HP Stream 7 Hardware Internals

I opened up my HP Stream 7 because I wanted to see if I could run it without the battery. The answer is no, but since I had it open anyway it is an opportunity to look over the mechanical design of this little tablet. The general electrical architecture is not surprising, similar to most tablets majority of interior volume was allocated to the battery and a PCB smaller than the battery held most of the electronics.

The mechanical engineering, however, showed evidence of more attention than I would have expected in an entry level design that must have been designed for cost. The rearmost removable plate to access microSD slot was nothing special, but as soon as I started looking at the next layer I was impressed by how rigid it was with only a few clips and screws. This attention to mechanical design carried across a few other elements.

HP Stream 7 05 reinforcement plate

This metal plate had two of the enclosure screws dedicated to holding it in place. This plate is immediately adjacent to the micro USB power port and the headphone jack. It reinforces the part of the PCB most likely to see mechanical stress, reducing the chances that a clumsy user would tear out these plugs by accident. Unfortunately while the mechanical engineers did great work, somebody dropped the ball on the electrical front. The headphone jack is so noisy as to be unusable, a trait highlighted in reviews so I know it’s not just this unit.HP Stream 7 06 side switches

For the side buttons, I had expected to see sideways switches on the main PCB. I’ve seen those small surface mount buttons before and they are at risk of breaking if the mechanical design doesn’t redirect stress elsewhere. But they are cheap, so we keep seeing them, and they keep breaking off in poorly designed devices. But there’s no such cost-cutting shortcut for this stout tablet. Its buttons are on a separate PCB mounted such that it can take the force face-on instead of letting the force shear off a sideways switch. This adds parts count, and adds steps to assembly, which adds cost, in order to give us more durable buttons. I appreciate it.

HP Stream 7 07 solder and pads why

Behind the switch is this puzzling field of copper pads and solder. Pads and solder like this are usually for surface mount electronics components, but this large field is completely devoid of hardware. I have no idea why this is here or what it does.

HP Stream 7 08 flash sound touch display cable

Lower down we see a SK hynix chip with “NAND” label, presumably the onboard flash memory storage. Adjacent to that chip is the microSD slot where the user can add more storage. Adjacent to those chips I see the crab I associate with RealTek audio chips. Two flexible PCBs round out the bottom. One of these is probably for touch and the other for display.

HP Stream 7 09 speaker

At the very bottom, a small speaker that is actually quite sizable for such a tiny tablet, but there are fundamental handicaps to sound quality at such sizes. I’m thankful for the speaker, but I would have much rather have had a better headphone jack.

Overall I feel the mechanical design on this tiny tablet is pretty good. Too bad its electrical and computational performance isn’t up to the mechanical design. And after this little detour through the world of hardware design, I return to trying the ESA ISS Tracker on other machines. Next on the list: Samsung 500T.

HP Stream 7 Battery Disconnect Test

I dusted off my HP Stream 7 tablet to see if it might be suitable for an always-on status display. I encountered some battery power management issues and wanted to see if I could try running it without a battery. Every Windows x86 laptop I’ve ever owned was happy to run without battery power and since my current intent is for a wired 24×7 display screen, I didn’t need the battery anyway.

HP Stream 7 00 back plate intact

This experiment was made possible by the design of the device. Relative to almost every other piece of modern portable electronics, the HP Stream 7 is easy to open up. The back plate can be opened without tools, just follow the gap they designed and start prying plastic clips apart.

HP Stream 7 01 back plate removed

This was how users could access its microSD slot for adding more storage space. And given how the battery is clearly visible when the back is removed, I thought it was also to enable easy battery replacement. My assumption was wrong! The battery appears to be glued in place and WARNING: BATTERY IS NOT REMOVABLE printed on the battery. Curiously that was printed with a dot matrix printer, implying this specific battery is not always non-removable, perhaps it is removable from another device but that won’t help us here today anyway so let’s move on.

HP Stream 7 02 bashed corner

I don’t remember ever dropping this tablet, but one corner tells a tale of my neglect.

HP Stream 7 03 inner plate removed

If I want to try running this device without battery, I will need to access its battery connector which is hidden underneath the next piece of plastic. That piece is fastened quite well by a large number of plastic clips, backed up by small screws. Together they created a pretty durable enclosure for this tablet while still being removable. There was nothing tricky about opening up this device. Once the second back plate was removed, the battery connector was accessible.

HP Stream 7 04 battery is not removable

Once exposed the connector easily popped free. I pressed the power button and… nothing. Unlike laptops, this device refuses to run without a battery. This makes it less useful for the current project. Nevertheless, such ease of access to durable internals has raised my opinion of this tablet. And since I had it open, I might as well look around a little more.

LED Modules Salvaged From Cree Dimmable Bulb

Earlier this year I brought a failed dimmable Cree LED light bulb to SGVHAK for a teardown. We determined the LEDs were fine and the problem was in its power supply but we couldn’t figure out exactly where. I stashed the board aside, intending to someday pull the LED modules off for potential reuse elsewhere. That “someday” has finally rolled around.

Removing 10 LED module from light bulb

I deployed the heat gun I’ve used to remove many components from PCBs before. It is usually just for fun, or for removing hardy components like switches, transformer coils, and power connectors. This would be the first time I tried removing a silicon component with intention of reuse.


Out of eight modules, two were damaged when I tried to remove them. These LED modules were composed of two parts: a substrate to which the set of 10 LEDs were mounted, and a diffuser/cover module over them. And much to my chagrin – they weren’t bonded very tightly to each other. Here are pictures of one of the damaged modules. One LED was clearly torn off and embedded in the cover, or else I would have been tempted to power it up just to see if it works. (The LEDs are not powered in the picture, they appear bright via reflected ambient light.)

LED module with ruler

I considered trying to repair that module, by adding a blob of solder to bridge the gap where the damaged LED used to live. But it proved beyond my skill level to work at such sub-millimeter scales. Here is one of the successfully removed modules next to a ruler showing millimeters.

LED module with 3 soldered wires

There are three solderable contacts at the bottom of each module where I expected just two. So they would be positive, negative, and… something else? To try to figure out which pad did what, I soldered a small wire (trimmed from the end of a resistor) to each pad. This turned out to be even more difficult than its small size suggested. The first wire wasn’t too bad, but when I tried to solder on a second wire I understood the challenge. This module is so small there’s very little heat dissipation between adjacent pads. As soon as I heat up one solder joint, it is hot enough to melt solder on remaining pads too. This was really designed for SMD soldering by machine, where the solder is supposed to all melt at once. Soldering one at a time by hand was hard.

Once soldered, I connected power to two of the three pins. It appears the center solder point is not for power. My best guess is that it is for heat dissipation and apparently a wire soldered to the pad does not offer enough dissipation to tolerate abuse. As a test I cranked up the power (over 30V and over 40mA). That heated up the LED enough to melt the solder and escape, falling off the wires onto my workbench.

LED module with 2 soldered wires

Which meant another opportunity to practice patience while soldering. This time I didn’t bother soldering to the center pad, and I didn’t crank the power up as high.

LED module illuminated

These LED modules give a dull glow at 24V, drawing less than 10 mA while doing so. They start growing brightly at roughly 27V, drawing approximately 20mA. I’ll need to provide better heat dissipation, connected to that center pad, before I push through power any higher again.

Panasonic UJ-867 Optical Carriage (Briefly) Under A4988 Control

Once I extracted the optical assembly carriage of a Panasonic UJ-867 optical drive, the next step is to interface it with a Pololu A4988 driver board. And just as with the previous optical drive stepper motor, there are four visible pins indicating a bipolar motor suitable for control via A4988. However, this motor is far smaller as befitting a laptop computer component.

Panasonic UJ-867 70 stepper motor connector

The existing motor control cable actually passed through the spindle motor, meaning there were no convenient place to solder new wires on the flexible connector. So the cable was removed and new wires soldered in its place.

Panasonic UJ-867 80 stepper motor new wires

Given the fine pitch of these pins it was very difficult to avoid solder bridges. But it appeared to run standalone so I reinstalled into the carriage. Where it still ran – but was very weak. Hardly any power at all. When I tilted it up so the axis of travel is vertical, the carriage couldn’t win its fight against gravity. Since the job is only to move an optical assembly, I didn’t expect these carriages exert a great deal of force. But I’ve seen vertically mounted slot loading optical drives. I thought it should at least be able to fight against gravity.

A Dell laptop charger delivers 19.2V. I’m not sure how many volts this motor intended to run at, but 12V seemed reasonable. Then I increased current beyond the 50mA of the previous motor. Increasing both voltage and amperage seemed to help with more power, but it remained too weak to overcome gravity.

As I’m tilting the metal carriage assembly in my hand, I started noticing it was warming. Oh no! The motor! I checked the temperature with my finger, which was a mistake as it was hot enough to be painful to human skin. I shut down my test program but it was too late, the carriage never moved again.

Lessons learned: don’t get too overzealous with power and check temperature more frequently.

And if I want to continue these experiments, I’ll need another stepper motor assembly.

Panasonic UJ-867 Optical Drive Carriage Extraction

The Panasonic UJ-867 is a slot loading optical drive. This particular unit was salvaged from a dead Dell XPS M1330 previously featured when I pulled its power port, and disassembled its battery, plus trying to use its AC power adapter to charge a Neato vacuum. A web search indicated this drive was better known as a drive used in certain models of Apple MacBooks. An optical drive typically has a carriage for its laser assembly driven by a stepper motor, and that carriage is my target for further stepper motor experimentation.

Panasonic UJ-867 20 Norton inside

When the lid was removed, the age of this device was clear: it still held a disk! The Windows edition of Norton AntiVirus confirms this was not from a MacBook. The year also spoke to the vintage of this drive.

Panasonic UJ-867 30 mechanicals top

With the disk removed, we can see all the mechanical linkages. This was far more than I had expected, because I had never taken apart a slot-loading drive before. Many of the pieces were involved in the slot loading mechanism, which is in the “disk inserted” position. (The Norton disk was not properly ejected – I removed the lid and popped it off!) Various mechanisms in this position block fasteners making it difficult to take apart.

Panasonic UJ-867 40 eject motor

Tracing through the mechanical bits, I guessed this motor is the heart of the drive loading and ejection mechanism. It is a simple DC motor so I should be able to put power on these pins to move the mechanism to their eject state. However, there are a few parts nearby that I might bump into if I powered from the top, so to be safe I soldered some pins from the bottom.

Panasonic UJ-867 50 eject motor wired

Applying power to this motor did indeed run through the ejection sequence, even though I’ve already removed the disk. Now it became fairly straightforward to take apart the drive.

Panasonic UJ-867 60 eject motor gearbox

Almost all of the pieces are specifically tailored to this usage, making reuse unlikely. But I do enjoy seeing the eject motor gearbox run. This is a distraction, though. The optical carriage was the goal and that was removed for the next step: connecting it to my Arduino + A4988 test breadboard.

Linear CCD Sensor And Other Curiosities In A Fax Machine

For SGVHAK’s regular first Thursday of the month meeting for June, Emily brought in an old fax machine abandoned by the side of the road.

The plastic enclosure yellowing from age is not a surprise, but its heft was: it was far heavier than it looked. Judging by the collection of debris this machine had gathered, it had been left outdoors for some time. It was not a surprise when it failed to power on. Which is fine as we had no use for a fax machine and little interest in fixing it, but we were curious what was inside one of these anachronisms.

Most of this device’s mass came from a single beefy cast aluminum frame inside the machine. Select portions have been machined to precise tolerances. Why was this necessary? Emily hypothesized the robust frame was necessary to hold optical scanning components in precise alignment. The optical path was more complex than we had expected. Illumination came from a wide LED strip sitting under what looks like a glass rod slice lengthwise. It began to emit visible yellow-green light at roughly 15 volts (while drawing less than 200mA) and we cranked it as high as 20 volts (just under 500mA) but no further as we didn’t know the strip’s limits.

That light bounced off a few front surface mirrors before reaching the document, whose reflected light is picked up by yet more mirrors and finally a lens assembly that focused onto a sensor. A web search for TCD102D only found the first page of this device’s data sheet. But it was enough to tell us it was a line of 2048 photodiodes designed specifically for this purpose of scanning a line of a document scrolling past sensor optics.

For the output side of this device, there was a roll of thermal paper and a thermal image print head that worked much like the sensor in reverse: a line that heats a sheet of paper rolling past it to create an image. Digging below them both, we find the mechanical pieces making paper scroll. There was a stepper motor driving rollers for source document, and another stepper motor driving rollers feeding thermal paper for output.

Beyond the two stepper motors, few components had prospect for reuse though some (like the front surface mirrors) were kept for novelty. Unfortunately this disassembly also evicted an insect from its now-demolished home.

The biggest win was a lens assembly that formerly sat in front of the linear CCD. It has the right optical properties to be used as a small macro lens for an equally small cell phone camera. Emily plans to design and 3D print a bracket to hold this lens at the proper location and distance so we should see more close-up shots of small electronics components in the future.

Old Couch Teardown

And now, something a little different from the usual fare. Today’s teardown project has no electronics in it whatsoever. It is an exploration into an entirely different category of home consumer merchandise: furniture.

This old couch had been in service for several decades and long overdue for retirement. The default option was to treat it as bulk waste and call for pickup, but let’s see what we can learn from its deconstruction.

We start with seat bottom cushion which were easily removed. Some coins were found but there were little else of value trapped within. Too bad – we once found a lost cell phone in here, but not today.

Couch Teardown 02 - bottom cushion removal

Unlike the bottom cushions, this couch’s back cushions were attached and had to be cut off for disassembly.

Couch Teardown 03 - back cushions cut off

Each armrest cushion were held by four of these rivet-like structures, two inside and two outside of each armrest. It was easiest to cut fabric around each rivet than trying to unfasten them.

Couch Teardown 04 - armrest cushions

Those armrest cushions were the final pieces of soft padding material. Everything that remained are fabric and rigid structure.

Couch Teardown 05 - all soft padding removed

Fabric panel cutting started with the bottom-most sheet. This sheet is not typically visible, made of a thin and partially transparent material that is also very tear-resistant.

Couch Teardown 06 - tear resistant bottom

This sheet was fastened by staples. The decision was made to cut instead of pull to avoid staples flying everywhere possibly puncturing tires and feet.

Couch Teardown 07 - evil staples

Seat springs were visible once that bottom fabric panel was cut away. We’ll be back for those springs later. For now focus is still on removing pieces of fabric so we proceed to cut back panel.

Couch Teardown 09 - cutting back panel

We can see more of the wooden frame once the back panel was removed. These wood beams were surprisingly irregular in their dimension. Each segment might be a little wider or thicker than its neighbors. Not that a great deal of precision was necessary – pieces were held to each other with copious amounts of staples. This construction method does not demand dimension accuracy. It’s possible this flexibility allowed the couch to be built using scrap wood left from manufacturing other things.

Couch Teardown 10 - back panel removed

Cutting off the back panel also exposes these metal strips. These were used to cover up fabric seams. When installed properly, they are not visible and thus preferable to staples.

Couch Teardown 11 - fastening strips

With the removal of each fabric panel, the couch looks less and less like a couch.

Couch Teardown 12 - side panels cut off

Returning to the bottom, a bolt cutter helps cut off the springs. With the first cut I discover they are bent in a direction to support weight. This discovery was accompanied by reinforcement that it’s always good to stay back when cutting metal things to minimize chances of injury.

Couch Teardown 13 - cutting springs

By this point all loose fabric panels have been cut free, as has metal springs. Most of the remaining parts are wood and fabric glued to panels of wood. It is time for the reciprocating saw to make its entrance.

Couch Teardown 14 - all fabric panels cut off

A reciprocating saw made quick work of wood pieces. A few cuts, and the couch back is gone.

Couch Teardown 15 - seat back wood cut off

After a few more cuts, the couch is no longer recognizable as a couch at all. These easily managed pieces can now be disposed as regular household landfill and do not require special bulk waste procedures.

Couch Teardown 16 - no longer recognizable as couch

Household Light Switch Teardown

As a change of pace from tearing down consumer electronics, today’s teardown is a simple single-pole, single-throw household light switch. This specific switch has been in service for many years and failed with the following symptoms: mechanically, the switch now moves freely without the tactile feedback it formerly had. Electrically, the switch is always closed leaving the attached ceiling light fixture illuminated. These switches are simple and failures are rare, so it was interesting to find out what the weakest point was in such a simple thing.

The top mounting bracket appears to be made from stamped sheet metal, and held to its body with a few bent metal fingers. A pair of pliers released those fingers and we could see the next layer.

Light switch 2

We see a sheet of something that feels like paper. The most obvious purpose is for electrical insulation, but it may have some fire resistant properties as well. This sheet was easily removed.

Light switch 3

As soon as that sheet was removed, we had our first hint: a loose spring sitting in the lower left corner which probably should be sitting somewhere else.

Light switch 4

Lifting the switch lever showed us the nub that used to be that spring’s home. The spring served as an elastic connector between the the plastic lever flipped by the user and the metal contact beneath which closes the electrical connection. When the spring broke, there is no longer any physical connection between these two parts, and the metal contact stayed closed due to gravity.

Light switch 5

The spring broke off leaving approximately 2mm on the swinging metal contact. There’s a chance that, if we removed the small tail, we could reassemble the switch and it will work again. However, by this time a replacement had already been purchased from the local Home Depot for $0.88 USD and installed. The replacement is not exactly identical due to literal decades separating them, but the basic principles are the same. It’s amazing all of the following could be manufactured, built, shipped and stocked locally for retail sales all for just $0.88.

Parts list:

  • Sheet metal:
    • Mounting bracket.
    • 3 ~1mm thick metal pieces for electrical contacts.
    • 2 thin sheets keeping the two static electrical contacts inside body.
  • Fasteners:
    • 2 screws to mount wire to electrical contact.
    • 1 screw to mount ground wire.
    • 2 screws to mount bracket to electrical box.
    • 2 screws to mount cosmetic faceplate.
  • Misc. metal pieces:
    • 1 spring (the part that failed)
  • Paper:
    • 1 insulator
  • Plastic:
    • 1 switch toggle
    • 1 switch body

Original NEC VSL0010-A VFD Power Source

Now that we have a better understanding of how a NEC VSL0010-A vacuum fluorescent display (VFD) works, figuring out its control pinout with the help of an inkjet power supply, we returned to the carcass we salvaged that VFD out of. Now that we knew each pins’ function, we picked those that supplied 2.5V AC for filament power to track. We expect they are least likely to pass through or be shared by other devices. We traced through multiple circuit boards back to the main power transformer output plug. We think it’s the two gray wires on the left side of this picture, but our volt meter probes are too big to reach these visible contact points. And the potential risk of high voltage made us wary of poking bare wires into that connector as we did for the inkjet power supply.

NEC VSL0010-A VFD Power Supply - Probes Too Fat

Our solution came as a side benefit of decision made earlier for other reasons. Since we were new to VFD technology, our curiosity-fueled exploratory session was undertaken with an inexpensive Harbor Freight meter instead of the nice Fluke in the shop. Originally the motivation was to reduce risk: we won’t cry if we fry the Harbor Freight meter, but now we see a secondary benefit: With such an expensive device, we also feel free to modify these probes to our project at hand. Off we go to the bench grinder!

NEC VSL0010-A VFD Power Supply - Probes Meet Grinder

A few taps on the grinding wheel, and we have much slimmer probes that could reach in towards those contacts.

NEC VSL0010-A VFD Power Supply - Probes Now Thin

Suitably modified, we could get to work.

NEC VSL0010-A VFD Power Supply - Probes At Work

We were able to confirm the leftmost pair of wires, with gray insulation, is our 2.5VAC for VFD filament. The full set of output wires from this transformer, listed by color of their insulation, are:

  • Gray pair (leftmost in picture): 2.6V AC
  • Brown pair (spanning left and right sides): 41V AC
  • Dark blue pair: (center in picture) 17.2V AC
  • Black pair (rightmost in picture): 26.6V AC

There was also a single light-blue wire adjacent to the pair of dark blue wires. Probing with volt meter indicated it was a center tap between the dark blue pair.

NEC VSL0010-A VFD Power Supply Transformer

Once determined, we extracted the transformer as a single usable unit: there was a fuse holder and an extra power plug between it and the device’s AC power cord. We’re optimistic this assembly will find a role in whatever project that VFD will eventually end up in. 2.6V AC can warm filament, rectified 26.6V AC should work well for VFD grid and segments. And with proper rectification and filtering, a microcontroller can run off one of these rails. It’ll be more complex than driving a LED display unit, but it’ll be worth it for that distinctive VFD glow.

HP Inkjet Printer Power Supply For NEC VSL0010-A VFD

One of the reasons LED has overtaken VFD in electronics is reduced power requirements. Not just in raw wattage of power consumed, but also the varying voltage levels required to drive a VFD. The NEC VSL0010-A VFD whose pinout we just probed ran on 2.5V AC and ~30V DC. In contrast, most LED can run at the same 5V or 3.3V DC power plane as their digital drive logic, vastly simplifying design.

We didn’t have a low voltage AC source handy for probing, so we used 2.5V DC. We expected this to have only cosmetic effects. One side of our VFD will be brighter than the other, since one side will have a filament-to-grid/element voltage difference of 30V but the other will only have 27.5V.

But putting 2.5V DC on the filament occupied our only bench power supply available at the time. What will we use for our 30V DC power source? The answer came from our parts pile of previously disassembled electronics, in this case a retired HP inkjet printer’s power supply module labeled with the number CM751-60190.

HP CM751-60190 AC Power Adapter

According to the label, this module could deliver DC at 32V and 12V. Looking at its three-conductor output plug, it was easy to come to the conclusion we have one wire for ground, one wire for 32V, and one wire for 12V. But that easy conclusion would be wrong. Look closer at the label…

HP CM751-60190 AC Power Adapter pinout

We do indeed have a ground wire in the center, but there is only one power supply wire labelled +32V/+12V. It actually delivers “32 or 12” volts, not “32 and 12” volts. That last pin on the left has an icon. What did that mean? Our hint comes from power output specifications: +32V 1095mA or +12V 170mA. We deduced this meant the icon is a moon, indicating a way to toggle low-power sleep mode where the power supply only delivers 12V * 170mA = 2 watts vs. full 32V * 1095mA = 35 W.

With that hypothesis in hand, it’s time to hook up some wires and test its behavior.

HP CM751-60190 AC Power Adapter test

When “sleep mode” pin is left floating, voltage output is 32VDC. When that pin is grounded, voltage output drops to 12VDC. Since we’re looking for 32VDC to drive our VFD grid and elements, it’s easy enough to leave sleep wire unconnected and solder wires to the remaining two wires to obtain 32V DC for our VFD adventures.

HP CM751-60190 AC Power Adapter new wires

Sleuthing NEC VSL0010-A VFD Control Pinout

Vacuum Fluorescent Display (VFD) technology used to be the dominant form of electronics display. But once LEDs became cheap and bright enough, they’ve displaced VFDs across much of the electronics industry. Now a VFD is associated with vintage technology, and its distinctive glow has become a novelty in and of itself. Our star attraction today served as display for a timer and tuner unit that plugs into the tape handling unit of a Canon VC-10 camera to turn it into a VCR. A VFD is very age-appropriate for a device that tunes into now-obsolete NTSC video broadcast for recording to now-obsolete VHS magnetic tape.

Obviously, in this age of on-demand internet streaming video, there’s little point in bringing the whole system back to life. But the VFD appears to be in good shape, so in pursuit of that VFD glow, salvage operation began at a SGVHAK meetup.

NEC VSL0010-A VFD Before

We have the luxury of probing it while running, aided by the fact we can see much of its implementation inside the vacuum chamber through clear glass. The far right and left pins are visibly connected to filament wires, probing those pins saw approximately 2.5V AC. We can also see eight grids, each with a visible connection to its corresponding pin. That leaves ten pins to control elements within a grid. Probing the grid and element pins indicate they are being driven by roughly 30V DC. (It was hard to be sure because we didn’t have a constant-on element to probe…. like all VCRs, it was blinking 12:00)

This was enough of a preliminary scouting report for us to proceed with desoldering.

NEC VSL0010-A VFD Unsoldering

Predating RoHS solder that can be finicky, it was quickly freed.

NEC VSL0010-A VFD Freed

Now we can see its back side and, more importantly, its part number which immediately went into a web search on how to control it.

NEC VSL0010-A VFD Rear

The top hit on this query is this StackExchange thread, started by someone who has also salvaged one of these displays and wanted to get it up and running with an Arduino. Sadly the answers were unhelpful and not at all supportive, discouraging the effort with “don’t bother with it”.

We shrugged, undeterred, and continued working to figure it out by ourselves.

NEC VSL0010-A VFD Front

If presented with an unknown VFD in isolation, the biggest unknown would have been what voltage levels to use. But since we have that information from probing earlier, we could proceed with confidence we won’t burn up our VFD. We powered up the filament, then powered up one of the pins visibly connected to a grid and touched each of the remaining ten non-grid pins to see what lights up. For this part of the experiment, we got our 32V DC from the power supply unit of a HP inkjet printer.

We then repeated the ten element probe for each grid, writing down what we’ve found along the way.

NEC VSL0010-A VFD Annotated

We hope to make use of this newfound knowledge in a future project, and we hope this blog post will be found by someone in the future and help them return a VFD to its former glowing glory.

Examining Neato XV-12 Charging Dock

When [Emily] found her Neato vacuum in a thrift store, it had an advantage over mine in that hers still have the company of its charging dock. This is our first look at a Neato robot vacuum charging dock and a chance to determine how one worked. We wanted to have some idea of what to expect when we put it to work charging newly installed replacement batteries.

Neato charging dock front

The charging dock is designed to sit against a wall. The two metal strips are obviously for supplying power, as they line up with the two metal wires at the back of a Neato vacuum. When the dock is plugged in, a volt meter reports 24V DC between those two plates, top plate positive and bottom plate ground. Each of the plate is mounted on a piece of spring-loaded plastic that allows approximately 3-5mm of horizontal movement. A Neato vacuum can press its wires against these plates to draw power.

Above the plates is a black plastic window, we expect something behind that window to communicate with the Neato so a hungry robot vacuum knows where to go to feed itself. How does it work? We hypothesized there are infrared emitters and receivers behind that panel, functioning like a consumer electronics remote control, to talk to a Neato vacuum.

Neato charging dock back.jpg

Neato charging power adapterThe orange tab on top looked very inviting as a way to open the dock. A bit of fiddling later, the dock was open. It was surprisingly simple inside. There was an AC power supply delivering 24V DC. It has a standard power cable on the input side, which can be routed to exit either side of the dock. This way a user can swap as needed to point towards the nearest power outlet, and possibly swap for a longer standard power cable if necessary to reach an outlet. The output wires of the power supply lead to the two metal plates, and that’s it.

Surprisingly, there’s nothing visible behind the black plastic window. The IR emitters and receivers we expected were absent, as were any circuit boards with components to communicate with the vacuum. So this charger dock location beacon must work passively. Now we’re really interested in finding out more. How does it work?

The black plastic window were held in place with a few clips. They stood between us and knowledge and were quickly dispatched. We were afraid the black plastic might be glued in place, but fortunately that was not the case and it popped off for us to see underneath.

Neato charging dock mystery panel demystified

We see a pattern laid out with two types of surfaces. The white segments are highly reflective much like the stripes on high visibility orange safety vests. The black segments are presumed to provide a contrast against the white parts. We found out earlier that a Neato lidar data stream returns both distance and intensity of reflections it saw. The distance is useful for navigation, but using just distance information the charger would be an unremarkable flat surface. This is where intensity comes into the picture: these surfaces behind the black plastic window will create a distinct pattern in reflection intensity, something a Neato robot vacuum can seek to find its charging dock.

Disassembling this passive system tells us two things:

  1. The engineers are Neato are quite clever
  2. We now know enough to try creating our own charging docks. Userful when we have Neato vacuums found at thrift stores without their charger.

Before we tackle new projects, though, let’s see how a full Neato system works in practice.

AltoEdge Infinity USB Foot Pedal Dates Back Before Windows 7

This SGVHAK teardown project came courtesy of an electronics waste bin. A nondescript box with a USB cable, it has three moving parts on top of a heavy base. The center piece takes up majority of width, and two far smaller pieces sitting on either side. Each piece can be pressed down and we can feel a tactile click of a switch. It has a respectable heft and doesn’t look damaged or even worn. It feels rather beefy and unlikely to physically break.

Infinity Foot Pedal IN-USB-2

A label on the bottom of the device lets us know it is version 14 of the Infinity IN-USB-2 foot pedal. Which explains its mass and durability: this box was designed to sit under a desk and be stepped on. A box sitting out of sight explained its raised side pedals allowing its user to find them by feel.

Infinity Foot Pedal IN-USB-2 v14 label

A few screws on the bottom held a plate in place, easily removed. We see a few springs for the pedals, and two pieces of metal that gave the device its heft.

Infinity Foot Pedal IN-USB-2 bottom panel removed

There were a few visible plastic clips holding individual pedals in place, but they were only the first line of defense – unclipping them allowed individual pedal to move a little further but did not release them. There were also a few hinge pins that could be removed, but again it allowed additional movement but did not release.

The two shiny metal weights were held by tenacious stretchy glue. We could pry them up far enough to see they weren’t obviously hiding screws, but we were wary to apply addition force as it threatened to break apart the plastic housing.

Without an obvious way forward for nondestructive disassembly, we decided to pause and reassemble the pedal to see if it can be useful intact before we risk destroying it. My computer was running Ubuntu at the time, which gave us a starting point with the dmesg tool to see what kind of greeting it has to say to my computer.

[ 459.086214] usb 1-4.4.3: new low-speed USB device number 17 using xhci_hcd
[ 459.192673] usb 1-4.4.3: New USB device found, idVendor=05f3, idProduct=00ff
[ 459.192679] usb 1-4.4.3: New USB device strings: Mfr=1, Product=2, SerialNumber=0
[ 459.192683] usb 1-4.4.3: Product: VEC USB Footpedal
[ 459.192687] usb 1-4.4.3: Manufacturer: VEC
[ 459.196360] input: VEC VEC USB Footpedal as /devices/pci0000:00/0000:00:14.0/usb1/1-4/1-4.4/1-4.4.3/1-4.4.3:1.0/0003:05F3:00FF.0012/input/input28
[ 459.196980] hid-generic 0003:05F3:00FF.0012: input,hiddev1,hidraw9: USB HID v1.00 Device [VEC VEC USB Footpedal] on usb-0000:00:14.0-4.4.3/input0

So far everything looks in line with the manufacturer’s name we found earlier. It also tells us the device conforms to USB HID (Universal Serial Bus Human Interface Device) specification. The final line also hinted us to a newly visible device under the path/dev/hidraw9.

$ ls -l /dev/hidraw9
crw------- 1 root root 240, 9 Mar 17 13:32 /dev/hidraw9

This path is owned by root, so further experimentation requires taking ownership of that path to see what we can do with it.

$ sudo chown $USER /dev/hidraw9

Now we can try treating it as a file with the cat command. Every time we press or release a pedal we get some kind of visual feedback but we don’t understand it.

cat dev hidraw9

We then tried treating it as a serial port using minicom but that didn’t get us much further. It vaguely resembles the garbage that might occur if a baud rate setting is incorrect, but changing baud rate in minicom didn’t do anything. Probably because it’s not a serial port!

Since the device was classified as a USB HID v1.00 Device, the next thought was to try communicating with it via some sort of HID API for developers. But USB HID is not a trivial thing and after a half hour of following and reading links to documentation I was no closer to talking to the pedal in a “proper” way. So I tabled that approach and returned to treating it as a file. It’s pretty trivial using Python’s file APIs to open it up for reading.

>>> hr9 = open('/dev/hidraw9','r')

Reading a few bytes at a time, we figured out the device sends two bytes upon every action. First byte is a bitfield indicating pedal status, and the second is always zero. The leftmost pedal corresponds to the least significant bit 0x1, then center pedal 0x2 and right pedal 0x4. So if both right and center pedals were both pressed, it would give 0x6. Here’s a simple Python loop that reads two bytes at a time and outputs to command line.

>>> while True:
... hr9.read(2)

The output if I press and release the left, then repeat for center and right pedal.


Not every action will trigger data events. There’s a small time window where separate events are collapsed together for a single notification. If I’m quick enough on the press and on release, I can push the right and left pedals simultaneously for a single 0x05 report, then release simultaneously for a 0x00 report, without any intermedia reports of 0x04 or 0x01.


This is a very promising set of experiments indicating that, if it should be necessary, we can write code to make use of this pedal in Linux without digging through all of HID API.

With that knowledge under our belts, experimentation then moved to Windows 10, which immediately recognized it as a USB HID and even shows us the name. However, it doesn’t do much without further help.

VEC USB Footpedal device is ready

Searching for answers on the web, we learned this device was designed for people transcribing audio recordings into text. The pedals allow them to control sound playback (pause, play, rewind, etc.) without taking their typing hands off the keyboard. I’m sure this is a productivity boon for its target audience, but that wasn’t us. Fortunately, the manufacturer has also released a piece of software call Pedalware which will allow this pedal to be used outside its designed scenario, like emulating keyboard keys or mouse buttons. I thought it sounded interesting enough to try.

And this is where we started getting a hint why this device has been retired… this piece of hardware’s associated software is old. Pedalware’s installer demands Windows 7 or earlier and refused to run under Windows 10.

Pedalware needs Windows 7 or earlier

At this point, Windows 10 backwards compatibility module kicked in and offered the option of running in compatibility mode. I accepted.

Pedalware needs Windows Vista compatibility mode

That was enough to get Pedalware up and running on my Windows 10 computer. Now I can assign an arbitrary keyboard or mouse action to each of three pedals.

Pedalware up and running

This worked fine in everyday web browsing and productivity applications. It is, however, too slow for gaming purposes. The aforementioned time window seen under Linux, which collapsed multiple events into a single event, manifests here as well resulting in foot click actions getting lost in high-speed gaming action.

But that’s fine, the device was never intended to be a gaming peripheral. The real problem comes from its driver software becoming unreliable as a computer goes into low-power standby. When the computer resumes, the pedal doesn’t always come back into action. And once it gets stuck, the only way to get it back is a full reboot.

This was a sign of the times when this device was designed. I remember when many peripherals would not gracefully handle a computer going to sleep, which meant I typically leave my computer running in the Windows XP/Vista/7 days. Computers have gotten more power efficient over these years but it’s still better to put them to sleep. Also, modern USB peripherals are much better about resuming from sleep.

But this pedal does not, and that’s probably why it was retired. Fortunately, my work does not require a predictably functional foot pedal, so I’ll keep it around and try using it on the occasions when it works.

Cree Dimmable LED Bulb Teardown

I brought an old LED light bulb to a SGVHAK meetup for an educational dissection. This bulb has illuminated my front porch for several years, hooked up to a light-sensitive fixture that turns on the bulb when dark, and turn it off when the sun is up. However, when illuminated this bulb has started flickering. At first it was a mild pulse that I didn’t mind very much as I don’t usually need the light myself anyway. But after a while, the blinking started getting annoying and even the bright pulses were too dark for the light to serve its intended purpose. This bulb was retired, and now we take it apart to see what’s inside.

Looking inside the cooling vents, we can see there are two circuit boards mounted at right angles to each other. Obviously there will be LEDs soldered to these boards, with a power supply at its base. Since all the LEDs pulsed together, we expect there to be a power supply failure and hope we might be able to see what component caused the problem.

Here’s the bulb intact, before teardown began.

Cree LED bulb teardown 1 - intact

Here’s the label on the bulb. This was not a bargain basement device, it was a dimmable bulb and it was also designed to be usable in damp environments as the front porch is occasionally exposed to rain. It was also exposed to outdoors wildlife, including some insects who have climbed inside and sadly died there, too.

Cree LED bulb teardown 6 - label

It was nicely sealed with no obvious way to take apart the plastic housing nicely, so out came a beefy cutter and we start cutting from top vents.

Cree LED bulb teardown 2 - first cut

Once the top vents were clipped open, we could perform some literal debugging of our device by pouring the dead carcasses out. They look like honeybees.

Cree LED bulb teardown 3 - pour out the bugs

Aside from debugging, the opened top also lets us see more details inside. Sadly, there were no visible mechanisms for easy release, so cutting continues at waist-level vents.

Cree LED bulb teardown 4 - second tier cut

Once those portions were cut away, we could see more of internals. There were fewer LED surface mount packages than we had expected.

Cree LED bulb teardown 5 - second tier removed

At this point I ran out of convenient places to cut with a hand tool, so cutting moved on to a band saw.

Cree LED bulb teardown 7 - band saw

Once the band saw cut through all around the base of transparent plastic bulb exterior, we were able to free its internals for a closer look. Surprisingly, the circuit boards connect to each other and to the base with tiny spring-loaded connectors rather than a direct soldered joint. One hypothesis is the bulb was not only designed for humid environments, it was designed to sustain vibration as well. Another hypothesis was that humid environments also imply a larger temperature swing, where spring-loaded connectors can accommodate thermal expansion/contraction better than soldered joints.

Cree LED bulb teardown 8 - disassembled

Here is the main board’s topside. Nothing appeared obviously damaged. The big electrolytic capacitor immediately drew our attention, as that is the type of component most likely to fail with age. However, the usual signs were absent. No leaking electrolyte, no bulging of the body, and no breakage in the top. With the help of our multi meter, we could tell the capacitor has neither failed open or failed short. We also measured its capacitance, which won’t be a reliable number as the capacitor is still installed on the board: we’d be measuring capacitance of the capacitor as well as the board it is installed on. But the number was roughly in the ballpark of the rating printed on its side, so it looks clear on all counts.

Cree LED bulb teardown 9 - main board front

Bottom side of the main showed no such obvious attention-getters. The small light colored surface mount component at the base might be a safety fuse, and it tested OK for continuity.

Cree LED bulb teardown A - main board back

We explore the fewer-than-expected LED modules by trying to power up a single LED using a bench top power supply. At first it stayed dark and we thought maybe the LEDs were at fault instead of the power supply. But then we realised we weren’t giving it enough power: we were surprised it took over 24 volts before a single module would illuminate.

Cree LED bulb teardown B - LED needs 24V

An explanation surfaced once we adjusted camera settings to see individual light sources inside the package: there are actually ten LEDs in each package, in a three + four + three configuration. This explains how it could be so bright with so few surface mounted modules!

Cree LED bulb teardown D - ten LED per package

At this point we’ve verified all the discrete components we understood and could test, we’ve removed dead bug remains that might have caused problems, and we cleaned up all the electrical connectors. Maybe that’s enough to bring this bulb back to life?

Cree LED bulb teardown C - back on 110V AC

Sadly, the answer was no. We hooked it up to AC power and plugged it in: it is still dim and blinky. Obviously we failed to understand how this particular bulb works – the power supply circuitry was far more complex and sophisticated than we had expected. But still, it was fun to look inside a premium (for its day) LED bulb.


Disney Infinity Base and Figurine Teardown

On the one hand, I love many Disney properties. On the other, I’m very clear Disney wrings every penny out of their fans. Disney Infinity was a video game where new characters and capabilities are acquired via purchase of physical figurines. Advancement in the game requires a steady stream of new figurine purchases. As much as I love both video gaming and Disney properties, that was too much of a money grab for me to put up with. Apparently enough people thought the way I did, because Disney shut it down for not making enough money.

Ironically, that announcement is why I now have a Disney Infinity starter pack: once the announcement was made, these kits went on the clearance rack for drastically reduced prices. I was not interested in paying their full price, but I can certainly spare $5 for a gaming peripheral with no future just so I could take it apart! It took a while for me to get around to this project, which finally happened at a recent SGVTech meetup.

Disney Infinity 1 intact

This starter pack came with the system base, Merida, and Stitch. Based on how the game worked, we expected a RFID-based system. That implies RFID chips in the bottom of these figurines, and the USB-connected base has coils to read them. Expectations on these fronts were met but there were a few surprises on the way.

The plastic top of the base were held with a few clasps that were easily broken. Once removed, we could see three white PCBs each with what appears to be a surface mount LED on top, and a green PCB with connections to each of them and the USB cable.

Disney Infinity 2 top removed

When we flip over one of the white PCB, we could see it is a simple single layer design and its RFID coil is visible. The straight lines towards the middle are for driving the LED.

Disney Infinity 3 rfid pad flipped

The control board is a more typical multi layer board. The biggest chip on board is from the STM32 family, specifically the STM32F072C8T6. Typing the numbers printed on top of next two larger chips into a web search didn’t return any useful results.

Disney Infinity 4 STM32 in charge

The LED on each white PCB appears to have four leads. When we saw four leads our first thought was an addressible LED with power, ground, data, and clock. Then we remembered this is a toy built to low cost: it’s more likely a RGB LED package with a common anode and three cathodes, one per color. Either that or the reverse with a common cathode and three color anodes. The ‘+’ labelled on its PCB hinted at a common anode design, which was confirmed with a quick test using a bench power supply putting power on some exposed pads.

Disney Infinity 5 pad LED illuminated

Aside from the RGB LED, there’s not much of interest from these three white PCB I could pull off and reuse. The main green PCB was more sophisticated, and there were exposed pads on the bottom that hint at the possibility of reprogramming the STM32 for something fun, but that’s beyond my current skill level. (This guy can probably do something with it.) The part of the board with best potential for reuse is its USB connection. It gives me a USB-A connector for plugging into a computer, and the other end is a nice modular connector with 2mm pitch. This will be useful the next time I want to hack a standard USB cable onto a device.

Attention then turned to the other part of this system: the figurines. Once the clear plastic portion was removed, its RFID sticker is accessible. Sadly, Stitch’s arms did not survive the process of prying apart his base.

Disney Infinity 6 Stitch sticker removed

A closeup of RFID sticker showed most surface area is antenna, and that tiny black dot is a chip with the secret code to unlock a Stitch character in a Disney Infinity game. People online have tried to hack these bases with little success. Given that the revenue stream comes from selling figurines, there was a robust security scheme to protect the game against counterfeit tags. I was not interested in exploring the digital side in any case, this was strictly a physical teardown.

Disney Infinity 7 RFID sticker closeup

In her movie Brave, Merida was guided by little blue glowing wisps. In the figurine, a wisp floated by Merida’s foot. As a ghostly entity, it was fittingly cast in translucent plastic.

Disney Infinity 9 Merida wisp top

But there was an extra detail: the translucent plastic went all the way through the opaque parts of the stand, so it could pick up LED illumination from the USB base. When it glowed with a blue LED, the wisp would glow blue just like in the movie. This bonus showed the artists were thinking about how to best take advantage of this medium. Too bad such creative thoughts were infrequent (Stitch had no such attraction) and probably went unnoticed by most buyers.

Disney Infinity 8 Merida wisp bottom

The final piece – hexagonal tiles for some purpose or another – were unremarkable. Once the transparent and opaque pieces were pried apart, a similar RFID tag could be removed. I didn’t see any interesting possibilities for reuse.

Disney Infinity A Merida hexagon

Waterpik WF-03W / WF-03C Teardown

My project at last night’s SGVTech meet was to dig into a nonfunctional cordless water flosser, the Waterpik WF-03. I added this to my evening tooth brushing & flossing routine upon recommendation of my dental hygienist, and it worked for several months before it stopped running. At first I thought it just needed new batteries, but when I opened the watertight battery compartment, out poured brown water along with the three AA batteries. Clearly something has failed inside the device.

Waterpik WF-03 intact

There were no obvious ways to disassemble this device, which I’m sure is partially motivated by a desire to control water intrusion. Given the high potential for disassembly to be a destructive process, it’s not realistic to expect I could repair the device and return it to service. But somewhere inside is a battery-powered water pump designed to deliver short high pressure pulses, and I am confident I can find a fun use for such a device in the future.

The first thing I tried was prying off the silvery front panel. I had hoped maybe it was held by clasps, but it was clearly glued in place. I had also hoped there would be fasteners visible below this panel, but no luck. The only visible part is the switch controlling high/low/off operation.

Waterpik WF-03 front panel removed

Prying at various places of the plastic enclosure by hand, the only parts that moved at all were near the bottom, flanking either side of water resorvoir. I started prying by hand and, when that wasn’t enough, moved on to a screwdriver.

Waterpik WF-03 base disassembly 1

Looking at the seams I broke apart with the screwdriver, the plastic components are either glued or welded together. There’s definitely no turning back in this disassembly. Once the screwdriver pried a few pieces of plastic open, I could enlist the use of pliers to continue pulling plastic apart.

Waterpik WF-03 base disassembly 2

Once I could see enough into the interior to have a good idea where a cutting blade could do some good, a hack saw was enlisted to finish the job.

Waterpik WF-03 base disassembly 3

Once the front outer shell is cut all the way around the base, the mechanical guts slides out easily.

Waterpik WF-03 base released 1

Waterpik WF-03 base released 2

There’s a smaller piece of enclosure on the back, designed for the water reservoir to slide and clip into. Removing this required removing the water intake pipe O-ring (visible in lower left of picture) and removing two screws.

Waterpik WF-03 back removal 1

Waterpik WF-03 back removal 2

Once the back was removed, we are free to disassemble the central cylinder. It bottom was secured to the battery tray via four screws, and its top was held to the water intake and valve assembly with four more screws.

Waterpik WF-03 cylinder removal 1

Here’s another view of the disassembled parts, laid out roughly analogous to the way they were when assembled.

Waterpik WF-03 cylinder removal 2

Once we could see the motor gearbox assembly inside that cylinder, it was clear why this device stopped working: water has leaked past the diaphragm (black) and made its way to components below that point.

Waterpik WF-03 pump 1

If there were any lubrication on the gears, they have been washed away. And the motor’s external casing has corroded. It was not possible to move this mechanical assembly by hand, so we took it apart to see what has seized.

Waterpik WF-03 pump 2

When the motor was removed, it looked even worse than expected. Trying to turn its output shaft using fingers found it unwilling to move.

Waterpik WF-03 motor freed

But we were able to un-seize the shaft, possibly helped by an unintentional drop to the ground. Then after cleaning it up a bit and adding some oil to the bushings, it spins up again! Markings on this little motor proclaims itself to be genuine Mabuchi. Whether it is indeed the real thing or a knockoff manufacturer brazenly using the name I can’t tell, but any motor that can survive abuse, end up looking like this one, and still spin up again has my respect.

Waterpik WF-03 motor runs again

We reassembled the water pump core and it was pumping water again.

Waterpik WF-03 back up and running

We could pump water past the point where a Waterpik nozzle would mate with a rubber O-ring, but it started leaking out past that point as those sections weren’t designed to control water flow. I didn’t expect the pump to be so tightly integrated with the nozzle socket assembly and didn’t bring one of my spare Waterpik nozzles. But that was no barrier: we fashioned a substitute using a short length of pneumatic hose and parts from a ball point pen.


I wouldn’t use this for my dental home care anymore, but it’s certainly going to sit in my pile of interesting parts awaiting integration into a future project.

Tria Beauty Hair Removal Laser 4X Teardown

The best part of a local meetup is having different people bring in cool things that I would never have encountered in my own life. This week’s SGVTech meet is a prime example: I got to look inside an old hair removal laser. This is a product category I didn’t even know existed beforehand. Reading the product’s web site, it proclaims itself to be far more powerful than any of its competitors on the market, second only to medical grade equipment not sold to consumers. I don’t know if that is true, but power is certainly a theme. There are multiple safety hoops the consumer must jump through. A skin tone sensor in the base must verify the user’s skin color is within an acceptable range before it will even power on. And before the laser will fire, a secondary verification performed by a different sensor in the tip must pass.

The motivation for tonight’s teardown is the power subsystem. When plugged in for charging, the device gives all the indication of successful full charge, but it could never go through the first stage of its extensive power-up procedure. The manufacturer does not supply replacement batteries: while it’s possible the device is no longer safe to use beyond the life of the battery, it’s also easy to be more cynical about planned obsolescence. Tonight’s mission is to open it up and see if it can be brought back to life.

The exterior enclosure is an impressive work of industrial design, presenting a user-friendly appearance that hides the power and sophistication within. Popping a few plastic clips unveiled the device is dominated by equipment supporting a powerful laser. The battery module consumes majority of the interior volume, followed by a large heat sink and fan for thermal management.

Tria 4X laser components

The battery pack consists of two cells, and our first surprise was the 3.2V nominal volts listed on its label. This typically indicates lithium iron phosphate (LiFePO4) battery cells, which is known for high power delivery befitting a high powered handheld laser. However, these cells typically trade off power delivery with lower power capacity, but this pack claims 4.4 AHr which is far higher than any LiFePO4 cell I’ve seen. Tearing apart the outer plastic, we saw the pack is two cells wired in parallel, supported by measuring an open circuit voltage of 3.4. Two cells 2.2 AHr apiece is still very high by LiFePO4 standards.

We had a wide selection of battery cells we intended to try swapping in, from NiMH (visible in picture above) to standard 18650 cylindrical lithium batteries to lithium polymer packs intended for high amperage draw remote control vehicles. But before we start hooking up batteries, we should understand what power the device is looking for. So the battery pack’s wires were cut off and replaced with connectors to a bench power supply.

Tria 4X laser on power supply

We expected the device to power up with the power supply set to 3.2V, the nominal voltage listed on the battery pack, but there was no response. Turning it up to 3.4V was also unresponsive. Something inside this device is looking for a very specific power profile before it will activate. This may be one of the safety hoops, but it certainly dims our prospects of getting it up and running on other batteries.

Then a mistake was made: thinking the device might be running into the power supply’s current limit, a hand reached out to increase current but instead turned the knob to increase voltage far higher than 3.4V. A component on the circuit board started glowing and smoking, leaving behind a burnt hole so we can’t even read the part number anymore to figure out what it used to be.

Tria 4X fried chip

Oh well, so much for bringing the device back to life.

Now that it is well and truly dead, we have to abort the revitalization project and revert to our typical mode of disassembly for curiosity. The heat sink appeared to be a custom piece of machined metal, even the cooling fan might be custom due to how it clips in a way that conformed to shape of the heat sink. But obviously the star attraction is the laser assembly, and it didn’t look anything like what we expected. Behind the optical assembly we see… two pieces of golden colored metal?

Tria 4X laser with optics

Most of our collective experience are with LEDs in plastic packaging. If we use magnification, we can see a little bit of the semiconductor within but they don’t look anything like this. Our ignorance of solid state lasers meant we didn’t understand what we were looking at.

Tria 4X laser

Looking on the bright side, maybe it’s just as well we didn’t understand enough to play with it. This is a powerful piece of equipment, operating on wavelengths of light that we could not see. There is no blink reflex to save our eyesight in case of accident.

Burnt Speaker Teardown

There was a casualty of my laser+speaker Lissajous proof of concept: while exploring the limits of how far I could push a speaker, I went too far and burned one up. It was an unfortunate but expected part of playing with using components outside of their designed purposes. And now the dead speaker has one final role to play: as a dissection subject so we can see what’s inside. This is a irreversibly destructive process because speakers are not built to be disassembled and repaired. Once I plunged the blade into the speaker surround, I am committed.

Cut speaker surround

Once the surround was cut, I could access and cut the suspension underneath. After they were both cut I could lift the cone. Several problems were immediately visible. The voice coil that should have been attached to the bottom of the cone has separated, leaving a ring of charred material and a single thin strand of magnet wire. Emphasis on single: there should have been two wires for the coil! Also, lifting the cone released a strong odor of burnt insulation.

Speaker cone lifted

Since that thin strand of magnet wire is our only connection to the voice coil carcass still buried within its narrow slot, the only thing to do is to tug on it (gently) to unwind the coil. As wires were pulled, they occasionally brought up flakes of burnt speaker with them. Eventually, enough of the obstacles were removed that the charred remains of the voice coil could be recovered. It’s a pretty sorry sight and a fitting company to the smell.

Speaker voice coil recovered

I originally had the ambition of creating my own voice coil actuator out of the damaged chassis, by winding magnet wire around a 3D-printed replacement cone. But that’s before I saw how narrow the slot was. I could not make anything to fit in that slot, so the re-purposing plan was abandoned. We’ll just keep the big chunk of magnet because magnets are always fun. (Keep away from credit cards, though.)

The magnet assembly was held on to the speaker chassis by four big rivet-like structures. A drill press was summoned to remove the bulk of the metal. It was novel to see metal shavings align themselves to the magnetic field.

Speaker on drill press

After the majority of the rivet were removed, the chassis was placed in a vice and the magnet assembly was pried loose from the chassis.

Speaker magnet pried loose

This still left four protrusions to cut flush, and the tedious task of cleanup – the metal chips really wanted to stay with the magnet! But by the end of the night I have a hefty speaker magnet assembly.

Sony KP-53S35 Signal Board “A”

After this electronic vulture picked clean the power handling board “G”, attention turned to the other main circuit board at the bottom of a Sony KP-53S35 TV. There is a big letter “A” marked on the board, but I’m going to call it the signal board because this is where video signals enter the TV. In the lower-right corner are two entry point for RF. (One for UHF and one for VHF?) Adjacent to them are a few sets of RCA jacks for composite video + stereo audio. Finally, this TV’s premium video option in the form of a S-Video connector in addition to composite video and stereo audio.

Again there were component heat sinks that were very good at their job, making them difficult to unsolder with heat.

Signal board A heat sink before

So just as before, I turned to mechanical means, but a refined version: instead of ripping them out with brute force, I tried to drill out the attachment points.

Signal board A heat sink base

It is a challenge to make a drill bit stay on point while drilling into the conical profile of a solder joint, but it was easier once things got started. This approach is a trade-off: the brute-force way is fast and appropriate when I don’t care much about damaging parts. The drill method is slower but leaves components better preserved. In this specific case, I’d like to get it up and running again. More details on the next post.

Signal board A heat sink after

But it’s not all about removing big beefy heat sinks, this board also presented opportunity to practice delicacy. The power board was composed exclusively of through-hole parts, which is reasonable considering its job. In contrast, the signal board dealt with lower power levels and employed a few surface mount devices scattered here and there. This is an ideal test case to see if a paint-stripping heat gun can be used to remove surface mount devices (SMD).

Signal board A SMD before

Great news – it worked! And since SMD parts have far smaller surface area and less raw metal, it took only about 20-30 seconds of the heat gun on high before a pair of pliers were able to gently lift the part. I’m going to continue practicing this mechanical removal process for a while before I worry about function. So it is still unknown whether the chip has suffered heat damage.

Signal board A SMD after

The signal board had a lot of empty space, reserved for components that were never installed. Best guess: this circuit board supported multiple televisions and these components were to support features that were absent from this specific TV.

Signal board A blank area.jpg

At the end of the afternoon, the board is pretty bare and showing signs of heat stress. What pieces did I pull off this board? That’s the topic of the next post…



Sony KP-53S35 Power Board “G”

After high voltage transformer was freed, I looked over the rest of this board. Aside from a big “G” next to the Sony logo, I didn’t find a designation marked on it. I’m calling this the power board just because this is where the AC power cable came into the television. Power enters through a connector in the lower-left corner of this picture. Accordingly, most of the larger components are clustered near that area, implying power handling duties. Many also had thin sheets of metal attached, either as heat sink or as shielding or possibly both.

Power Board top before

Near the center of the board is a curious connector – it just has a wire that loops back into itself. What could be the purpose of such a thing?

Power board curious connector

A big beefy 20W resistor with very low resistance of 0.82 ohms hint at a shunt, possibly for measuring current flow.

Power board 20W resistor

Enough looking, time to pull off the interesting looking parts, meaning pretty much every component which is not a resistor or a capacitor. I first started with the ICs on the board as I wanted them to practice free-form circuit building. I doubt my first attempts will look good, so I might as well start by creating circuits around chips that are likely nonfunctional due to excessive heat used to remove them. I had the heat gun hot enough and close enough so solder melted in under 30 seconds. That heat can’t be good for the chip!

Power board ICs removed

Emboldened by success removing these little chips in short order, attention turned to the big convergence control modules STK392-110.

STK392-110 convergence control amplifiers

Sadly their big heat sinks were very good at their job of dissipating heat so I couldn’t reach melting point of solder holding them to the board. I turned to removal via mechanical means, which is a fancy way of saying “ripping that sucker out of there.” I first removed the screws fastening the heat sink to the chip, then started pulling and rocking the heat sink. The metal leg on the right side held strongly to the circuit board and broke the board. The other side, however, is different.

Power board mechanical removal

The left side of the heat sink seemed to have popped free of its leg which is soldered to board. It looks like a little drilling will be enough to intentionally separate the heat sink from its attachment bracket, and that worked to ease removal of the second heat sink.

Power board drill to separate

Once the heat sinks were removed, the heat gun could free the STK392-110 modules. I reunited chip and heatsink for whatever their future holds.

Then the heat gun were pointed at the rest of power-handling components. Transformers, rectifiers, etc. They are relatively durable components and are likely to have survived the heat of their removal if I ever dare to use them for a future project.

Power board misc parts

And here’s the aftermath: a heat-charred and distorted circuit board still home to many uninteresting resistors and capacitors. It will be dropped off at electronic recycle.

Power board back after