Laser+Speaker Lissajous Proof of Concept

With LRWave 1.0 complete, I could focus on the mechanical bits of a Lissajous machine driven by that web app. The goal is to build a more accessible Lissajous machine that does not have the risk presented by high voltages involved in driving a CRT. It will not look as good as a CRT, but that’s the tradeoff:

  • High voltage electron beam in a CRT replaced by far lower voltage LED laser diode.
  • CRT deflection yokes replaced by audio speakers.

The proof of concept rig is driven by the same thrift store amplifier used in the successful CRT Lissajous curve demo. This time it will be driving speakers, which is what it was designed for, instead of CRT deflection yokes. The speakers came from the same source as that CRT: a Sony KP-53S35 rear projection television we took apart for parts so we could embark on projects like this.

Hypothesis: If we attach a mirror to a speaker, then point a laser beam at that mirror, the reflected beam will be displaced by the movement of that speaker. By using two speakers and adjusting beam path through them, we can direct a laser beam among two orthogonal axis X and Y via stereo audio waveform generated by LRWave.

For the initial test, mirrors were taped directly on speaker cones and arranged so laser beam is projected to the ceiling. This produced a satisfactory Lissajous curve. Then the mirror configuration were changed to test another hypothesis: instead of direct attachment to speaker cone, tape the mirror so it sits between the fixed speaker frame and the moving speaker cone. This was expected to provide greater beam deflection, which it did in the pictured test rig. However, the resulting Lissajous curves were distorted due to flex by the plastic mirrors and not-very-secure tape.

RPTV Speakers and masking tape

Experimenting with maximum deflection range, I pushed the speakers too far and burned one up. For a brief few seconds the laser beams were visible, reflected by the smoke of an overloaded speaker coil.

  1. I could see the laser beams, cool!
  2. Um… why am I able to see the laser beams?
  3. [sniff sniff]
  4. Oh no, the magic smoke is escaping!

The Lissajous curve collapsed into a flat line as one deflection axis stopped deflecting, and that ended experimentation for the day.

Sony KP-53S35 Signal Board “A” Components

Here are the prizes rewarded for an afternoon spent desoldering parts from a Sony KP-53S35’s signal board “A”.

Signal board A top before

The most visually striking component were the shiny metal boxes in the corner. This is where signal from the TV antenna enters into the system. RF F-Type connectors on the back panel is connected to these modules via their RCA type connector. Since this TV tuned in to analog TV broadcast signals that have long since been retired, I doubt these parts are good for any functional purpose anymore. But they are still shiny and likely to end up in a nonfunctional sculpture project.

Near these modules on the signal board was this circuit board “P”. It was the only module installed as a plug-in card, which caught our eye. Why would Sony design an easily removable module? There were two candidate explanations: (1) easy replacement because it was expected to fail frequently, or (2) easy replacement because it is something to be swapped out. Since the module worked flawlessly for 21 years, it’s probably the latter. A web search for the two main ICs on board found that the Philips TDA8315T is a NTSC decoder, which confirmed hypothesis #2: this “P” board is designed to be easily swapped for a TV to support other broadcast standards.

The RCA jacks are simple and quite likely to find use in another project.

Miscellaneous ICs and other modules were removed mostly as practice. I may look up their identifiers to see if anything is useful, but some of the parts (like the chips with Sony logo on top) are going to be proprietary and not expected to be worth the effort to figure out what they do.

The largest surface mount chip – which I used as hot air SMD removal practice – was labeled BH3856FS and is an audio processing chip handling volume and tone control. Looking at the flip side of the circuit board, we can see it has a large supporting cast of components clustered near it. It might be fun to see if I can power it up for a simple “Hello World” circuit, but returning it to full operation is dependent on the next item:

What’s far more interesting is nearby: the TDA7262 is a stereo audio amplifier with 20W per channel. This might be powerful enough to drive deflection coils to create Lissajous curves. The possibility was enough to make me spent the time and effort to remove its heat sinks gently and also recover all nearby components that might support it. I think it would be a lot of fun to get this guy back up and running in a CRT Lissajous curve project. Either with or without its former partner, the BH3856FS audio chip above.

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.

Lissajous Curve Is An Ideal CRT Learning Project

Lissajous curve with shorter exposure

It was satisfying to see our CRT test rig showing Lissajous curves. [Emily] and I both contributed components for this cobbled-together contraption, drawing from our respective bins of parts. While the curves have their own beauty, there were also good technical reasons why it makes such a great learning project for working with salvaged cathode ray tubes. Mainly for things we don’t have to do:

Focus: We weren’t able to focus our beam in our first work session. We couldn’t count on sharp focus so we appreciate that Lissajous curves still look good when blurry. Thankfully, we did manage better focus for better pictures, but it was not required.

Modulation: To create a raster image, we must have control over beam brightness as we scan the screen. Even if doing arcade vector graphics, we need to be able to turn the beam off when moving from one shape to another. In contrast Lissajous curves are happy with an always-on dot of constant brightness.

Deflection: To create a raster image, we’d need a high level of control over the tube’s deflection coils. We’d need to create a constant horizontal sweep across the screen, as well as scanning vertically. HSYNC, VSYNC, all that good stuff. In contrast driving deflection coils for Lissajous curves require far gentler and smoother coil changes.

Geometry: Unlike modern flat panel displays, CRT can have geometry distortions: pincushion, trapezoidal, tilt, they’re all annoying to adjust and correct in order to deliver a good raster image. Fortunately, a Lissajous curve suffering from geometry distortions still look pretty good and allow us to ignore the issue for the time being.

There is a long way to go before we know enough to drive these tubes at their maximum potential. For one thing, it is running at a tiny fraction of its maximum brightness level. The tube’s previous life in a rear projection television was a hard one, visible in the above picture as a burned-in trapezoid on its phosphor layer. Driven hard enough to require liquid cooling, it would be so bright to be painful to look at and that’s when the beam is scanning across the entire screen. A Lissajous curve covers only a small fraction of that screen area. Concentrating a full-power beam in such a small area would raise concerns of phosphor damage. As pretty as Lissajous curves are, I don’t want them permanently burned into the phosphor. But we don’t have to worry about it until we get beam power figured out.

CRT Test Rig Produced Lissajous Curves

Last night’s CRT exploration adventures with [Emily] produced beautiful Lissajous curves on-screen that looked great to the eye but were a challenge to capture. (Cameras in general have a hard time getting proper focus and exposure for CRT phosphors.) Here’s a picture taken with exposure time of 1/200th of a second, showing phosphor brightness decay in a simple curve.

Lissajous curve with shorter exposure

Due to this brightness decay, more complex curves required a longer exposure time to capture. This picture was taken with a 1/50th second exposure but only captured about half of the curve.

Lissajous curve with longer exposure

Our test setup was a jury-rigged nest of wires. Not at all portable and definitely unsafe for public consumption. It required a space where everyone present are mature adults who understand high voltage parts are no joke and stay clear. (And more pragmatically, if an accident should occur, there will be other people present to call for immediate medical attention.)

CRT Test Rig angled view

Our beam power section consisted of two subsystems. The first is a battery that supplies low power (8 volts and less than 1 watt) to heat the filament. Using a battery keeps it electrically isolated from everything else. The second subsystem supplies high voltage to drive the CRT, and we keep a respectful distance from these parts when powered on.

CRT Test Rig beam power system

Connected to the tail end of the tube is the connector we freed from its original circuit board, wired with a simplified version of what was on that board. Several pins were connected to ground, some directly and others via resistors. The two wires disappearing off the top of the picture are for the heated filament. Two wires for experimentation are brought out and unconnected in this picture. The red connects to “screen grid” (which we don’t understand yet) and the black connected to an IC which we also don’t understand yet.

This is a rough exploratory circuit with known flaws. Not just the two wires that we haven’t yet connected to anything, but also the fact when we connected its ground to transformer’s ground, the tube flared bright for a fraction of a second before going dark. We only got a dot when connecting transformer ground to the filament heater negative, which was unexpected and really just tells us we still have a lot to learn. On the upside, something in this circuit allowed our “focus” wire to do its job this time, unlike our previous session.

CRT Test Rig tube wiring

But that’s to be figured out later. Tonight’s entertainment is our beam control section, which sits safely away from the high voltage bits and we can play with these while our tube is running.

CRT Test Rig beam control system

Controlling vertical deflection is an old Tektronix function generator. This is a proper piece of laboratory equipment producing precise and consistent signals. However, its maximum voltage output of 20V is not enough to give us full vertical deflection. And since we only had one, we needed something else to control horizontal deflection.

That “something else” was a hack. The big black box is a “300W” stereo amplifier, procured from the local thrift store for $15. Designed to drive speaker coils, tonight it is driving a CRT control yoke’s horizontal deflection coil instead. It was more than up to the task of providing full deflection. In fact, we had to turn the volume down to almost minimum for tonight’s experiments. A cell phone running simple tone generator app provided input signal. Not being a precision laboratory instrument, the signal generated was occasionally jittery. But enough for us to have fun producing Lissajous curves!

 

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

Old TV Picture Tubes Lights Again

When we tore apart an old rear projection television a few weeks ago, I did not expect those picture tubes would ever light up again. We took everything apart quickly within the narrow time window, so we didn’t have time to be careful to keep the electronics driving those CRTs intact. Those electronics are in pieces now, and in that writeup, I said the tubes were beautiful glass work and I hoped to display them as such in the future.

Well, there has been a change in plans.

On the same day as that teardown, [Emily] was gifted an old non-functioning camcorder. She has since taken that apart, too. The first component to see reuse was its tiny black and white viewfinder CRT. And as she dug deeper into the world of old CRTs, [Emily] came across this YouTube video by [Keystone Science] going over the basics of a cathode-ray tube and shared it with me. We were inspired to try lighting these tubes up again (without their original electronics) at yesterday’s SGVTech meetup.

The first step was to straighten out the pins at the rear end of our salvaged CRTs – they got a bit banged up in transport. A quick web search failed to find details on how to drive these tubes but probing with a meter gave us a few candidates for exploration.

Probing CRT pins

  • A pair of wires had around 8 ohms of resistance, highest of all wire pairs that gave a reading. This is likely the heating filament.
  • A few other wire pairs gave readings we didn’t understand, but several of them had some relation to a common pin. The common pin was thus our best candidate for cathode pin.

We knew the anode is connected to the side of the CRT, so now we have all the basics necessary to put a blurry dot on screen. A bench power supply was connected to the eight ohm load, and a few seconds later we can see a dull glow. Then a high voltage transformer was powered up across our anode and candidate cathode.

RPTV picture tube and transformer

After a bit of debugging, we have our blurry green dot! We proceeded to power up the other two tubes, which gave us a blue dot and a red dot. The colors look good to us, but apparently they’re not quite the right colors because during our TV disassembly we saw some color filters on the red and green tubes. (The blue tube had no color filter.)

During the course of the evening, the quality of our dot varied. Most of the time it was a blur approximately 5mm in diameter. On one occasion it bloomed out to 3cm diameter and we didn’t know what had caused it. Likewise, we had a pinpoint bright dot for a few seconds not correlating to any activity we could recall. As far as driving a CRT, we know enough to be respectful of the high voltage involved, but obviously we still have a lot more to learn. It’s just as well we don’t know how to focus the dot, because in the absence of sweep, a constant bright focused dot would likely burn a hole in the center of the screen’s phosphor layer.

A first step towards moving the beam was to put some power on the magnetic deflection yokes. These coils of wire were hooked up to a function generator, and we were able to get movement along one axis. Its maximum output of +/- 20V could only deflect a small fraction of the screen size, but it was something.

We didn’t have a second function generator on hand, but we got movement along another axis using magnets. They were taped to a shaft that was then put into a cordless drill. Holding the spinning drill near the control yoke induced movement along the other axis. Combined with the function generator, it allowed us to make a few curves on screen.

RPTV Red curves

Tinkering projects with visual results are always rewarding. With this success, there might yet be life ahead for these tubes as something other than pretty glass. A search found a hobbyist’s project to drive a CRT for an XY vector arcade monitor. That project page also linked to an excellent description of vector CRTs as used in old Atari arcade machines. Lots to learn!

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.