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

 

Sony KP-53S35 Power Amplifier Parts

A 21-year old Sony KP-53S35 TV we disassembled occupies a sweet spot for this curious electronics learner. It’s old enough that there are still discrete components we can look at, and new enough that information for those components can be found online. Here are two examples:

A Philips TDA6106Q is the most sophisticated looking component on the circuit board attached to the business end of the CRT. Datasheet says it is an amplifier, taking input voltage signal (0 to 8V) and amplifying it to a much higher voltage. (0 to 250V) It can handle signals almost up to 6 megahertz. The output pin of this chip can be traced to pin 8 of the tube. Best guess: this is how beam intensity is modulated to create a picture as the beam swept across the screen.

Philips TDA6106Q IC

Components with big heat sinks always draw attention – they tend to be the most powerful components on the board. Either because they are doing a lot of complicated work, or that they are handling a lot of power. The circuit board with the power supply and high voltage transformer also had a pair of these STK392-110 units. The fact there were only two was curious: almost everything in a rear projection television comes in threes, one for each tube, what purpose would a pair of something serve?

STK392-110 convergence control amplifiers

Looking up STK392-110 gave us the answer on both fronts: they are high power amplifiers used for the purpose of controlling color convergence. The high power (over 100W) explains the heat sinks, and convergence control explains why there’s only two of them. If we’re working to make sure all three colors converge at the same places on screen, we could leave one color alone and just adjust the other two.

This seems to be a commodity part used by many rear projection televisions, and their high power handling meant they do burn out. As a consequence there are replacement modules still available for purchase at very affordable prices. Unfortunately the market is large enough for there to be counterfeit items as well.

Gathering High Voltage Components of Sony KP-53S35

Now that we got a blurry dot on screen of picture tubes we removed from a Sony KP-53S35 rear projection television… it is encouraging for us to keep going and see how much further we can go. There are two main avenues of investigation: (1) How to make a better and tighter beam, and (2) how to control direction of that beam.

To help experiments on making a better and tighter beam, we’re going back to the harvested pile of parts. A control box with three knobs labeled “focus” seems promising. It also has three other knobs labeled “screen” whose purposes we’re not sure about. This box had been mounted with the knobs facing forward such that a technician can access these knobs while looking at the screen.

HV Subsystem 3 - focus and screen adjust front

The back side of this box has a few wires. Most significantly, a pair of wires went to each of three picture tubes. In this picture, we still see the wire pairs for the green and blue tubes attached. The empty spots are for the red tube, removed before this picture was taken. The yellow, brown, and upper left corner black wire is unknown. The red wire in the lower left is connected to the high voltage transformer.

HV Subsystem 2 - focus and screen adjust back.jpg

Pulling the camera back shows the system in a little more context.

HV Subsystem 1 - wires

Close-up pictures were then taken for each of the three picture tube PCBs for future reference.

Our earlier experiment used a transformer purchased off Amazon intended for something else – we had hoped its voltage would be close enough, and it was. Now for the best beam we want to get the correct voltage by using the original transformer which generated the voltages for these tubes. It lives on one of the two main circuit boards that had lived at the bottom of the television. This board is where the power cord connected, so it has the power supply and everything relating to high voltage. The transform is still attached to an unit that distributes voltage to the three picture tubes.

IMG_6963

The transformer isn’t expected to be terribly delicate, so the cheap hot air gun will be deployed. But before that, a picture of its PCB footprint was taken for possible future reference.

HV Subsystem 5 - transformer footprint

 

 

Cheap Seats At The Hot Air Gun Show

At a recent SGVTech meetup, newcomer Amir had lots to offer. One item that I picked up on was his assertion that a cheap Harbor Freight heat gun can be a low-cost alternative to fancy electronics hot air rework stations. I have one of those cheap hot air guns in my garage! Designed for home improvement projects like paint stripping, it is a big crude tool. I wouldn’t use it to assemble surface mount devices or anything I actually care about until I get a better idea of what I am doing. I’ll learn to handle it by disassembling parts that are either robust, or that I don’t care about.

The very next week, I got the chance to put that idea to the test when [Emily] and I felt inspired to try lighting up a CRT. The original driving electronics are no longer functional due to us crudely tearing them out of the TV, but the tube and a few associated accessories are still intact. To help us play with the tube, we thought it might be a good idea to remove a CRT socket to make it easier to access our tube’s pins. This is the ideal situation for testing the heat gun – a big socket should be robust enough to take the heat of a clumsily applied hot air gun much better than something delicate. This TV is also old enough to predate ROHS and lead-free solder, so we expect the solder to flow relatively easily.

I aimed the hot air gun at the solder joints at low setting. After a minute of inactivity, I turned it up to high. About a minute after that, we could see solder starting to melt. A few more seconds after that, all solder on the socket melted enough for us to remove it.

CRT socket removed from PCB

This was much faster and easier than individually undoing solder joints using a soldering iron and a solder removal tool. And the mission was successful: our newly freed socket made it easier to probe terminals and to make experimental connections with alligator clips.

CRT pin probing with socket

Xbox 360 Steering Wheel Teardown

I just bought the top-of-the-line Xbox One X in order to play Forza Horizon 4 in 4K HDR. I’ve also reclaimed my old Xbox 360 Halo 4 Edition, which I loaned out to a friend’s family but the children had lost interest in the older console. I got the console itself back, plus my old game library and all accessories. This all started when I went looking for my old Kinect sensor bar, but that’s a story for another time.

Physically, the biggest thing in this package was the Xbox 360 Steering Wheel. Built to offer realism through force-feedback and take severe physical punishment, it was big and beefy and takes up entirely too much space. A problem that almost certainly drove its retirement and replacement by a much smaller controller. Since it is not compatible with my new console, where I can play all four Forza Horizon games, I see no reason to keep it around in running condition.

Which means it is time for some fun!

I brought it to our weekly maker meetup where we can tear into this relic of the past. The big wheel is set aside for now.

Xbox 360 Steering Wheel 1 - wheel intact

We’ll start with the pedals. These are designed to sit on the floor and take the force of frantic game players stepping hard on them. They are made of extremely sturdy plastic with surprising heft.

Xbox 360 Steering Wheel 2 - pedal intact

It was straightforward to open up, where we can see it is fairly simple inside.

Xbox 360 Steering Wheel 3 - pedal open

All the force gets dissipated by heavy duty springs and metal brackets into the beefy plastic, leaving only the rotational motion to be read by simple position encoders which are likely just inexpensive potentiometers.

Xbox 360 Steering Wheel 4 - pedal electronics

That done, we start tearing into the wheel itself. Most of the visible screw holes are at the bottom, where it is curved to fit on our laps. Unlike the pedal unit, these screws are “security screws” with a post in the middle of the Torx shaped fastener. It proved to be a minor annoyance but easily overcome with brute force as we don’t care about putting it back together.

Xbox 360 Steering Wheel 5 - wheel lap mount

After the “lap desk” layer was removed, we repeat the process for the actual enclosure.

Xbox 360 Steering Wheel 6 - wheel enclosure

A lot of destroyed fasteners and plastic later, the innards of the steering wheel is visible. As expected, it is mostly empty space. To the left is a control board with three wire bundles leading to the rest of the wheel. There’s one controlling the motor to provide force feedback, one to a sensor to read steering wheel angle, and a wiring harness going through the center of the steering shaft to the wheel-mounted controls.

Xbox 360 Steering Wheel 7 - wheel innards

Here’s a closeup of the force feedback motor and gearbox. Mechanically, this area takes the brunt of forces players would apply to the steering wheel. So I expect I can reuse this robust assembly in a physically demanding project in the future.

Xbox 360 Steering Wheel 8 - ffb gearbox

However, it proved to be tricky to remove. The four obvious screws release the metal plate, but that is only part of the assembly. There had to have been fasteners coming in the opposite direction, but none were clearly visible. By process of elimination, we eventually figured out the screws were hidden under a stealthy sticker that matched its surrounding color and shape so well we didn’t realize it was a sticker.

Xbox 360 Steering Wheel 9 - cleverly hidden screws

After that discovery, it was trivial to remove the motor gearbox assembly.

Xbox 360 Steering Wheel 11 - ffb gearbox extracted

The main board was also removed for examination. The electronics people in the room looked over the board and noted the main processor has a Microsoft logo on it. We had expected to find name and designation for a microcontroller we might reprogram, but this is a custom chip.

Xbox 360 Steering Wheel 10 - mainboard

Teardown proceeded to the wheel unit itself, where we found another surprise: The big motor isn’t the only one providing tactile feedback. The bottom left and right corners of the steering wheel also housed vibration motors.

Xbox 360 Steering Wheel 12 - wheel vibration motors.jpg

The two motors appeared identical, but they had different sized weights affixed to their output shafts to produce different tactile sensations for users’ palms.

Xbox 360 Steering Wheel 13 - wheel vibration motors extracted

The shifter paddles in the back of the wheel also had to take some punishment, as people can pull on those pretty hard. Again, a lot of mechanical design dissipated any over exuberant energy into sturdy plastic pieces and metal springs, leaving just a simple mechanical motion to press on small push buttons on the back side of the wheel circuit board.

Xbox 360 Steering Wheel 14 - paddle shift buttons

Remainder of the in-wheel PCB was unremarkable with standard buttons.

Xbox 360 Steering Wheel 15 - wheel PCB

The physical wheel we hold in our hand, however, was interesting. Its weight led to speculation that it might have metal weights inside or possibly be formed from a steel tube. We put it through a metal-cutting bandsaw and found that it was solid heavy plastic all the way through. Three layers are visible: The crudely formed center (dark gray) which is likely just a C shape. Then a more precisely formed plastic layer was formed over it (lighter gray) which probably also formed the center of the wheel housing all the buttons and PCBs. Then finally, a soft rubbery rim was formed over that, with a dimpled texture for grip.

Xbox 360 Steering Wheel 16 - solid rimThis steering wheel controller was a lot of fun in its prime. It felt great in the hand making its best effort at realism. The robust construction took all manners of abuse (from children and grownups alike) without any sign of damage. This wheel was definitely not flimsy! I appreciated seeing all the work that went into making such a robust gaming peripheral.

Now all the potentially reusable parts like motors, springs, gearboxes, and electronics have been harvested and put away, consuming far less storage volume than the entire wheel and pedal assembly. The remaining (beefy) plastic is on their way to a landfill.

Fun With Tiny CRT

When we took apart the big old rear projection television, the same family also had an old VHS camcorder from the 1980s slated for disposal. [mle_makes] took it off their hands and merrily started taking it apart for fun components. First component to be brought to our weekly SGVHAK meetup was the viewfinder’s tiny CRT. I brought the box of Sony KP-53S35 salvaged RPTV parts on the same day so we could place the two picture tubes side by side with a ruler between them.

Tiny CRT 1 - Side by side with RPTV tube

While the big tube had 21 years of TV watching burned in to the surface, the little CRT looks to be in good shape. (Also, the RPTV tube was likely driven far harder to generate the necessary brightness.) And since the little tube was part of a battery-powered device (12 volt lead-acid!) the picture tube flickered to life with a DC power supply.

Viewed from the top, we are reminded how much of a space savings modern LCDs gave us. Both of these tubes are far longer than their picture’s diagonal size.

Tiny CRT 2 - Length comparison with RPTV tube

The little tube’s image was remarkably crisp and bright when viewed in person, a fact extremely difficult to capture in a photograph. The 525 scan lines of a NTSC signal meant this little tube was pushing 600 dpi of resolution!

Tiny CRT 3 - tape measure

All of these images on the tube were generated from an old video conference camera, which had a composite video output port that was wired to the tube’s control board. Here’s one of the test setups, using a scrap piece of paper and a simple smiley face drawn on it with a Sharpie marker.

Tiny CRT 4 - camera test setup

The best picture taken of the tube was when I narrowed the aperture to get a longer field of depth, so the camera is free to focus on something other than the actual picture and still get halfway decent results. (I think it is focused on the edges of the glass here.) An admirable amount of paper texture was conveyed on this tube.

Tiny CRT 5 - camera test image

A few weeks after this initial tiny CRT demo, it became the centerpiece of this Freeform Mini CRT Sculpture on instructables.com.

Sony KP-53S35 Teardown

SonyTD 01 - Final serviceThis Sony KP-53S35 rear projection television is over 21 years old and we’re going to pull it apart. The aim is to get parts for future projects that are difficult (or unreasonably expensive) to buy on their own. Plus a few auxiliary items because it’s easy to get them at the same time. The “shopping list” sorted by size are:

  • A large Fresnel lens that’s a core part of the main screen.
  • The large front-surface mirror reflecting picture onto screen.
  • Lens assemblies on picture tubes.
  • Speakers.
  • Caster wheels.

SonyTD 02 - Tag.jpg

Since this might get messy, the doomed TV was moved out to the driveway for dissection. The rear service panel is the obvious place to start. [mle_makes] has taken apart many RPTVs and was recruited as expert guide to the process. [amybaldwindev] has not taken many things apart before and is here to learn.

SonyTD 03 - Back panel

With the service panel removed, we can see the heart of the TV: picture tube and electronics driving them. The rest of a RPTV is basically empty space.

SonyTD 04 - Back panel removed

Next to be removed was the large rear mirror. I was a little disappointed to find this was an ordinary rear-surface mirror, not a front-surface mirror as I had hoped for. Still, it has many future project possibilities.

SonyTD 05 - Mirror removed

The largest two circuit boards were mounted on a tray that could slide out for servicing, giving us a better look at the heart of the machine. Aside from some beefy-looking heat sinks, there is little desire for whatever’s on these non-HDTV circuit boards. They’ll be stashed away and likely disposed in electronics waste disposal in the future.

SonyTD 06 - Tubes and electronics

Old age made the circuit boards uninteresting, but old age made the picture tubes novel. They were removed next, and their focusing lens assemblies removed.

SonyTD 07 - Tube lens removal

With the lens assemblies removed, we can see the picture tube behind a liquid cooling assembly. We knew to expect three tubes: one each for red, green, and blue. And it wasn’t too surprising to see color imparted by colored lenses. What’s puzzling is the fact the red and green tubes got colored lenses…. but the blue one did not. Do these tubes emit blue by default?

SonyTD 08 - Tube no lens front

The three tubes are different in other ways: The red and green tubes had an extra circuit board on their control yokes, but the two boards are clearly different. In contrast, the blue tube had no circuit board on its control yoke at all.

SonyTD 09 - Tube no lens rear

Here’s how the three tubes (and their control yokes) were mounted in the case, which may be useful if they are to ever light up again.

RPTV Picture tube and coil orientation

The coolant (most likely ethylene glycol) in the chamber in front of all three tubes were drained into a glass jar for safe disposal. (Or potential reuse.) Once drained, the cooling assembly was removed to expose the picture tube face. Visible on each face is a burned-in rectangle representing 21 years of TV watching. Due to the geometry of the optical path, the tubes on either side had a trapezoidal pattern (visible here) and the center tube has a rectangular pattern.

SonyTD 10 - Tube burn in

These large powerful high-voltage tubes are not going to be used for their designed purpose in the future, but the glass work is beautiful and I hope to find an aesthetic way to display them. All the components were stripped off the glass vessel.

SonyTD 11 - Bare tube

It’s a bit of a shame, as the wiring in the control yoke has aesthetics of their own.

SonyTD 12 - Control yoke

With all the components packed away, it was time to break down the cabinet. It is mostly built from injection-molded polystrene and should be recyclable.

SonyTD 13 - Plastic frame

This is where a reciprocating saw (the Harbor Freight knockoff of a Sawzall) became very handy.

SonyTD 14 - Breaking down

At the end of the day, a big bulky RPTV has disappeared. Its desirable components were packed for reuse, hazardous components were packed for safe disposal, and the remaining cabinet pieces broken up for household waste/recycling.

Yet to come: giving these salvaged parts new life.

Dell XPS M1330 Battery Pack Teardown

We had an earlier success tearing down a Dell laptop battery pack, where the six salvaged cells still have 70% of original capacity after ten years of service. However, that was from a laptop that could still boot and run from its battery pack. This XPS M1330 battery pack is in far worse shape. How much worse, we were about to find out.

The first critical detail was realizing the battery pack was not the original Dell battery pack. It is an aftermarket type of unknown manufacture. The earlier battery pack tear down yielded Samsung cells, we’re probably not going to get anything nearly as nice this time around.

Once the case was cracked open the suspicion was confirmed: These appear to be generic 18650-sized lithium cells with no manufacturer branding. The nine cells of the battery pack were divided into three modules in series, each module had three cells wired in parallel. The module in the worst shape exhibited severe corrosion and had no voltage across their terminals.

Corroded 18650

The other two modules were in slightly better shape, but they have self-discharged down to approximately 1 volt DC, well under the recommended voltage range. A web search found some details on what happens to overly discharged lithium cells. In short: the chemistry inside the cell starts dissolving itself. If recharged, the dissolved metals may reform in inconvenient ways. Trying to use these cells has three potential outcomes:

  1. Best case: The metals dissolved into the electrolyte will hamper chemical reaction, resulting in reduced capacity.
  2. Medium case: The dissolved metals will reform in a way that damages the cell, causing it to fail as an open-circuit. (As if no battery was present.)
  3. Worst case: The dissolved metals will reform in a way that damages the cell, but causing it to fail as a closed circuit. Short-circuiting the internals will release a lot of energy very quickly, resulting in high-pressure venting and/or fire.

The corroded cells that have discharged down to zero volts have the highest risk and will be discarded. The remaining cells will be slowly (and carefully) charged back up to gauge their behavior.

Dell XPS M1330 Power Port Salvaged Using Desoldering Tool

Recently a dead Dell XPS M1330 came across the workbench. The battery was dead and the machine fails to boot. After some effort at reviving the machine, it was declared hopeless and salvage operations began. Today’s effort focuses on the motherboard port for the AC power adapter.

Dell Octagonal PowerThe power plug on this Dell different from the typical Dell laptop AC adapter: octagonal in shape rather than round. The shape meant it could not be used on other Dell laptops designed for the round plug. However, the dimensions of the octagon are such that an AC power adapter with the typical round Dell plug fits and could be used to charge the laptop. So while the laptop could be charged with any existing Dell-compatible AC adapter, the AC adapter that came with this machine is specific to this Dell.

Once the XPS M1330 died, its octagonal plug power adapter is not useful for other Dell laptops. It still functions as a power supply transforming household AC to ~19V DC so it might be useful for future projects. To preserve this possibility, the octagonal power port will be recovered from the system board.

The solder used in Dell assembly was possibly one of the lead-free types and is definitely reluctant to melt and flow. Trying to desolder the power port using hand tools (desoldering wick and hand suction pump) had no luck. So this project was chosen as a practice run of using a dedicated desoldering tool, in this case a Hakko 808. The tip of this tool heats up to melt the solder, and with a press of the trigger an electric vacuum pump pulls the melted solder through center channel of the heated tip and into a chamber for later disposal.

The desoldering pump was able to remove more solder than hand tools could, but was still not quite enough to free the port. Using a soldering iron, some user-friendly leaded solder was worked back into the joints to mix with the remaining Dell factory solder. Upon second application of the electric desoldering tool, enough solder was removed to free the port from the system board with only minimal damage.

Desoldering Tool

A test with the voltage meter confirmed this port is now ready to be used to provide ~19V DC power to a future project.

Socket Extraction Success

 

Disassemble Smoke Detector

One of the smoke detectors in the house has started raising a lot of false alarms and was replaced after a 3:30AM episode. Naturally, we’re going to take it apart. Today’s home smoke detectors come in two types: ionization vs. photo-electric. This particular detector, a First Alert P1210, is a photo-electric detector.

The cover was held on by four screws, only one of which was immediately accessible. The remaining three were blocked by the paper label which was easily punctured for access with a screwdriver.

Smoke Detector Lidless

Inside the plastic housing is a surprisingly large circuit board, its battery, and piezoelectric alarm buzzer. A cursory examination of the circuit board revealed some pads for absent components, which likely meant this board is shared with higher-end models with more features. Beyond those empty pads, almost a third of the circuit board real estate serves no apparent purpose.

The brains of the operation is a single chip printed with the Microchip logo which made it easy to look up its datasheet. A search on its numbers identified it as a Microchip RE46C190 which is apparently a turnkey solution for anybody to build a smoke detector around the chip.

Smoke Detector Sensor and Baffle

The nose of the operation is an infrared LED paired with a detector, kept in a housing that keeps the detector out of direct line of sight to the LED. When smoke particles enter the detection chamber, it will be illuminated by the LED and reflect light into the detector.

There is no obvious indication of why this smoke detector started sounding false alarms. Perhaps some dust entered the detection chamber? A smoke detector chip shouldn’t sound the alarm for just any reflection, it should look for specific characteristics of smoke particles. But there’s a chance we are expecting too much of this little detector.

And even if it does panic at any reflection regardless of source, the knowledge is not particularly helpful. The detection chamber and the baffles surrounding it is not accessible for cleaning without taking the detector apart.

For the immediate future, these parts will sit in a plastic bag. Added to the stockpile of electronic parts for potential future projects.

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.

Old Cordless Drill

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 NEXTEC LED Work Light

Today’s project is to disassemble the NEXTEC LED work light and see if we can use it to adapt an old Black & Decker BHD9600CHV Dustbuster to lithium-ion power.

The wish list of the disassembly operation are:

  • Battery compartment: If we could use the battery compartment of the work light, don’t have to reverse engineer the dimensions of the battery pack and the slots needed to clip the battery in place.
  • Battery connector: If we could use the battery connector of the work light, we don’t have to reverse engineer the precise location and dimension of the metal contacts for drawing power from the battery.
  • Battery over-discharge protection: Unlike Ni-Cad batteries’ tolerance of discharge, over-discharging lithium-ion cells could cause permanent damage. As a result, most lithium-ion devices have a protection circuit and I’d like to pull that in.

The things we don’t care about:

  • LED array: There are plenty of LEDs of all color and brightness on every electronic tinkerer’s workbench. One fewer array would not be missed.
  • Switch: The work light’s switch is the type where a press closes the circuit, then another press opens the circuit. This is the right behavior for a light but not for a vacuum. Also: this switch was designed for a low-amperage LED and while it looks sufficiently beefy, it might not tolerate the amperage draw of a Dustbuster motor.

With these goals in mind we start with the obvious task of removing the four visible screws. After the screws were removed there was one more fastener: a small metal C-clip holding the two halves together near where the pinkie finger rests while holding the light. The clip was designed to require a specific tool for a clean removal. For people who are unconcerned about cosmetic damage, it could be persuaded to abandon its post with pliers.

Work Light Disassembled

Looking at the disassembled light, we see we can easily re-purpose the battery compartment and associated battery connector for the project. The third item on the wish list – the over-discharge protection circuit – is unfortunately incorporated onto the LED circuit board and not an easily separated part. We’ll just have to be careful when using the upgraded Dustbuster and not discharge it too much.

Having the battery compartment and electrical contacts is great. It bypasses a lot of iterative CAD work and 3D printing to pin down proper dimensions to fit the battery. The next step is to join the two devices together.

(Cross-posted to Hackaday.io)

No AC Adapter, No Problem! Alternate Power Source for an Acer Aspire Switch.

Once I was done gawking the clever magnetic attachment mechanism of the Acer SW5-012, it’s time to get back to trying to get it to run. The machine was able to power up on its remaining battery power for a little bit, but now it needs more juice. Since I was given this computer in nonfunctional “as-is” state, the AC power adapter was not part of the package.

Disinclined to spend any money on this machine, but willing to spend time, I went online to look for information about the AC adapter. Unfortunately there appeared to have been several similar but different computers sold under the “Acer Aspire Switch 10” name. And while it’s unclear if all of them use the same AC power adapter, the adapters were consistently stated to be an unit that outputs 12V DC.

This is great news as I have many ways to deliver 12V DC among my collection of tools and parts. But I have no plugs on hand that fits the existing power socket. I examined the power connector to the motherboard and saw four wires. A continuity check confirmed that it’s a simple positive terminal and ground terminal, with a pair of wires electrically connected for each. None of the wires are electrically distinct from power, so I don’t have to worry about data handshaking signals that are involved in charging certain other laptops.

Armed with this information, I removed the existing 12V power socket and the associated bracket. I cut the wire connecting the socket to the motherboard and soldered a JST RCY connector in its place.

Acer JST RCY adaptation

This type of connector is popular with remote-control aircraft and frequently used to carry roughly 12 volts (3-cell lithium rechargeable battery) at up to 3 amps. I reassembled the tablet, connected a 12V power source, and was reassured by illumination of the charging activity light. After a few hours, the tablet was charged up and ready to go again. Success!

 

Functional Simplicity of the “Acer Smart Hinge”

Yesterday’s post was about trying to bring an Acer SW5-012 back to life, which was fortunately as easy as reseating a ribbon cable. One of the reasons I was so eager to crack that thing open was my fascination with its hinge attachment mechanism. This was one of the “convertible” machines launched in the Windows 8 era and evolution of the category continued to this day with computers like the Microsoft Surface Book.

The hinge attachment/release mechanism for the Surface Book featured precisely machined components and electronics to control a wire of memory alloy. This Acer is a much cheaper machine so its nifty connector must also be simpler. Before I pried it open, I mentally tried to figure out how I would design such a mechanism.

At the time I thought the battery was flat, so I excluded any electronics in the design. It had to work without power, which made me think about magnets. A few small magnets to detect when the base is close to the screen, and pull against some spring-loaded arms to hold the thing together. When I pull on the screen, the force overcomes the springs to releases the arms.

Once I popped off the back cover of the computer, I could check my design against the answer and… well, I got the magnets part right even though it was based on a false premise (the battery was not flat like I thought.) And all the spring-loaded arms and clips and levers? Unnecessary complexity. I knew it had to be simpler than the Surface Book mechanism, but it was far simpler than what I imagined.

The actual mechanism consisted of magnets and… that’s it. Just some very cleverly placed magnets. When the screen is installed on the base, the magnets attract like we expect them to do, holding things together.

Acer Hinge Engaged

So what happens when we lift the screen away from the base? What’s causing that mechanical “click” sound?

When the base is lifted, the magnets in the screen is pulled away from the magnets in the base. Lacking the strong attraction, the magnets in the screen searched for the next best thing and finds a few metal plates slightly recessed into the cavity. The “click” is the magnet moving from the no-longer-there base magnet to the metal plate. When the magnets are attached to this inner metal plate, they are a few millimeters away from the edge of the unit but that’s far enough to keep it from picking up errant metal bits (paperclips, staples, etc.) while it is in tablet mode.

Acer Hinge Released

When the screen is reinstalled on the base, the screen magnet leave the metal plate in favor of the magnet in the base, making another “click”.

The Acer manual called it the “Acer Smart Hinge” and I agree it’s very smart – on the part of the people who designed it. Its simplicity lends to lower manufacturing cost and also to its reliability – no springs to break, no latch to wear out.

I am impressed.

Acer Aspire Disabled By Loose Cable.

I recently received an old Acer Aspire Switch 10 computer that no longer ran: there was no response when pushing the power button. The most obvious hypothesis is that the batteries are flat and need to be charged. Unfortunately, my gift of the computer did not include its matching AC power adapter.

If I was confident that was the only issue, I would go out and buy a power adapter. But I didn’t know if there were more serious problems in this machine and didn’t want to throw money at an unknown quantity. Besides, I received this computer on the premise that I wanted to take it apart for fun, so that’s exactly what I’m going to do.

Putting its serial number into Acer’s support site told me the model number (SW5-012) and part number (NT.L4TAA.018), but no service manual. I’m spoiled by Dell who usually releases a service manual detailing how to take apart and service a computer. Apparently Acer does not follow the practice.

There were no obvious external fasteners I could loosen, so I started prying at the visible seams to see if I could release plastic clips. Once I had three loose, the remainder (~25 in all) easily popped off in sequence.

My target was the battery module which I planned to remove and charge directly. Removing the battery required removing several pieces of tape. Some of these pieces of tape were applied over connectors, presumably to help the cables stay in place. One of these cables traversed the length of the battery so I had to remove the tape and the cable to free the battery. After I carefully peeled off the tape, I reached out to disconnect the cable and… it fell off freely.

Hmm, that wasn’t supposed to happen.

This cable connects the motherboard on one side of the machine to a small circuit board on the other side. The small circuit board hosts the Windows button, the volume up/down buttons, the headphone jack, and… the power button. If this cable was disconnected, it would explain why pushing the power button had no response.

Acer Power Ribbon

Since the battery was accessible now, I checked its voltage: 4.01V. Comfortably above the ~3.7V nominal voltage of a lithium-ion battery so the problem with this computer was not a dead battery. Maybe it’s the loose cable I just came across? I reinstalled the cable and pushed the power button again.

And… it’s alive!

Disassemble Monoprice Maker Ultimate (Wanhao Duplicator 6) Failed Relay

This is the main 24V relay on the control board of my Monoprice Maker Ultimate 3D printer, which is a rebadged and lightly modified variant of Wanhao Duplicator 6. An earlier blog post figured out why it died. (Short summary: the printer design drove this relay beyond its rated limit of 10A @ 24V.) Today let’s look closer at how it died.

There were clear visual indication of relay failure in the form of a heat-distorted casing with a hole melted into it.

Relay 10 - ClosedThere were no fasteners to release so the case had to be cut free from the base. Once the case was removed, we could see the guts of the relay.

Relay 20 - OpenLooking at the inside of the just-removed case, we can see a lot of heat damage. Black char marks the hottest areas, and discolored white marked the rest.

Relay 40 - Charred CaseIt’s a fairly straightforward relay, with the coil actuating an armature moving between contacts on either the plate above or below it. The armature+contact area is immediately behind the blacked charred bits of the case. And looking at the armature and contacts themselves, we see the relay died an unhappy death.

Relay 30 - Distorted ContactEverything in the contact area is distorted and/or charred. There is a black plastic-feeling piece holding everything in position relative to each other, and it could no longer do its job with heat distorting it and moved things out of alignment. Between the armature and the bottom contact is a blob of melted something that looks vaguely like solder. The bits of blue visible are parts of the blue casing that has melted onto this assembly. While the top contact looks OK in this picture, the side facing the armature is just as blackened and charred as the visible face of the bottom contact. The armature itself is barely visible here but it is actually discolored and distorted near the contacts.

From the Facebook user’s group, I’ve learned more recent revisions of the printer used a relay from the SRU product line to replace this SRD unit. I’m still trying to find a data sheet for the newer relay. I would hope that it is a drop-in replacement rated for at least 15A @ 24V, preferably 20A. And hopefully it would not die like this SRD-05VDC-SL-C relay did.

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.