Rear Projection TV Teardown
Today we are tearing down a rear projection TV to see what kind of components we can salvage, and to determine whether recycling these appliances yourself is a viable option.
The victim today is a 120cm Samsung rear-projection TV that had definitely seen better days. I spied it dumped on a vacant block and some friends kindly retrieved it for me with a great deal of effort.
It has some cracks in the screen and is missing some parts and panels from the sides.
I am not sure exactly what has been removed, but there are numerous wires that must have been connected to something.
On first impressions this TV does not appear to have been in the weather for long.
CRT tubes can retain power after the TV has been unplugged. None of the old TVs and monitors I have dismantled in these articles have retained power, but I always discharge them anyway.
Tearing It Down
Other than the plastic rear cover, this unit is made from timber and held together by self tapping screws with 6.4mm bolt heads. This is a refreshing change from the usual plastic cases we tear down. Most of the waste from this project can hopefully be reused for extra shelving in the cave. The timber is a mixture of MDF and traditional chip board.
After removing the rear cover the next thing we detached was a large mirror that acts as a reflector for the projectors. This was a good score for starters, It is a nice mirror cut to an interesting shape and mounted on a black MDF board. This I will certainly use somewhere.
With the mirror gone we could now see "the guns". These formidable looking optical lenses sit atop three CRT projectors.
These look like giant robot eyes and they must be good for something. More on that later in the article.
We then removed the rear cover from the lower half of the unit
There is a lot of wiring in there, and you know you can never have too much wiring. There are also many separate PCB boards, some with multiple heat-sinks. It is dusty, but that allows me to see that there has been no actual water inside the unit.
We removed all the cables we could, then cut any others. Then we removed the projector assembly.
This is an impressive looking piece of kit. It consists of three CRT tubes like the ones found in traditional TVs. They are much smaller, but each has its own neck-board and deflector cone just like TV tubes.
I am curious about the square box in the image above. It has two input wires and six output wires with a turnpot allocated to each.
The tubes are each a different colour, red, green and blue. They are directed through three lenses, which focus the individual beams into an image on the screen.
There are ten individual circuit boards inside this unit.
The main board is packed with heat-sinks and large capacitors and resistors up to 10W.
It also harbours the high-voltage transformers, or flybacks, that fire the CRT projectors.
The next board (pictured below) has fewer components.
Of interest to me is the EPROM chip in the bottom right corner. This chip is reprogrammable and could be useful, but I think I have enough to learn with my current projects without learning how to work with these at the moment.
There are some zener diodes and a selection of header plugs that match the flat cables we removed earlier. Most of the other IC chips on here seem to be specifically related to televisions.
Board three seems mainly audio-visual related. It also has some zener diodes and capacitors, along with half a dozen small three-legged transistors.
Board four has a few crystal oscillators and some resistors, diodes and caps, but it also features an assembly with a collection of turnpots. This board lacks the traditional labelling format for its components such as "C" for capacitor, "R" for resistor, etc, so I don't know if these turnpots are standard variable resistors or something else.
The bright-green resistor-like objects pictured above and below are actually inductors. Just talking about inductors makes your head hurt, so we'll discuss them no further.
Board five has a scattering of the usual suspects but attached to the heat-sink are a pair of LM780x voltage regulators. I'll discuss these little beauties later in the article.
Board six has more oscillators and zener diodes.
Board seven is the audio amp. Some people may have a use for this board in its existing form but I don't really play with much audio stuff so I will raid it for parts.
I believe board eight is the other part of the audio amplifier. It has MOSFETS attached to the heat-sink and a variety of caps, diodes and resistors. There are also eight small transistors scattered about.
Board nine houses the main power switch for the TV.
Board ten has the IR sensor and some LEDs.
Boards 11, 12, and 13 are the CRT neck boards. They each house a MOSFET with heat-sink, as well as capacitors, diodes and big ceramic resistors.
Board 14 is a mystery. Other than the speaker connectors and a plug, there is nothing on this board. They must have had some left over from another product and decided to reuse them like this.
That is quiet a collection of circuit boards. It took my cave assistant about ten minutes to de-solder the components in the image above. There are twice as many parts remaining on the boards.
Other useful parts
As with anything containing CRT tubes, there are deflector cones.
These contain pure copper.
There would be over half a kilo of the precious metal here. Don't expect to get rich from one TV, but if you teardown enough TVs and monitors you could make some money from the copper.
The screen consists of two pieces, an opaque layer inside called a fresnal lense, and a clear layer outside that may be of some use.
As Grant, Max and Ja have pointed out in the comments, fresnal lenses are pretty cool, especially if you want to set things on fire using the sun. I found an interesting article on fresnel lenses here.
These cables are useful for projects if you can salvage the header plugs they connect to. These headers are difficult to remove from most circuitry, but TV boards generally seem to be human-soldered, meaning you can remove components quite easily.
The cables also feature single core wires so you can use them with breadboards.
As I mentioned earlier, most of the case for this TV are made from MDF and chipboard.
These materials are perfect for shelving and many other applications.
The sides of the case are MDF.
The rear panel is the only substantial part made from plastic and I can't help thinking this could be usefull for some purpose in its current form.
Nearly all of my projects require some form of voltage or current regulation, so I am always on the look out for power regulation chips.
I salvaged four 780x CT chips from this TV.
I have been using LM317 chips for power regulation to this point and they work incredibly well. See how to build an adjustable power supply for just a few dollars to find out more about the LM317 regulators.
The 780x CT regulators from this TV are similar but different to the LM317s. Rather than adjustable voltage they provide a set voltage equal to the last two numbers in the name. They are supposed to limit current output to 1.5 Amps.
In the image above, the green chip is a 7805CT for 5v output, the blue chips are 7808CTs at 8v and the red one is the 7812CT at 12v.
I have briefly tested these regulators and they do provide an accurate voltage but when I tried to check current the chip allowed almost 2.5 Amps to pass through and became hot to touch very quickly. The LM317s I am using, on the other hand, strictly limit current to the level you choose.
I will keep toying with these and write a tutorial for their use when I work them out.
I am yet to use any MOSFETS in my projects but I am about to start. MOSFETs are a type of switching transistor that allow you to control large voltages using smaller, signal-strength voltages from a microcontroller.
I salvage many motors from printers, etc, and I currently use cheap H-bridge type motor controllers to run these. I believe I can build my own controllers for these motors using MOSFETs.
There are at least a dozen of these MOSFETs in one of these TVs. There are also plenty of heat-sinks to cool them.
Resistors and capacitors
Resistors, diodes and capacitors are cheap to buy, but there is an environmental cost in their production. I have salvaged enough of them from this teardown to complete many projects.
I suspect some of the massive capacitors would actually cost more than spare change, so there are real money savings available here.
I look forward to playing with the lenses from the CRT projectors.
From the research involved in writing this article I know these assembles consist of a main lens and another called a C-element, a convex lens. I will write an article on these assemblies when I have had time to tinker with them further.
The mirror was a real bonus. I have not decided where to put it yet, for the moment it looks okay on my desk.
Now, the real question. Is it viable to recycle a rear-projection TV at home?
Firstly, the cons
They are bulky and very heavy. My friends collected this one on the back of a ute, but there is no way you would fit it in a normal car. They require at least two strong people to lug them around.
Although most of the exterior of this unit is made from reusable timber, you will still be left with a substantial amount of waste after you strip the electronic components, specifically the bare circuit boards and three CRT tubes.
Tearing down just one of these units will provide you with enough resistors, capacitors, diodes and MOSFETs to create many new projects. You will also have all the heat-sinks you could need. There are switches, turnpots and tons of cables and wiring, as well as speakers and half a kilo of pure copper. And don't forget the voltage regulators. You never know when you may need them.
So, to answer the question. If you already have one taking up space somewhere then it would surely be worth taking it apart and claiming some parts before you dispose of the unit. If not, it is up to you to decide whether to actually bring one of these home to salvage.
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