Author Topic: Artists Lightbox from 40" SAMSUNG LCD HDTV, Advice Needed  (Read 1773 times)

Offline WarriorPoet2020

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Artists Lightbox from 40" SAMSUNG LCD HDTV, Advice Needed
« on: December 02, 2012, 01:54:18 PM »
So, my pastor's HDTV got whacked by his kids and he decided to let me have it after we found out replacing a broken LCD is about as much as buying a new HDTV.  Long story short, I took it apart with an artist friend and we found something that looked suspiciously like the heart of a glorious lightbox inside.  I already found this thread, http://madmodder.net/index.php/topic,2780.msg34777.html#msg34777, which let me know that this kind of conversion is possible.  However, I have just enough experience with electronics that I can take them apart, see what connects to what and read a few of the symbols on the cards; so I thought I'd ask for specific advice from the more experience folks here.

The goal of this project is to make a lightbox that can attach to the underside of a glass-topped desk and switch on an off conveniently.  A rheostat would be nice, but I'm really not sure if those work with flourescent type lighting.

From studying the boards I figured out that the board responsible for running the backlights connects to port CNI801 on the power supply.  There I found a convenient little chart that lists the power blend for CNI801 as HIGH(273V) AC at 1.12 amps and LOW(193V) DC at 1.12 amps.  At least, I thing the sine wave symbol means AC and the solid line over the dashed line means DC.  From this I presume I just need to feed it the desired power, somehow...

That's about where I'm stuck.  I could possibly just hook all the necessary boards together in a jury rig, but I'm kind of worried about all the frame connections the boards appear to have for circulating electricity back through the frame of the TV.  I don't want to blow any of the circuits or cook myself.

Serious help is much appreciated.  I attached a number of informational pics below.

Offline BillTodd

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Re: Artists Lightbox from 40" SAMSUNG LCD HDTV, Advice Needed
« Reply #1 on: December 02, 2012, 03:06:55 PM »
I have some experience with these:

You'll probably have a DC power pair (could be 12v ?) and at least couple of control wires: one to enable the driver (i.e. switch it on) and another output to tell the main controller that the lamp is working OK . There may be another 'economy' input  that will dim the tubes, and a 0V line.


The control lines are typically ttl level i.e. 5V,  but could be 3.3v 

You may be able to trace the wires back to the main control board - with luck it might have a PCB legend that will tell you what wire does what.

Bill

[edit]
Quote
but I'm kind of worried about all the frame connections the boards appear to have for circulating electricity back through the frame of the TV.

These will be earth connections (i.e. they connect to pad around the board mounting screws) they should be connected to the chassis. The whole chassis must be connected to your mains earth or completely isolated in a plastic box .

Bill

Offline BillTodd

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Re: Artists Lightbox from 40" SAMSUNG LCD HDTV, Advice Needed
« Reply #2 on: December 02, 2012, 03:13:59 PM »
P.S can you reduce the size of your pictures to say 1024x768 - take close-ups  or crop to the detail

Bill
Bill

Offline kwackers

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Re: Artists Lightbox from 40" SAMSUNG LCD HDTV, Advice Needed
« Reply #3 on: December 03, 2012, 06:01:20 AM »
You want to leave as much in place as possible.
If the problem is that the LCD unit is broken then you should just be able to remove the LCD and put it all back together (replace the LCD with a sheet of glass).
The controller can't tell if the LCD panel is missing so turning it on should simply switch on the backlight. You should then be able to adjust the brightness with the TV remote control.

If you've got this far but want to remove the controller (it may turn off if no TV signal appears within a short time) then you should now be able to measure what's going into the inverter.
You'll be looking for two main signals, enable and brightness. Brightness has (up to now for me) always been a PWM signal - you'll need to make something that creates that. Enable is just a logic line. For power try to keep the existing power board.
Once you've got those lines figured out you should be able to remove all the superflous electronics leaving just the inverter and power supply. Don't worry too much if you can't though.