80cm Broken LED TV Turned Into 50W Remote Controlled Light Box

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Introduction: 80cm Broken LED TV Turned Into 50W Remote Controlled Light Box

About: I'm an electronic and software engineer

Today we will transform a broken 80cm LCD TV into a remote controlled light box for light therapy.

I brought the TV for cheap money as the LCD was broken. The TV used LED technology for the back light and everything worked fine. It's form a Chines brand "HARROW", nothing special.


Step 1: Open the TV

The first step: open the thing: very simple, unscrew the screws ...
That is how it looks like inside.

Step 2: Remove the LCD Panel

Now we need to remove the LCD panel and only keep the back light system.

To do this we need to disconnect the LCD panel from the main board and unscrew the screw that hold the LCD in place (the metal bars on the sides). Now we can see the back light system, which is basically just a white surface.

Step 3: Hack the Brigthness Control System

When you use you're TV as usual you can control the brightness with the remote control. As we don't have access to the configuration screen any more (as we don't see it ...) if we want to use the full power of the back light we need to hack the control system.

To do that I first checked the datasheet of the panel. My panel is a LG LC320DXN. You can find the data sheet easily on duckduckgo or google.

Going to the back light module specification shows us that the back light power is controlled by a PWM pin on the inverter board. There is also a pin to enable/disable the entire panel.

If we always want the maximum power out of the LEDs we simply need to put always a high logic level on the PWM pin. So I simply cut the PWM cable and soldered it on the enable/disable pin. If the panel is on the enable/disable pin will have a logic level high (5.0V) and so the PWM will be at maximum.

On the board, the pink wire is the PWM wire, just cut it and solder it on the enable/disable pin, here the gray one.

Step 4: Result!

Now what do we have? A remote controlled light source!! Yes, it you power up everything again, the TV will light up as usual if you use the remote control. Of course the TV does not know the LCD is not connected any more!

As we hacked the brightness system the light power will be at maximum all the time.

50W of LED is quite powerful!

Step 5: Bonus 1: Take a Deeper Look Inside

Just to see how it is made inside I took a deeper look inside. If you remove the black platic holding the back light system together you will be able to see 4 optical layers. (on my photo there are only 3, I removed the upper one because it's kind of a polarizing filler only useful for the LCD panel). The last layer is a 3 mm white platic pane and
the 2 upper ones are translucent paper to make the light as uniform as possible.

If you remove them you will finally see the LEDs.

Step 6: Bonus 2: Remove the Remote Control to Use a Wall Interrupter

Okey, this is pretty cool but useless when you want to use the wall interrupter as with usual lights. So lets take a look at the back of the screen: There are 2 boards: the green one for the logic and the beige one is the power supply. We need to get rid of the green one and to do that we need find the different enable pins on the power connector between the two board.

This is quite complicated and I would not recommend you to do this if you’re not sure about what you’re doing. Keep in mind that there are life dangerous voltages in game. I checked the different cables with a multi-meter and found out 4 cables:

-one delivering a 3.0V – 4.0V unstable voltage when the power supply is on standby and 5.0V if the power supply is enabled

-one that if connected to 3.3V enables the power supply

-one that if connected to 3.3V enables the back light

If we connect them together we have:

-the power supply enabled

-the back light enabled

and finally it works as a usual light: put 220V on the power supply and it will light up!

1 Person Made This Project!

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19 Comments

0
OlgunG
OlgunG

Question 5 months ago on Step 6

Hello!
y monitor has backlight leds. I have an mp3394 controlling this. I want to control these backlight leds with a switch. How can I do? I drew the mp3394 link of the monitor scheme in the image file.

20210121_135922.jpg
0
fefc
fefc

Answer 4 months ago

Hi,
according to what I have found about MP3394, you would need to put 5V on the green wire to enable the leds. The +5V you indicated top left is probably not enough, with 12 Leds 24-28V should do. It's best to check the original supply (16V Capacity would mean max voltage is about 12V). White wire is probably a PWM signal which allows dimming. Setting to ground should set leds off, setting to 5V should set leds to full power.

Then, depending with what you want to switch: put the switch on the 220V part, so you either enable the whole thing or nothing. If you need something else you could put a switch on the green wire. Leave it disconnected would shut the led off. Setting it yo 5V would enable the leds.

Hope that helps,
best

MP3394_385_1_1.jpeg
0
OlgunG
OlgunG

Reply 4 months ago

About 33 volts are supplied from the power board of my monitor to the backlight LEDs.
The images and circuit diagram of my monitor are very similar to the images here.

BENQ-GL2450-B-4H-1KV02-A51_slika_O_109389247.jpgBENQ-GL2450-B-4H-1KV02-A51_Üstten görünüm.jpg
0
fefc
fefc

Reply 4 months ago

Kind of difficult to help you here, your easiest option would be to buy a led driver, so you don't have to deal with the old electronics. Take a look here, that was another project where I removed the electronics https://www.instructables.com/Turn-a-broken-22-dis...

Many years ago so won't be able to help much anymore, sorry

0
OlgunG
OlgunG

Reply 4 months ago

Hi,
The + 5V you specified in the top left is probably not enough. You warned me. But +5 volts is not my choice. It is in the monitor's original circuit. I wanted to draw the diagram and show it to you. I hope I could explain it to you.
I apologize for his inaccurate phrases. There are mistakes for him in using Google translate.

0
OlgunG
OlgunG

Reply 4 months ago

Hello, I am sending you the measurement results I made at the Cn701 connector on the monitor's power board. Please see.

20210115_150157.jpg20210119_122613.jpg
0
michaelgibson1315
michaelgibson1315

1 year ago

Do you have any more pics of the last steps? Or of all the steps for that matter. Having trouble finding a 5 v supply on my board.

0
fefc
fefc

Reply 1 year ago

Hi, sorry I've done this project a few years ago so won't have any more pictures. Do you have a multi-meter? This might be your best chance, otherwise sometimes on the board it might be written...


0
jiri.svoboda.2002
jiri.svoboda.2002

2 years ago on Step 6

I;ve done it. I've removed all boards but Power and Led driver.

To make it working, in Power board I had to connect to 5V

- Power_ON

- PWM (max brightness)

-BL_ON(enables led driver)

0
michaelgibson1315
michaelgibson1315

Reply 1 year ago

Do you have any pics or vids. Ive hit a roadblock with standby shutting it off after a couple min. And would love to crank the brigjtness

0
WilliamA179
WilliamA179

Question 3 years ago on Step 6

I don't know if you will get this, but your article is about the Best and easiest one I've found(hundreds of searches over smooth of research) I'm broke as hell and I'm trying to learn all I can about electronics. I came up on a 32 inch smart LCD, and broke the scree and pretty bad, I'm doing the same thing with back light. But that leaves Roku chip and smart programs, can I do anything with this? Like external Roku or install in older TV? If you need more specs I can pull out any part

0
SaraM195
SaraM195

3 years ago

Anyway you could help me? I cant find a datasheet nor do i honestly know what im doing i can give you my email address

0
cherry.miller25
cherry.miller25

4 years ago

Hi ...

Its a really impressive work...

Can you me help in understanding the power supply specifications for the led backlight from my broken tv "Vizio E320-A1"

I searched in duckduckgo (or google) but its not very clear to me.

I want to use these led lights to make a softbox.

I would really appreciate your help ....

0
hubi
hubi

5 years ago

I sould have read this before. I made a lightpanel out of another LED TV. Mine has 5 of the same LED strips that you have in yours. Each consisting of 9 LEDs in series, the stripes are also in series, i measured it was powered by 146V 330mA. When I turned it on via TV remote it went off (standby) after a short time cause there was no signal. So I built my own supply. I power the strips in parallel with a old 19V laptop supply and an boost converter set to 30V the strips are now in parallel, each strip has a 2.7 Ohm resistor in series, the current per string is only 150mA that is bright enough to me, with 330mA per string it does not get much brighter. I use this lightpanel as therapeutic light against the winter blues. My Screen is from a tv that fell down so the LCD was broken.

0
fefc
fefc

Reply 5 years ago

You could also take a look at constant current (C.C.) power supplies. Some years ago they where expensive but nowadays the price is acceptable. I guess you could easily find a C.C. supply of 150mA for a voltage range of 10-35V. And if you have more strips in parallel 1A C.C. also exists.

Take a look here:

https://www.instructables.com/id/Turn-a-broken-22-d...

0
Yonatan24
Yonatan24

5 years ago

That's so EPIC!

I've been wanting to do this for a long time but I can't find flat-screen TV's anywhere :(

0
rec2hd
rec2hd

6 years ago on Introduction

it work's fine with LCD panels too. but one has to be very carefull with the AC cord voltage and the HVAC voltage to the neon tubes.

0
tomatoskins
tomatoskins

6 years ago on Introduction

This is a great idea! Now I know what to do with those old tv's I have lying around.

0
fefc
fefc

Reply 6 years ago on Introduction

Thanks! Just be careful is you have non LED tv's, those will have neon back light and may use high voltages (1000V).