few small passive components here, but the backlight driver must be on the mainboard hidden under one of those metal shields.

Lacking an easily accessible LED driver, the next objective is to hunt for the backlight LED circuit itself. I expected them to be the largest traces relative to the other components, and I see two exposed contacts already labelled with + and -. Hmm… could it be that easy? I could do a quick test: since these two points were already exposed, soldering some wires to them were straightforward.

In order to see if the LEDs glow, I peeled back more of the tape. Slowly increasing the voltage, I started seeing a glow at around 15V. Wow, it’s really was that easy.

I have no idea how to drive this LCD array, and I have no intention to learn. My objective for today is the LED backlight. So after I peeled away all black tape around the perimeter, I sliced the high density LCD pixel data ribbon in order to separate the two parts.

There isn’t much more to be said about the LCD array. I was able to peel off the polarizer film, this time without cracking any glass, but using acetone to clean off the adhesive once again caused the film to disintegrate. That’s two strikes against acetone, I’ll have to try something else next time.

I have to put more thought into polarizer film recovery, but that’s only a mild distraction from my fascination with the backlight and its sheets of optical magic.

Amazon Fire SR043KL Screen Removal

Tearing down an Amazon Fire tablet retired due to a broken screen, I removed everything I can from the back hoping to find something that would help me release the front. This was unlikely but I held out hope…. hope that has now been dashed. There are no secret back door entrances, I have to fight the double-sided adhesive strips protecting the front door. For me, this is the least enjoyable part of electronics teardowns. There’s no clever puzzle-solving in tearing glued pieces apart, it’s just brute force messy nastiness.

I have not yet developed the knack to do this gently. If the touch digitizer glass wasn’t cracked before, I’m sure it would have cracked after I tried to pry it free. Thankfully it was already cracked, so this was merely even more cracked. And I’m thankful for the clear packing tape I applied earlier, they were able to hold most of the pieces together. If you are planning to tackle this task and wanted to see how much glue you’ll need to fight, this pictures should help.

What was my reward for all this work? The intact display screen module underneath the (now extremely cracked) touch digitizer glass. I had feared it was held by its own adhesives, but the Amazon engineers apparently decided the adhesive on touch digitizer is enough to keep both of these components in place. The screen was held by only a few thin strips of tape, and here I am thankful I removed the battery earlier as it allowed me to push from the back and pop it free.

There was a side bonus here: the tablet chassis held two small magnets. Probably for a tablet screen cover accessory, but now I want to free them. The good news is that I don’t care about preserving the tablet chassis, the bad news is that magnets are brittle and can break under stress. I misjudged how thick they were and broke one. But now I knew they were thin and only held by a strip of double-sided tape, I was able to use a thin blade and cut the other free while keeping it intact.

Once the magnets were recovered, there was nothing else I wanted from this tablet chassis frame and it will head towards landfill while I examine my prize: the LCD module.

Amazon Fire SR043KL Battery and Digitizer Cable

After I moved the mainboard more-or-less out of the way, my next objective was to remove the glued-in battery. This is not just annoying, it is potentially dangerous as lithium polymer pouch batteries like these aren’t very fond of gross physical abuse. And they have a history of protesting their displeasure with a fireworks show in your face! There were two ways forward: I could leave it alone and hope it doesn’t block anything important, or I can remove it now to uncover whatever is underneath and remove a point of volatility from the project. I decided to remove it.

The battery is pretty much surrounded on all sides, but I saw Amazon engineers left a small opening as an entry point. Here it is marked after the fact.

I didn’t see an applicable tool in my iFixit repair toolkit, so I cut apart a piece of thermoformed plastic packaging for a thin and flexible spatula to dig in. I found the bottom strip of tape, and after that I was freed, I could work my way around to free the battery from the remaining three strips. That is a total of four strips of double-sided tape, one for each edge of the battery.

Thankfully the battery did not explode in my face, but I’m not entirely sure it came out unscathed, either. There were some very definitely flexing as I pulled it freed from these four tape strips, because at the time I didn’t know exactly where they all were. Perhaps with a bit of hindsight I could free the battery while putting less stress on it, but I could at least document my findings so maybe the next person who sees this can treat their battery better.

During all of this yanking and pulling of battery removal, I flexed the touch digitizer cable one too many times and it broke. Oops. Well, at least now the mainboard has been completely freed from the case.

Earlier I thought this Kapton-covered segment might have been soldered to the board and didn’t want to pull too hard. Now that I’m no longer worried about damaging this already-damaged part, I stabbed a flat tool in there to release the bond. It turns out there was no soldering, just a piece of tenacious double-sided tape.

There were a few other trivial items accessible from the back of the tablet, including the external speaker, microphones, and switches for external buttons. I was moderately curious about these items, but I had actually hoped to find something that would help me release components on the front side of the tablet. Alas, I found nothing, which meant there’s only one thing to do: start fighting glue.

Amazon Fire SR043KL Mainboard

I’m tearing apart an Amazon Fire tablet (SR043KL) with cracked front glass, and knowing full well this low-budget device would not have been designed to be easily serviceable. After I popped off the back shell, I quickly ran into things held by adhesives of one type or another. My first focus is to see if I can free the mainboard.

The easiest item to release is the battery connector. Two screws held a reinforcement metal plate and, once those two screws were removed, the battery connector popped free easily. On the right side of the battery, I had to peel off some tape to reveal a fairly standard connector for these ubiquitous Kapton yellow flexible circuit boards. The rear facing camera connector easily popped free, but peeling it away from double-sided tape holding it in place took more effort. On the upper-right corner was an enigma. I would eventually learn this was the cable for the touch digitizer glass panel, but after I freed the small connector nothing came loose. The large yellow square was held tight and I didn’t want to pry too hard in case it was soldered underneath to something. I left this for later.

After I removed every visible screw, the mainboard remained stubbornly in place. Poking and prodding all around, I eventually noticed these two plastic claws.

Once freed from these claws, I could flip the mainboard over, still connected by the black touch digitizer cable I had yet to remove.

From here we can see metal reinforcement for the USB port and audio jack, each held down by two screws on either side of the corresponding socket. I think the red rubbery part is a cap over the microphone, next to the front-facing camera module. Springy metal fingers make contact with parts on the chassis. From left to right they are: power button (only two out of three contacts are used), the volume up/down buttons (only three out of four contacts used) and the WiFi/Bluetooth antenna. (All three contacts used.)

I had hoped there would be something interesting to see on this side of the board, but no luck. The opposite side is mostly hidden under soldered-on metal shielding, I think I need a heat plate to remove them nicely. For the moment, components on the mainboard would have to remain a mystery. So I set it aside and started working on a stubborn battery, accidentally severing the touch digitizer cable while doing so.

Amazon Fire SR043KL Teardown Begins

Encouraged by my success salvaging an useful backlight from a cracked laptop screen, I pulled out another cracked screen from my pile of retired electronics destined for teardown. Today’s subject: an Amazon Fire tablet, model SR043KL which appears to translate to the now-obsolete 7-th generation(*) of the product line.

The primary goal of these devices are to put an Amazon shopping portal into our hands, and thus the hardware cost has been subsidized in the expectation of future sales. This was made quite explicit with the bargain “With Special Offers” edition that display more ads than the standard edition. As a side effect, there is little economic incentive to repair these devices. For example, a replacement touch digitizer glass panel(*) for this tablet costs roughly $25, which is half of the normal price for a new Fire tablet(*). Which, by the way, nobody should pay $50 for because Amazon frequently puts them on sale for less.

I got this tablet from a friend who saw no reason to try to fix something when just the parts cost is at least half the cost of a replacement. And he’s not alone. The demand for repair information is so minimal that not even our trusted resource iFixit offers much help. No teardown, no repair guide, and only a few questions on the forums. For a “better than nothing” resource I poked around to find a teardown guide for a different Fire tablet to get a rough idea of what to expect.

With memories of shattered glass fresh in my mind, my first priority was to put some clear packing tape over the screen. Reducing the likelihood of flying shards of glass if it should break apart under stresses of my prying. Given the lack of serviceability typical of devices built to low price targets, I expect a lot of prying on glued-in parts.

Using trusty tools from iFixit I started digging into the seam between the bright yellow plastic and the front face black plastic.

I would not have been surprised if the colorful backshell was glued in, but thankfully it was not. Merely held by plastic clips all around the perimeter that I could pop free.

The internal volume is dominated by the battery, which is pretty typical of tablets. The battery connector is reliably held in place by two screws that I could release to unplug the battery, but the battery itself is glued in place. Over on the right just above the battery is the screen display cable, but it is held down by tenacious tape. The rear-facing camera looked like it might easily pop out, but it is also held down by tape. The black ribbon cable in the upper right is for the touch digitizer, and it is held down by tenacious double-sided tape. And I see a speaker in the lower left, which is held by… you’ll never guess…

In summary, once we pop off the back cover, there’s little else that can be done without doing something irreversible. Almost everything else would require tearing some adhesives loose. I decided to start with the system mainboard.

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

Investigating TI TPS61187 WLED Driver

I took apart a LG LCD panel LP133WF2(SP)(A1) hoping to salvage something useful. After I failed to salvage the polarizer film, my hope lies with the backlight module. Its diffuser had a multi-layer construction I didn’t understand but found fascinating and wanted to see it light up firsthand. And if I am to do that, I need to figure out how to send power to the backlight LEDs. When I split the panel into the display and backlight modules, I saw the backlight was connected by a ribbon cable with seven conductors. Six of them look identical, and the seventh was wider than the rest, making it a good candidate for either a common anode or a cathode. Which is it, though? For that I looked for hints on the display panel’s integrated driver board.

There were three significant-looking ICs on board. The largest is closest to the connector to the rest of the laptop and the top two lines written on it were “LG Display ANX2804”. I found no information on this chip online. In the middle of the circuit board is another IC, this one labeled “SM4037 DA1422 AMER038”. I found no information on this particular designation, either. (There exists a SM4037 from Fairview Microwave, but it is a connector and not a microchip.) That leaves the chip closest to the backlight connector as the best candidate for a LED driver, and luckily its markings of TPS 61187 match that of a Texas Instruments WLED driver. I think this is it.

Reading its publicly available datasheet reinforced it is the right result, as its “typical application” diagram shows the chip driving six parallel strings of LEDs. The schematic indicates the six strings are connected to a common anode with their own individual cathodes wired to one of six current sinks on the chip. This information is enough for me to wire up this array to my bench power supply to find the right voltage for this string and create my own LED driver circuit. But since I have the datasheet already on hand and a “I know it used to work” backlight control board, I kept reading to see if I could perhaps reuse the board as well.

It looks pretty promising. There are no handshake or control protocol involved, all the potential configurations for this chip are done via resistance values to certain pins which would be already present in this case. I think for a bare minimum setup I only need to provide a power source and a PWM signal to control brightness. I could also connect the enable pin but I think I could get away with using a pull-up resistor. And under this minimalist plan I would be ignoring the fault signals. Plus one very important lesson about its power supply I had to learn first.

LG LCD Panel Backlight Also Has Layers

I’ve got a cracked laptop LCD module by LG, model LP133WF2(SP)(A1) and I am taking it apart to see what’s inside and maybe salvage fun stuff for future projects. After I failed to learned lessons about salvage the polarizer film, my adventure continues with the backlight module. My ambition is to make it light up again as a diffused light source, hoping it’ll be more pleasant than the point light sources of individual LEDs.

I foresee a decision that I will have to make: do I work with the LEDs directly with its seven-conductor cable? Or do I try to work with the LED driver IC on the board?

But before I get that far, I wanted to examine the physical construction of this laptop LCD backlight. There wasn’t much to it at first glance, just a big flat expanse of white matte material.

I had expected a thin row of LEDs and some sort of light diffuser material, and I saw… just diffuser. The LEDs must be incredibly thin to hide under this black strip which is only about 2mm wide.

I had expected the diffuser material to be a translucent sheet of plastic. When I lifted it away from the frame, I found it’s actually composed of four layers. The top and bottom layers are close to what I had expected, they are translucent but are visibly different from each other. The surprise came in the middle two layers, which had optical properties that reminded me of a Fresnel lens but not in a concentric pattern as usually found in Fresnel lenses.

I’m ignorant on how to characterize this any more specifically, but it feels like an entire discipline of engineering that I have never known before. There are experts out there for this intersection between physics (optics) and manufacturing to mass produce these backlight elements. At some point I hope to learn the technical terms of this material so I can learn more about them. But right now this discovery makes me even more motivated to get the backlight back up and running so I can see this stuff in action. Which means it’s time to read up on that LED driver IC.

Turning to Chemistry for LCD Panel Polarizer

I thought it might be fun to salvage the polarizer from a broken laptop LCD screen, but it has put up quite a fight. I first tried direct mechanical brute force and managed to shatter the glass. Thankfully, not injuring myself doing it. When physical power doesn’t cut it, we turn to chemistry.

The risk of this approach comes from the fact the polarizer is made of plastic of unknown composition. Ideally I could find a solvent that will dissolve the adhesive and leave the plastic intact. If I was better at chemistry I might have some methodical way to find that solvent, but all I’ve got is trial-and-error. To aid in the trial-ing (and the error-ing) I have a portion of the polarizer I’ve already freed from brute force, carrying with it a layer of tacky glue. It’s enough for me to get started.

I had a rough progression of least- to most-aggressive solvents. First up to bat was 70% isopropyl alcohol, and the glue just laughed at its feeble efforts. After I let the alcohol dry, I tried WD-40, which also did nothing. I wiped up as much of it as I could before moving on to the next contestant: Goo-Gone.

Goo-Gone had some effect. It did not magically dissolve the glue as it tends to do with most other glues I come across, but it did soften this stuff somewhat, and it didn’t seem to damage the plastic. Using Goo-Gone to soften the glue, I was able to peel the sheet of polarizer free of the remaining glass and finally freed myself of the risk of puncturing some body part from thin pieces of broken glass.

However, that’s only half a victory as the glue remained stubbornly attached to the plastic making it unusable for light polarization fun. More Goo-Gone only seemed to spread it around and didn’t dissolve it. So I moved on to the next item: mineral spirits. It further softened the glue enough for me to start rubbing them off the plastic. It was a very labor intensive process, but I could start to see the shiny surface of my polarizer sheet. But I soon reached the limits of this approach as well. I started sensing uneven bumps in the surface and I couldn’t figure out what’s going on until I dried off all the mineral spirits for a look.

It appears there are multiple parts to this glue, and there is a much tougher component that clung on to the film. They were applied in lines and that explained the ridges I could feel in my fingertips while this film was damp with mineral spirit.

Finding the limits of mineral spirits for this task, I moved on to acetone a.k.a. nail polish remover. This is something I knew could melt certain plastics, as it’s used to smooth and weld plastic parts 3D-printed in ABS. However, I also knew it is not equally destructive to all plastic, as it seems to do very little (or absolutely nothing) to 3D-printed PLA parts and acetone itself sometimes comes in plastic bottles. Lacking experience in identifying plastics, I proceeded on my trial-and-error process.

The good news: using a small amount of acetone in a test corner, I found that it quickly dissolved the adhesive, turning them into soft goop that are trivial to remove. Wiping it off, I see the clear surface of polarization film with no evidence of chemical etching or erosion. I think this is the ticket!

But then I went too far by soaking the entire sheet in acetone, expecting to pull out a completely clean polarizer. When immersed in acetone, the polarizer film became brittle and cracked into little pieces. It marked the end of this experiment, but next time (I’m confident there’ll be a next time) I’ll try a few intermediate steps to see if I can find a good point on the spectrum between “few drops in a corner” and “soaking the entire sheet.”

Trying to salvage something from this screen’s LCD module was a bust, but I still have a very fascinating backlight module to play with.

Layers of Glass in LG Laptop LCD

I have a broken laptop LCD display module that I’m taking apart. It is a LG LP133WF2(SP)(A1) and it came from a Toshiba Chromebook 2 which was retired due to said cracked screen. I was able to split it into its two main components, the backlight and the display, both connected to the integrated driver circuit board. The backlight connector was something I could disconnect and reconnect, which is not something I could say for the high density connectors to the front display panel. Fortunately the screen is already cracked and nonfunctional so the majority of risk of disassembly is from broken glass.

The edge of this display module made it clear there is a complex multi-layer sandwich within.

There are at least three layers. The topmost layer is very thin and feels like plastic. The middle and bottom layers feel like glass. They don’t come apart easily, so I thought I’d try peeling the top plastic layer like a sticker. It is indeed backed by some adhesive, pretty tenacious ones at that.

I tried to keep the glass layers as flat as I could while I peeled, a difficult task with the strength of that glue which resulted in some alarming flex in the glass. I double and triple checked to make sure my eye protection is in place while peeling. After several centimeters of progress, scary bending and all, I felt a “pop” as the flexing freed whatever had held the middle and bottom glass layers together around their edges. Once this corner popped free, it was trivial to travel around all edges to peel the two glass layers apart.

It was damp between these two layers, presumably a thin layer of the “liquid” in Liquid Crystal Display (LCD). It was easily absorbed by a single sheet of paper towel, and its oily residue cleaned up nicely with 70% isopropyl alcohol. As far as I know, this is not a toxic material and I had not just cut years off my life, but I went and washed my hands before proceeding.

The bottom layer is where the original crack had lived, and these cracks had gotten worse due to the recent flexing. I don’t see anything of interest in this layer so I set it aside for safe disposal.

The two glass layers each had a grating that can be barely felt with my fingertips. They are also visible if I shined light through each layer. They are orthogonal to each other which would make sense if one set controlled horizontal pixels and the other controlled vertical pixels. Also, once the two glass layers separated, I was able to confirm the passive polarization filter (one of the objectives for salvaging) is the flexible sheet of plastic I had been tugging on. I resumed peeling that layer but didn’t get much further. Now that I only have one glass layer instead of two, it shattered under stress.

Even though I expected this as a potential (likely, even) outcome, it was still a surprise when things finally let go. Three cheers for eye protection! I picked out a few tiny shards of glass from my fingertips, but none of them found a blood vessel so there was no bleeding. And I think I managed to collect all the pieces scattered around the table. I had thought this would be a minor setback and I could continue peeling but just with smaller pieces of glass, but I was wrong. I don’t know my glass properties very well, but something happened here to change the mechanical properties of the glass. Once the first break happened, it has almost no strength at all. Continuing to peel — even at a lower force — causes new breaks. Brute strength will take me no further. And when brute strength fails, I turn to chemistry.

LCD Panel Driver Circuit Board

I’m taking apart a broken laptop LCD panel, a LG LP133WF2(SP)(A1) from a Toshiba Chromebook 2. I started with the very fancy tape surrounding the edges. Once the tape was gone, its top edge started unfolding into two parts. But they’re still held together on the bottom edge with the integrated driver board for this display. So I should figure out what that’s about before trying to completely separate the two parts.

The front side of this board had three sets of extremely high density connectors to carry signal for all 1920×1080 pixels on this module.

The back side of this board had all of the integrated circuits and a lower density connector for the backlight.

A single cable carried both power and data from the laptop mainboard. The chip closest to that connector was the largest IC on this board and probably mastermind in charge of this operation.

A search for “LG ANX2804” came up empty, which is not a huge surprise for a chip designed and built by LG for internal consumption by their display division. There’s no reason for them to distribute specifications or datasheets. On the other side of the board we see a connector for the backlight. The connector has nine pins, but in the ribbon we see six thin wires plus a wider seventh wire. This wider wire consumes two of the nine pins, making it a good candidate for either a common anode or cathode for LEDs. This left one pin in the connector seemingly unused.

I had expected just two wires for a simple string of LEDs, but the backlight is evidently more complicated than that. I’m optimistic I can get this figured out because the IC closest to this connector is clearly marked as a TPS 61187 by Texas Instruments, and I hope the information available online will help me sort it out later.

Returning to the front of this board, these high density data connectors are fascinating but I don’t understand everything that’s going on here.

I count somewhere between four and five contacts within a millimeter. This is definitely beyond my soldering skill, but they aren’t soldered anyway. Whatever this type of connection is, it is clearly single use. Once I detach it (it peeled off like tape) there’s no way for me to reattach it. I see nothing to help me align the connector. I’m also curious about the fact the copper contacts area is wider than what we see actually used. I’m sure it’s a provision for something but I don’t know what. For today it doesn’t matter, as the screen is already cracked and nonfunctional so I lose nothing by peeling them off before I explore its intricate layers of glass.

LG LCD Panel LP133WF2(SP)(A1) Teardown

After I checked the USB OTG reader off my teardown to-do list, I decided to continue ignoring what I had originally planned to do and continued tearing down another item that’s been sitting on my teardown to-do list: a broken LG LCD panel LP133WF2(SP)(A1). It was the original screen in a Toshiba Chromebook 2 (CB35-B3340) which I received in a broken state with the screen cracked. I revived the Chromebook with a secondhand replacement screen, and I set the original cracked screen with the intent of eventually taking it apart to see what I can see. “Eventually” is now.

Out of all the retired screens in my hardware pile, this was the most inviting for a teardown due to its construction. The ever-going quest for lighter and thinner electronics meant this screen wasn’t as stout as screens I’ve removed from older laptops. I noticed how flexible it was and it made me nervous while handling it. Most of the old panels I’ve handled felt roughly as rigid as a thick plastic credit card, this display felt more like a cardboard business card. I’m sure the lack of structure contributed to why the screen was cracked.

The primary objective of this exercise is curiosity. I just wanted to see how far I could disassemble it. The secondary objective is to see if I can salvage anything interesting. While the display itself is cracked and could no longer display data, the backlight was still lit and it would be great if I could salvage an illumination panel. And due to how LCDs work, I know there are polarization filters somewhere in its sandwich of layers. I just didn’t know if it’s practical to separate it from the rest of the display.

The primary concern in this exercise is safety. The aforementioned quest for light weight meant every layer in this sandwich will be as thin as it can possibly be, including the sheets of glass. And since the screen is visibly cracked, we already know this activity will involve shards of broken glass. I will be wearing eye protection at all times. I had also thought I would wear gloves to protect my fingertips, but I don’t have the right types for this work. All the gloves I have are either too bulky (can’t work with fine electronics in gardening gloves) or too thin to offer protection (glass shards easily slice through nitrile.) I resigned to keeping a box of band-aid nearby.

All that said, time to get to work: around the metal frame this panel is surrounded by a thin black material that contributes nothing to structure. It’s basically tape. Cut to precise dimensions and applied with the accuracy of automated assembly robots, but it’s adhesive-backed plastic sheets so: tape.

The adhesive is quite tenacious and it did not release cleanly. Once peeled, the top edge of the LCD array could separate from the backlight. The diagonal crack is vaguely visible through the silvered mirror back of the LCD.

This is a good start, but I can’t pull them apart yet. Right now they’re both connected to this panel’s integrated driver circuit board.

Rosewill USB OTG Memory Card Reader (RHBM-100-U2) Teardown

I got this thing from a “Does Not Work” box intending to do a teardown. Since it’s so small, I thought it would be fun and quick, but I kept putting it off. It’s been sitting adjacent to my workbench through several reorganizations and cleanups, and I kept moving it from one place to another. Today I was about to move it again when I decided: No more. I have other things I need to do, but I’m putting them on pause for this thing. Today is the day.

Based on all the slots on one side, this is clearly a multi-format flash media reader/writer. The other end was a little more interesting, as it is a USB micro-B plug instead of the usual socket. The presence of the plug implies this was designed for use with USB OTG devices such as an Android phone, allowing them to read and write flash cards. Aside from a few labels for the various types of flash media, there was only the “Rosewill” brand logo. I found no model number or serial number printed on the enclosure. Searching for “Rosewill USB OTG” retrieved information on many products. The closest match based on pictures is the RHBM-100-U2.

There was a visible seam around the faceplate full of memory slots. The remainder of the enclosure appeared seamless. The lack of fasteners indicate this faceplate is glued in place. Using pliers, I was able to get a bite out of the enclosure to use as starting point. Not elegant, but I’m going for speed in this teardown and elegance be damned.

The bite allowed my pliers to get a firm grip on the faceplate and peel all around the perimeter. After that, I could pull the faceplate free.

Once the faceplate was removed, a firm push on the USB micro-B plug popped the final few glue points free and I could slide out the PCB. As expected, it was relatively simple dominated by surface mount flash media connectors.

Aside from those media connectors, one side was dominated by small passives.

The other side had one IC clearly more sophisticated than anything else on the device. The only other unexpected item is the black goo on the USB micro-B plug. I have no idea why that is there.

Searching on “GLB23” didn’t get me anywhere, but “GL823” got a likely hit with Genesys Logic. It is advertised as a single-chip solution for implement a multi-format USB media card reader, which is a perfect match for the device at hand. I didn’t bother downloading its datasheet, but I wouldn’t be surprised if this device basically followed the reference design.

Years after I picked this up, intending for a quick teardown, I finally did it. It no longer needs to occupy space on my workbench and I can move on with my life.

Western Digital My Book 1TB (WDBACW0010HBK-01) Teardown

I took apart an external USB 2.0 hard drive I had formerly used for MacOS Time Machine, but haven’t touched in years. It was the second of three external drives under two terabytes that I had gathering dust. The third and final drive to be disassembled in this work session was used for a similar purpose: the Windows Backup tool that (as far as I can recall) was introduced in Windows 8. Now it will serve that role again, sort of, by becoming part of my fault-tolerant ZFS RAIDZ2 storage array running under TrueNAS. Which does not support USB external drives, so I am removing the bare drive within for its SATA connection.

Like the other two drives, this one lacked external fasteners and had to be taken apart by prying at its seams to release plastic clips. (Not all of the clips survived the process.)

The geometry was confusing to me at first, but following the seams (and releasing clips) made it clear this enclosure was made of two C-shaped pieces that are orthogonal to each other. I thought it was a creative way to approach the problem.

I was also happy to see that the cooling vents on this drive was more likely to be useful than the other two, since the drive is actually exposed to the airflow and it is designed to stand on its edge so warm air can naturally escape by convection. There is no cooling fan, and none was expected.

Like the other two drives, there’s a surface mounted indicator LED on the circuit board. To carry its light to the front façade, there’s an intricately curved light pipe. It might look like a flexible piece of clear plastic in the picture but it is actually rigid. I was a little sad to see that, because its precision fixed curvature means there’s almost no chance I can find a way to reuse it.

Two circuit boards are visible here. The duller green board is the actual hard drive controller circuit, the brighter green board is the USB3 adapter board converting it to an external drive. My goal is to remove the bright green board to expose the bare drive’s SATA interface so I could install it in my TrueNAS server. It was quite stoutly attached! On the other two drives, once the internals were exposed I could easily pull the drive loose from the adapter board. This board was rigidly fastened to the drive with two screws, including this one that took me an embarrassingly long time to find. On the upside, this rigidly fastened metal reinforcement meant the USB3 port is the strongest I’ve seen by far. Another neat feature visible here is a power button, a feature I don’t often see on external drives.

This assembly was mounted inside the external case with some very custom shaped pieces of rubber for vibration isolation. Like the light pipe, I doubt I would be able to find a use for these pieces elsewhere. But that’s fine, the main objective was to retrieve the SATA HDD within this enclosure and that was successful.

This is enough hard drive “shucking” for one work session. I have more retired drives (two terabytes and larger) awaiting disassembly, but I think I have enough to satisfy my TrueNAS array replacement needs for the near future.

Seagate Expansion External Drive 1.5 TB (9SF2A6-500) Teardown

The terabyte drive shucking series continues! Second in this work session is an older Seagate external drive with a slower USB 2.0 interface. They dropped out of favor after USB 3.0 came on the scene, but that’s only a limitation imposed by the external enclosure. I’m confident the hard drive within will be just as fast as the others once I’ve pulled it out and can connect it via SATA to my TrueNAS ZFS storage array. This particular drive served as my MacOS Time Machine backup drive and exhibited some strange problems that resulted in my MacBook showing the spinning beach ball of death patience while the drive makes audible mechanical clicking noises trying to recover. I no longer trust the drive as a reliable single-point backup, but I’m fine with trying it in a fault tolerant RAIDZ2 array.

Again I had no luck finding fasteners on the external enclosure, so I proceeded to pry on the visible seam. I was rewarded by the sound of snapping plastic clips and lid released.

Despite the visible ventilation holes, it seems like the hard drive is actually fully enclosed in a metal shell. I guess those vents didn’t do very much. The activity light in this particular drive was not as clever as the previous drive, it is a straightforward LED at the end of a wire harness.

Unlike the previous drive, which had an external shock-absorbing shell, this drive’s vibration-isolating mechanism is inside in the form of these black squares of soft rubber.

The screws have standard #6-32 thread but have an extra shoulder to fit into these rubber squares. I feel these would be easily reusable so I’m going to save them for when I need a bit of shock absorption.

Once those four screws were removed, the bare drive slid out of the case easily. I didn’t need to bend the top of the sheet metal box to remove the drive, I did it so we can see the circuit board in this picture.

When I added this bare drive to my ZFS array, I had half expected the process to fail. If the clicking-noise problem persists, I expect TrueNAS to fail the drive and tell me to install another. I was pleasantly surprised to see the entire process completely smoothly. There were no audible clicking, and TrueNAS accepted it as a productive member of the drive array. I wonder if the problem I encountered with this drive was MacOS specific? It doesn’t matter anymore, now it helps back up data for all of my computers and not just the MacBook Air. It’ll share this new job with one of its counterparts, who formerly kept my Windows backups.

Seagate Backup Plus Slim Portable Drive 1TB (SRD00F1) Teardown

I remember when consumer level hard drives reached one terabyte of capacity. At the time it seemed like an enormous amount of space and I had no idea how I could possibly use it all, and where the storage industry could go when additional capacity didn’t seem as useful as it once did. The answer to the latter turned out to be solid state drives that sacrificed capacity but had far superior performance. SSD capacities have since grown, as our digital lives have also grown such that a terabyte of data no longer feels gargantuan.

As someone who has played with computers for a while, I naturally had a pile of retired hard drives. An earlier purge dismissed everything under one terabyte, but with the wonder of the terabyte milestone still in my mind I held on to those one terabyte and higher. This became sillier and sillier every year, especially now that the two worlds have met back up: Sometime within the past year I noticed I can buy an one terabyte solid state drive for under $100 USD.

In this environment, the only conceivable use I have for these old drives is to put them together into a large storage array, which motivated me to retire my two-drive FreeNAS box. My replacement running that operating system (which has since been rebranded TrueNAS) put six of my old terabyte drives to use as a RAIDZ2 array, resulting in four terabytes of capacity and tolerance of up to two drive failures. In the year since I’ve fired these old drives back up, I was a bit disappointed but not terribly surprised some of these old drives have already started failing. It’s not a huge worry as I had plenty more drives waiting in reserve. However, some of them are sitting inside external enclosures and need to be shucked in order to retrieve the disk drive within. First up: the Seagate Backup Plus Slim Portable Drive (SRD00F1) This will be a smaller 2.5″ laptop-sized drive with slower performance, but that should be fine as a member of a large secondary storage array.

I used this drive for a while as portable bulk storage to hold stuff that didn’t fit on my laptop’s small SSD, so it had to be something durable enough to be tossed in my backpack without too much worry. I was enamored with the design, which had an impact absorbing exterior of blue rubber that also incorporated a flexible band to hold the corresponding cable cable while in my backpack. It had an USB 3 micro B connector which I rarely see beyond external hard drives like these.

As a small portable drive, there were the expected lack of visible fasteners. Perhaps something is hidden under the sticker?

Nope, no fastener there. Without stickers, this device must be held together by either glue or clips. Most of the body is black plastic and the top feels like a sheet of metal, so the gap between them is the obvious place to start prying. It didn’t take a lot of force to break the top free from some indents cast into the plastic, but it’s enough force to bend the metal. I had passed the point of no return: this drive will never come back together nicely.

The top was held by both double-sided tape and a plastic ring that helped it clip onto the body. I thought it was very clever how they designed the activity indicator light. Under the metal slit is a block of white tape (still attached to the lid in the picture below) serving as diffuser for the LED. The LED is on a circuit board that is almost completely enclosed by foil tape, but there’s a small hole cut in the tape for the LED to shine through.

There were no fasteners inside the case, either. Once the lid was removed, the drive came out easily.

Here’s a closer look at the drive, with its electronics still inside the foil tape. The rectangular hole for activity LED is visible on the right, with the LED itself peeking through.

After the adhesive-backed foil was removed, I could pull off the adapter circuit board. It is an admirably minimal design to bridge USB3 to SATA. The orientation of the board was a surprise, I hadn’t know there were vertically-standing surface-mount connectors for USB3 micro-B and for SATA connectors. Most of the connectors I’ve seen sit flat on the same plane as the circuit board, not orthogonal to the board like these.

At the moment I don’t foresee anything useful I could do with this board, but at least it is tiny so I can toss it into the hoard as I await ideas. In the meantime, it’s onwards to the next retired hard drive.

Spektrum SR300 Receiver Teardown

I have a Spektrum DX3E transmitter designed for radio control ground vehicles, with a matching Spektrum SR300 receiver for mounting on the vehicle. I want radio control equipment like this to be one of many options for controlling a Micro Sawppy rover, and my DX3E will be my example RC equipment for developing corresponding ESP32 software. Before I dive into the software, though, there is a minor hardware modification I wanted to make.

There are several conventions for radio control servo plugs, which look superficially similar to generic 0.1″ pitch wire connectors but aren’t quite identical. From my past experience I knew of the “Futaba” style, with a tab to help with proper alignment. I didn’t have many of those on my radio control toys. Most of my old equipment conformed to the “JR” style, which lack the tab but have tiny bevels to prevent plugging a servo into the receiver backwards. Commodity micro servo plugs do not have this bevel, and neither will Micro Sawppy ESP32 plug. While it is theoretically possible to manually cut the necessary bevel in a generic 0.1″ pitch three-position connector, I have several connectors in mind for experimentation and that would quickly get tedious. So for my own experimentation purposes, I decided to cut off the wedges that enforce bevel direction on the receiver instead. This is not necessarily something I recommend for others. If they only have a single device, it’ll probably be better to cut bevels.

I didn’t want to cut off those wedges with with the receiver intact, because a slip of the blade might damage its circuit board. So I’ll take it apart, which gives me a chance to look inside as well, something I always enjoy. There were no elaborate security measures, merely four small Philips head screws. Once they were removed, the case comes apart easily. In my case, a few grams of dirt fell out as well. Results of my RC cars going off track due to pilot error.

Here is the top side of the receiver. Marked with the year 2008, it reminded me how long it’s been since I played in this hobby. Looking over the components, I was not surprised by capacitors to buffer power input and the oscillator to maintain accurate frequency. There is a large IC clearly in charge of the operation, but it is unmarked. We do see an array of five pins marked J1 that looks like a debug header, but I’m not terribly interested in poking into this chip right now. The output signals pins were a surprise. I had expected some sort of a transistor array to let the main IC toggle signals on and off at the same output voltage as the input voltage. However, all I see are little resistors (R2 – R5) implying they are merely there to limit current draw on IC output pins. This is worth following up.

The back side of the circuit board confirms power and ground pins are connected in parallel across all output pins, with the four signal pins separate as expected. I see a lot of surface imperfection here. It looks like corrosion which might be reaction to the dirt that has been trapped in here. It may also be something from the factory, possibly excess soldering flux that was not cleaned up. I also see a sticker marked ST104M but I have no idea what that represents. Maybe a firmware revision number?

The circuit board was interesting, but for today they were merely a side show. I just wanted it out of the way as I cut into the enclosure. With the PCB removed I could confidently wield my blade, and the little wedges were quickly removed.

The receiver reassembled easily, and a quick test confirmed I could now plug in and use generic micro servos (or other devices) without interference from those now-gone little wedges.

TT Gear Motor Teardown

Commodity TT gearmotors became the center of my attention once I decided to switch to using DC motors for driving wheels on my little Sawppy rover project. Where did this form factor come from? Why do people call them TT? Why are most of them yellow? I don’t have answers to those historical questions, but I will see if I can build a little rover with them.

The adventure starts with buying a batch and taking one apart to see what’s inside. I’m not sure if the commodity TT gear motor market has diversified implementation like the micro servo market. If this experiment with TT motors go well, I expect I’ll buy more batches in the future for more little rovers and I’ll open those up to look for differences. Right now I could only speak to this one.

Externally, we see three mounting points. Two mounting holes go through the entire gearbox, next to the two screws holding the gearbox together. A third mounting hole is on a thin tab at the end opposite from the motor. There are two attachment points to the output shaft, which appears to be symmetric and have identical detent patterns. Turning the output shaft by hand, I can see the other output shaft moves in sync, but that doesn’t necessarily mean it is a single piece.

While the output shafts appear symmetric, the rest of the gearbox almost but not quite symmetric. The motor is offset by a little over a millimeter away from the camera in these pictures. On the side facing the camera, we see a little nub above the axle, whereas its opposite side is smooth.

The motor is held in place by a band of clear elastic plastic held by hooks molded into the gearbox exterior. In this particular unit, the clear plastic has partially melted into the yellow plastic and had to be peeled off with pliers before I could stretch them for removal. Once the clear plastic is removed, the motor can slide out. (To release just the motor, it is not necessary to remove the two screws seen in this picture.)

The motor looks very much like a commodity form factor used in many battery-powered toys. In disassembly and hacking circles I frequently see it referred to as “Mabuchi motor”. But just like “JST connector” this is not precise enough. Mabuchi Motor Company has a large product line, most of which aren’t this thing. I found references to this sized motor as FA-130, but with such commoditization I’m certain the majority aren’t genuine Mabuchi products. There’s certainly no Mabuchi logo on this particular motor.

What’s important for the purposes of project creation is that this is a common form factor. And thanks to its use in products like the Tamiya Mini 4WD product line, we can get motors with a wide range of performance characteristics. Same external motor dimensions, but different tradeoffs for torque vs. max speed, etc. At least that’s the theory, I won’t know for sure until I try buying one of those Mini 4WD Hop-Up motors and try installing it in one of these gearboxes.

With the two screws removed, I could open up the gear box and see the gears inside. Pulling the gear train apart, I find four separate components.

My first observation is that all the gears appear to have different diameters. I’ve seen a few TT gearbox modding guides that claim I could select different gear ratios by flipping some gears around, but I don’t see how that is possible when the gears are all different diameters. I’m either overlooking something, or this unit is the wrong variant for that mod to work.

My second observation is that the output shafts poking out on both sides of the gearbox are indeed part of a single piece shaft. There are no ball bearings here but at least they are supported on both sides of the shaft. However, since the output shaft is very clearly asymmetric, I should pay attention to which side is used as the main weight bearing member. Looking at this teardown, I have a clear preference for the side further from the camera in these pictures. That side of the shaft has far more support, in the form of a plastic tube approximately 8mm long. The side closer to the camera (and laid flat against the surface in these pictures) has only a thin wall of plastic for support.

I wonder if there’s a situation where the opposite is true? Perhaps when torque is a concern and we want to be closer to the final output gear, in order to minimize torque imposed on the shaft? I don’t think that’s likely at this power level, but I’ll keep an eye open for the possibility.

I didn’t need to take apart this DC gearmotor to use it, but having seen its insides I feel more confident approaching the task of mechanically adapting it to rover duty. In the meantime, I have a parallel adventure of learning how to drive these motors electrically.

Monoprice PowerCache 220 Teardown

After a service life of over two and a half years, this Monoprice PowerCache 220 was retired due to its degraded battery and malfunctioning thermal protection system. I bought a Paxcess Rockman 200 to replace this old workhorse, which is now long out of warranty and has also been discontinued. Can I fix it? Should I fix it? I won’t know until I take it apart and see what I can find out.

The first step is removing side panels. They are held by hex-drive socket head fasteners that appear to be large durable machine bolts.

Once freed by a hex wrench, however, we see it was an illusion. Underneath the big beefy top is a short self-tapping screw fastened to the plastic. I don’t recall ever seeing a self-tapping fastener with a hex-drive socket head before today.

Once the tough-looking (but actually not) fasteners have been removed, the side panels could slide downwards roughly 1cm, then they can be freed.

With the sides removed, we’ll need to remove the rear fasteners. This is fairly straightforward, none are hiding behind labels. They are all self-tapping Philips screws in clearly visible recessed round holes.

Once those screws are removed, rear half of the enclosure can be lifted to expose the remaining attachment point: a wire harness for the cooling fan mounted in the rear enclosure.

It was easy to unplug the fan (looked like a JST-XH polarized connector) to get a clear look at the interior. Most of the available volume is allocated to a large sealed lead-acid battery. The battery is surrounded by a few pieces of foam padding, probably so it wouldn’t rattle around as the unit is carried around..

This PCB is dominated by large components we would expect to see in a power control application.

Attached to the aluminum heat sinks are power control MOSFETs.

The Golden Rule of Teardowns: Whenever an identifier is visible, put it into a web search to see what comes up. Unfortunately we’ve got nothing for SGD005-INV. In time, the search engines will find this page and send people here. I apologize in advance to those who come to this page seeking information I don’t have.

I was pleasantly surprised to see an easily replaceable fuse. It looks like a standard blade-style fuse popular in automotive applications. I feel it is on the lenient side as 35A * 12V = 420 Watts. I agree if this fuse blows, something has gone very very wrong, but I’m not convinced it’ll blow early enough to protect the rest of the device.

I had expected unpopulated debug points like the RX TX and GND visible towards the right, but the connection to the left actually had populated headers and that was a surprise.

I was encouraged by what I’ve seen so far. It all looks nice and tidy. If I can figure out the thermal problem, I should be able to restore this to full function with a new sealed lead-acid battery. Either way, the degraded battery needed to be removed. This was when I learned the foam padding was glued to the battery. I had hoped they could be easily transferred to a replacement battery, but sadly not.

Once the battery was removed it became much easier to move things around to get a better look. The temperature sensors are likely thermistors, and they have been held into a channel on the heat sink with some kind of glue that dried into a white blob. I had hoped maybe a sensor is misplaced, or dislodged, or unplugged, but it was none of those obvious problems. With those easy fixes ruled out, my prospect for repair dropped.

And once I flipped up the power PCB, my willingness to figure out the temperature problem also dropped. While one side was nice and tidy, the back side is a mess. I see lots of extra solder tinned to various areas on the circuit board, presumably to increase electric current capacity by some amount. And there’s some kind of white residue left all over the board presumably from soldering flux.

A quick web search found that this “heaps of solder” approach is not unusual for lowest-bidder circuit boards. Supposedly it is not terribly effective, but it does provide some benefit for nearly zero additional cost and thus sometimes chosen over any other “right way” approaches to solve the problem.

Not knowing the design constraints placed upon the engineers behind this product, I shouldn’t criticize. After all, it has worked well for over two and a half years. However, it doesn’t make me terribly fond of the device and given that the trivial fixes have been ruled out, repairing it has dropped very low on my priority list. Heck, let’s just say it has been removed from the priority list entirely.

Focus thus shifted from “evaluation for repair” to “satisfy curiosity and evaluate parts salvage.” Looking around the messy circuit board some more, I see the brains of the operation: the STM32F030K6 is a 32-bit ARM Cortex-M0 microcontroller, a cousin of the chip used in the “blue pill” development boards. Unsurprisingly, it is right next to the populated debug header pins I noticed earlier, though the traces don’t seem to go directly into the chip.

Looking past the power control PCB, I see another circuit board. Ah, yes, we would certainly need another board for the front panel status display, and on/off buttons.

Unplugging a few wiring harnesses gave us a better look.

The brains of this operation is a less powerful 8-bit chip, the STM8L052C6.

To give myself a little more room to work, all connectors to the power control PCB has been removed.

But it’s still too cramped, so I also removed the handle. This is a very sturdy handle that is also comfortable to hold. Attached with not just six screws but also molded-in channels to take up weight from the front and rear enclosure halves. Usually when I tear down retired products for salvage, the non recyclable plastic is sent to the landfill. But this time I’m looking at a sturdy enclosure with a handle and think there may be a second life for them.

Finally the control PCB is freed.

Not too many immediate candidates for salvage on the back side.

But the front is a different story. Multiple buttons and LEDs, plus four jacks. Two of them are common 5.5mm OD / 2.1mm ID barrel jacks, the other two are less common but matches the size used by Lenovo for some devices. Piezo buzzer, USB ports, all kinds of good stuff. I doubt I’ll find another use for the LCD panel, though.

I’m still very wary of 110V AC, but these sockets are so easy to salvage I might as well do so. I’m amused at the fact the grounding prong is left unconnected. A portable power source is not connected to ground, so of course there’s nothing to connect them to, but it’s still funny to see.

The 12V “cigarette lighter” socket is very likely to find another use. I wanted to salvage this connector but it was not obvious how. It took me a while to figure out what I was looking at, the answer is that the entire outer base is the “nut” holding the socket in place. In order to remove it from the panel, I had to turn the whole exterior counter-clockwise. And before I could do that, I had to break away most of the solidified orange adhesive.

Nonstandard size meant I had to dig through the tool box for pliers and vise grips of the right sizes to grip without crushing the thin metal exterior can. But eventually it was freed, and the socket could be removed from the panel.

Using earlier pictures as reference, I plugged all the electrical connectors back where they were. Then the mechanical components were laid out for this final roll call without the battery.

Out of all the electronics, I believe the cooling fan will be the first to find a use somewhere, followed by the 12V socket. But I’m actually more intrigued by the enclosure. It is sturdy, already designed to carry something heavy, has provision for cooling, has a big confidence-inspiring handle, and soft rubber feet cushions impact when I set down the box. I think I will cut away the front panel and replace it with something 3D-printed or laser-cut, and the rest of the… whatever it will be… can be installed inside the box. There are lots of potential here.

APC RBC Battery Module Teardown

I have a few UPS (Uninterruptible Power Supply) units to keep my electronics running through short blinks in household electricity, something more likely in a heat wave as neighborhood air conditioning units demand power from the grid. Historically I’ve preferred UPS made by APC as they’ve worked well for me, but over the past few years I’ve heard grumblings from unhappy APC users. The claim is that quality of their consumer line has gone down since their acquisition by Schneider Electric in a misguided effort to compete on price. I can confirm the price premium is less than it used to be, but it still exists. And as to the quality… all I can say is that my units are still working. I’ll post an update if any of the newer APC units fail.

I saw some of the complaints were of dead lead-acid batteries after some years, but I do not consider that a failure on APC’s part. Just like the lead-acid batteries in our cars, batteries are wear items expected to need replacement after some number of years. The guidelines for mission-critical UPS is to replace the battery modules after 2-3 years of active service, but that is being cautious. Batteries on long term standby (like those in a UPS) can last much longer. It’s just a matter of luck.

My luck ran out after five years, when my UPS started beeping at me with an error code. I bought the official replacement battery APCRBC123 (*) but I was curious: Superficially it appears to be two commodity 7Ah 12V modules connected together, are they actually that? Once the new module was installed and working, I took the old module outside to see if my suspicion was correct. The modules were held together by plastic sheets with adhesive backing, complete with convenient tabs where I could start peeling.

Once tape was removed (surprisingly cleanly) I could split the module apart and see it is indeed a pair of commodity form factor lead-acid batteries. Two of them, connected in series via a proprietary adapter in the middle.

So now I know: for the next replacement, it is possible to buy commodity batteries and rebuild the module myself. It wouldn’t have saved me much money this time: the APC module costs roughly in line with the average selling price of two 7Ah batteries. (*) Besides, who knows how long those zero review lowest-bidder batteries would last. But in a few years my new battery module will wear out and require another replacement. If there is a significant price premium on authentic APC replacement modules — or if they are no longer available at all — I have a fallback option.

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