Electric Blanket Control (Sunbeam PAC-215)

Electric blankets are an energy-efficiency way to stay warm during cold nights. If I’m going to stay in bed while sleeping, why heat the whole house? Heat just the bed and get a comfortable rest. But they don’t last forever, and this particular Queen-sized blanket stopped heating for unknown reasons. I’m going to take apart its two control units (one for each half of the bed) to see what’s inside.

According to the label, this is a Sunbeam PAC-215 STYLE 85KQP with a maximum power draw of 360 watts. I interpret PAC-215 to mean the functional designation and 85KQP to mean a specific cosmetic variation, but that’s just a guess. (And it doesn’t affect a teardown, anyway.)

Peeling back all the adhesive circles unveiled two Philips-head fasteners.

Once those two fasteners were removed, there were three plastic clips to undo before the bottom could be separated from the enclosure. We see many thick traces and wires of through-hole components. Four small Philips-head fasteners hold the circuit board in place, the larger fifth fastener is for the heat sink and can be left in place.

In addition to those four fasteners, the LCD is held by two plastic clips and blobs of hot glue.

Once removed, we could separate the circuit board from the enclosure. Curiously, I see a sheet of metal glued to enclosure top conducting from one of the four screws out to the front of the display area. It might be for grounding purposes, but there is no other metal for it to make contact. It’s not obvious to me what user scenario justified this effort.

I was amused to see that backlight for the LCD is just a pair of LEDs soldered to the board. Simple, straightforward, and functional. No fancy multi-layer light diffusers for this screen.

The circuit board has a white silkscreen marking of PEP003-0A.pcb on the left and a copper marking of FR4(94V-0) DD2 REVB on the right. This picture was rotated 180 degrees relative to earlier pictures to better read identifier on the large surface-mounted IC.


I can make out the ST logo but a search for “DD2ZW2” and “MP9ACO218E” on their site both came up empty. Based on the traces going directly to the LCD, this chip has LCD control capabilities. How much more? I don’t know. It might be a complete electric blanket controller solution for all I know. The other item with a ST logo is a BTB06 triac.

I then proceeded to disassemble the other controller, whose enclosure came apart the same way. I had expected to find two different circuit boards: a primary controller with majority of logic and a secondary unit purely for user interface purposes. I was wrong: the two circuit boards are identical. They only differ in how wires were soldered to each board. I followed their paths and drew a crude diagram.

The power plug enters the first unit and connected to points labeled “H” (Hot) and “N” (Neutral). These are forwarded to the second unit as H2 and BN, respectively. H2 enters the second unit at its own “H” and BN goes to the second unit’s “N”.

Outputs of the first unit are labeled BH and BS, which enters the second unit as BH3 and BS2, respectively, and forwarded on to exit points BH2 and BS. The second unit’s own output goes out as BH, and neutral is forwarded out to the blanket plug.

The blanket plug itself was interesting. It was made of injection-molded plastic and designed to allow loose tolerances due to the flexible nature of the plastic yet still offer lots of mechanical strain relief.

The story continues inside, with plenty of strain relief considerations. This should nearly eliminate any mechanical stress from acting on the four crimped electrical connectors.

This teardown was more interesting than I had expected, as the controllers were more sophisticated than I had given them credit for. That was fun in its own right. But the motivation for doing this teardown today (instead of later) was so I could get my hands on some simple bare LCD modules I could play with.

Melnor Garden Hose Watering Nozzle

As a change of pace from electronics teardowns: I’m taking apart something with no electronics at all: my very old garden hose watering nozzle. It’s been leaking for years, which is why I’ve had to turn the faucet off when this is unused. Otherwise, it wastes water dropping out from the front and the back. But recently it started failing in a new way: there is now a horizontal curtain of water when I pull its lever, spraying water everywhere from just behind the spray pattern adjustment knob. It is finally time for this guy to go, but not before I take a look inside.

A single Philps-head self-tapping plastic screw held the spray pattern selector knob in place.

With the selector knob removed, its seal and detent mechanism falls out easily. The white spring-loaded mechanism pushes into dimples in the selection dial for that satisfying “click” when we are lined up for a spray pattern. The rubber seal has lost its flexibility and became rigid with age. It could no longer seal against water pressure, causing this nozzle’s retirement.

Two more screws were visible and promptly removed, but this plastic piece did not release easily. I broke a bit of the lip (visible in upper-right area of the rim) trying to pull it out. No other fasteners or retention mechanism were visible.

If I could not pull it, perhaps I could push it? I started working on the back end. Unthreading the adjustment nut all the way allowed its removal.

Pushing on the thread, the front face popped free along with the piston assembly. A coat of rust clearly designated regions that had years of water exposure.

Inside the handle body.

Inside the front face.

Intact piston assembly.

I could only partially disassemble the piston assembly. In use the rear seal and its washer moves against the piston shaft and thus could be slid off the end. The spring followed easily.

However, the front seal and the X-shaped plastic guide keeping it centered in the cylinder never had to move and now it is held in place by rust. The plastic guide showing signs of abuse of my removal attempt. Even if replacement seals were available, I would not have been able to replace this particular wear item.

The lever hinge pin is riveted in place, requiring a drill to free it.

And finally, the soft handle surround was cut free of the metal core with a box-cutter knife. Doing this reminded me of that scene in Terminator 2 where the T-800 cut off living tissue covering its arm to expose the metal endoskeleton.

Taylor Food Thermometer

This Taylor food thermometer display went blank and stayed blank even when given fresh batteries, so it’s getting the teardown treatment before disposal. It appears to be a design that the company has made for many years with slight variations, here is a close cousin I found on Amazon. (*) I’ve found no mentions of repair instructions or replacement parts, this is a disposable device.

The first thing I wanted to check is construction of the temperature probe. There were two possibilities:

  1. The temperature probe is mostly metal, and the sensor is near where the wire is attached. This would be dependent on a metal with high heat conductivity to carry heat from the tip of the probe to the sensor at its base.
  2. The temperature probe is mostly hollow tube, and wires run the entire length of the probe to a sensor at the tip.

I started opening it up and got this far before slicing myself open on a sharp metal edge.

With a ritual blood sacrifice to the teardown gods, I decided to stop here. It is far enough for me to conclude that possibility #2 is correct and the probe is mostly hollow tube with the sensor at the tip.

Next I started prying against the shiny top surface of the device and found it was merely a cosmetic facade held on with glue and not hiding any fasteners underneath.

Four fasteners were visible behind the display so I started work there.

There is a piezo sound element embedded in the back, and a circuit board inside. Under that black blob is likely a chip that runs the whole show. What struck me are the areas to the left of the blob: there are a few round test points, but many more rectangular pads for components that aren’t there. Are they for calibration? Are they for adjustment? Are they to activate/deactivate features for other products in the lineup? Maybe a combination of all of them?

I see a single screw for the base. Removing that screw freed a small piece of plastic but did not free the entire base. However, it did let me see inside the base and distinct signs of additional fasteners.

Aha, I forgot to check for fasteners hidden under squishy feet.

With those screws removed, we can see the base has no active components. It has the battery enclosure, socket for the temperature probe, and a circuit board for all the switches and buttons to operate the device. All the components appear to be in good shape, I see no obvious signs of damage that might explain why the device stopped working.

The display is a custom LCD unit held on with the squishy conductive stuff I’ve seen before in tearing down electronics but didn’t know anything about. This time I went online and found this electronics StackExchange thread. Which linked to this one. Formally “Elastomeric connector” and less formally “zebra strips” (though a search with those terms also need to have “electronic” in the keyword list or else we’d get stuff about zebra the animal.)

I don’t plan on keeping the circuit board or any of the components on board, but I’ll hang on to the LCD for the moment. If I get around to probing the LCD in the future I’ll need to fabricate my own circuit board to make contact with the zebra strip. I can take this picture showing the connector pitch, but sadly I’ve already lost horizontal alignment reference and that’ll be a problem I have to tackle later.

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

Brother TZe Label Tape Cartridge Teardown (Don’t Put Secrets On Your Labels!)

While organizing my workshop, I labeled a lot of things with my label maker (Brother P-Touch PT-D400) and used up a cartridge. A common complaint with these TZe label tape cartridges is that they are really expensive. So now that I have an empty cartridge, I thought I would take it apart to see if I can see anything that justifies its expense. It turned out to be far more sophisticated than I had originally expected, but I still don’t know if I would call its cost “reasonable”. Plus I found an interesting security concern. Don’t use label makers for confidential information!

The only thing we can really see from the outside is a horizontal window designed to let us see how much tape is left. When full, there’s white visible behind the light blue area. That white spool’s diameter decreases as the tape is consumed, gradually running to what we see in this picture where very little white is visible behind the blue.

Looking around the perimeter, I see several little clips holding the lid to the body plus this white tag telling me what label tape is inside. I expect that I would have to cut this white tag along the seam, pop those little clips loose, and it should fall apart.

It did not.

Majority of holding force actually came from these posts that fit very tightly into their sockets, not the clips or the sticker. Dimension precision in injection-molded plastic is directly correlated to cost, so that’s where some of the money went: it’s pretty expensive to keep these posts and their corresponding sockets within the exact dimensions to fit and grip tightly.

After I opened up the cartridge, I see I had drastically underestimated the complexity inside. There are actually four spools, a few rollers, and many guides to keep three tapes of materials flowing properly.

Here are all the components of the cartridge. Multiple spools, and a few springs to maintain tension. I had expected a single spool of tape that gets spit out, so this is far more complex than I had anticipated. There are actually three spools of material: The white adhesive backing, the black ink (with take-up reel), and the clear laminate layer.

Here is a closeup of the clear laminate spool and the white adhesive backing spool. The clear laminate spool has black stripes in this picture because that’s how the cartridge signals the end. There were ~20cm left of this zebra stripe, not that I can think of much I could do with it.

Here is the other side, showing the adhesive backing still usable on what’s left of the white reel. It looks like remaining white backing can still function as double-sided tape if I wanted to put it to work.

The black ink tape was a surprise. It is a pair: a dispenser reel for fresh material and a takeup reel for used ink. What’s super interesting here is that the takeup reel has a clearly legible negative image of everything that has been printed. Unspooling the takeup reel a bit, we can clearly see that my most recent label was for a batch DC buck converters showing their adjustable voltage range and maximum of 5 amps capacity.

A valuable lesson from this teardown: avoid confidential information when using a label maker, because a motivated dumpster-diver can read that information off your discarded empty label tape cartridges.

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

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 board 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.

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.

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.

[Update 1: No future project. After it damaged other items with more rusty water, I threw them all away.]

[Update 2: I took apart another Waterpik.]

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.

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.

Disassemble Old Cordless Drill

While working on my NEXTEC Dustbuster project, I took the work-in-progress to various local maker meets to as a show-and-tell subject. This inspired another local tinkerer to bring a really old cordless drill for a compare-and-contrast session. It hasn’t run in years so nothing was risked by taking it apart. Which we did.

We see a motor that’s roughly in the same class as the motor in my Dustbuster. Instead of an air-moving fan directly attached to the motor output shaft, we have a simple reduction gearbox instead of the planetary gear popular with modern counterparts. Other missing convenience features common in current generation products include a torque-sensitive clutch and key-less chuck.

The most surprising part of this old design is how they implemented the two-speed mechanism. The trigger moves a switch into one of three positions corresponding to “off”, “low”, and “high” speed. Obviously “off” is an open-circuit and “high” speed connects all five (six?) battery cells to the motor. It’s the “low” that was a surprise – as far as we can determine, it connects three of the battery cells to the motor and bypasses the rest. This will certainly send less power into the motor, but it also results in uneven discharge pattern for the battery cells. Such behavior is considered absolute no-no with modern lithium-ion battery cells, and it couldn’t have been very healthy for these old NiCad cells, either.

In theory this drill could be revived with a battery transplant, or maybe upgrade to two-cell Lithium-Ion power. Whether it’ll happen depends on the owner, who should definitely find an alternative implementation for variable speed.

Disassemble Broken Garbage Disposal

A few weeks ago something under my kitchen sink started leaking water. I had hoped it was a simple plumbing failure that would be easy to fix. Perhaps a pipe has come loose or cracked a seal? Sadly this was not the case. Water was dripping off the bottom of the garbage disposal and its exterior was dry all around: Water was flowing through the interior of the garbage disposal which meant its useful service life has come to an end.

Before I dispose of the disposal, I wanted to cut it open to see exactly what failed. I guessed that a water seal has failed around the main motor shaft, and wanted to see if my guess was correct. But first, it was sent to sit in the garage and dry off.

Disposal 10 - StartLooking around the perimeter for fasteners, the four rods immediately stood out. They are spread around the perimeter, and almost the entire height of the disposal. I tried the easy thing first but they refused to budge with my flat-head screwdriver. So out came the angle grinder with the cutting wheel, which quickly cut the exposed shaft.

Disposal 15 - Severed rodUnfortunately that did not allow the top part to come free. Something else was holding it together. Whether it is a mechanism I don’t understand or corrosion I could not tell. But there were no other obvious fasteners to release on the top side, nor is there a convenient point to start prying.

So I started looking around the bottom end of the disposal, where there was a window cut into the bottom for wiring to enter the device. That allowed me to look inside to scout out where I could best use my cutting wheel to cut the bottom free.

Disposal 20 - Bottom openedOnce the bottom was cut free, I had a better view to find next best place to cut the stator free. When I pulled the stator off, I was very surprised to feel the rotor flex along with the stator because I had expected it to stay with the rest of the grinder.

Disposal 30 - PerforationThe source of the problem became clear once the stator came off: the metal plate separating the electrical motor from the grinder has been severely weakened by corrosion. I’m sure there were only a few (or maybe only one) hole when I pulled this from the sink, but the whole plate was corrosion weakened so it fell apart when I pulled the stator off the bottom.