Q: Universal Power Supply Boards for TV LCD/LED backpanes

[Robin Ingenthron]

Our company is manufacturing backlight signs for restaurants, and our current process involves keeping the original TV power board to light the backpane.

We think the TV powerboard is "overkill" to just run the lights and also has more value sold for another TV.

Does anyone have experience with Universal power boards like these ones (sold on Alibaba)?

http://www.finder.com.cn/Products/Details/LCDPower.htm

Finally, what's the best vocabulary word when the OLED crystal sheet is removed and you have only the frame and compact fluorescent / LEDs?

backpane? backlight? backpanels? backplanes?

fairtraderecycling.org
Robin at WR3A dot org

 

[John-Del]

On Thursday, September 28, 2017 at 11:56:53 AM UTC-4, Robin Ingenthron wrote:

Our company is manufacturing backlight signs for restaurants, and our current process involves keeping the original TV power board to light the backpane.

We think the TV powerboard is "overkill" to just run the lights and also has more value sold for another TV.

Does anyone have experience with Universal power boards like these ones (sold on Alibaba)?

http://www.finder.com.cn/Products/Details/LCDPower.htm

Finally, what's the best vocabulary word when the OLED crystal sheet is removed and you have only the frame and compact fluorescent / LEDs?

backpane? backlight? backpanels? backplanes?

fairtraderecycling.org
Robin at WR3A dot org

Yikes. Do you mean that you use discarded TVs, remove the LCD, and use the back light as a basis for a sign?

If that's what you're doing and don't want to use the existing power/LED drive board, take a current measurement of the existing LED array with the TV running. Build/buy a current regulated supply that will supply the LED array with about 30% less current than the TV did (those are overdriven and have a very short life as installed). The voltage required can be up to 300 volts depending on how many LEDs are used and if they're all arranged in series, so every application is different.

Using the original supply can be easier, but you will have to externally enable the back light on command line and most of these power supply boards won't turn on the LEDs unless they receive a PWM signal from the main for the brightness feature. You'll either need to keep the TV main board functioning or build a pwm signal generator.

If you get the run current wrong on the LEDs, they won't last.

Not sure what you're trying to say about OLEDs, but we refer to the screen assy sans LCD display as a light box, although there's no standard definition that I'm aware of.

I think a far easier plan would be discard the TV components entirely from inside the light box and buy LED strip lighting and a control box (Alibaba, ebay). This way you can be sure you won't over drive the LEDs.

 

[Robin Ingenthron]

Thanks John-Del. That is similar to the instructions we got from the Ghana Africa guy who makes these. I was hoping that the Alibaba link ( finder.com.cn/Products/Details/LCDPower.htm ) will work.

Here is a link to a Powerpoint done in Ghana by the USA apprentices we sent to work under Master Technician Karim Zakaria.
https://docs.google.com/presentation/d/1nxPz3F66ngYVHUVwjtSDPP51EafaqhwHCM9LG0Qs2vQ/edit?usp=sharing

 

[John-Del]

On Wednesday, October 4, 2017 at 4:26:03 PM UTC-4, Robin Ingenthron wrote:

Thanks John-Del. That is similar to the instructions we got from the Ghana Africa guy who makes these. I was hoping that the Alibaba link ( finder..com.cn/Products/Details/LCDPower.htm ) will work.

Here is a link to a Powerpoint done in Ghana by the USA apprentices we sent to work under Master Technician Karim Zakaria.
https://docs.google.com/presentation/d/1nxPz3F66ngYVHUVwjtSDPP51EafaqhwHCM9LG0Qs2vQ/edit?usp=sharing

This is a lot more complicated than sourcing an LED supply and connecting it to the existing LED array inside the screen.

If you want to source a universal supply to run existing LEDs, you must be sure that it can run independently from the donor's original main board. Very few power supplies will turn on the back lights without a pwm adj/brightness signal from the main board to set LED drive current.

One that I can think of that will run independently from a TV main board is this power supply included in recent certain RCA and ProScan TVs (possibly others):

http://www.shopjimmy.com/rca-re46hq1301-power-supply-unit.htm

This supply will run and output LED drive with only AC supplied. The on command can be enabled by using a 470 ohm resistor between the power supply's standby line (pin 8) and the on/off line (pin 9) of CON2 to turn the power supply on. You'll need to do the same between pin 8 of CON2 and pin 3 of CON4 to power up the LEDs. This will enable the backlights with no input to the "adj" line although the output of the supply will be reduced (which is a good thing to ensure LED longevity).

The first problem is that this supply needs a balanced load on the LED outputs, so you'll need to divide the LED strips into equal pairs. If the donor TV has an odd amount of LED strips, this may trigger LED shutdown (some do, some don't). You may have to rewire the strips in order to present two identical loads to the two output terminals of the LED output on the power supply (CON5) Another problem is that TV power supplies adjust it's LED voltage output in order to regulate to a specific current, and so some LED strings might require more voltage to reach the required run current than this particular supply is capable of.

The point I'm trying to make is that you aren't going to be able to teach trained monkeys to do this job if you intend to make these signs in quantity.. The workers will need to possess a working understanding of electronics and basic design. Almost every job will be a custom one as there is an almost infinite number of LED TV designs in the market. If the assembler manages to get it running but doesn't monitor run current, the sign may fail within minutes or hours.

It would be far easier to buy LEDs on flexible ribbons, buy the controller that is used with these types of LED ribbons, and install these inside the screen. You can even program color changes and brightness as well as remote control of on/off with these:

http://www.ebay.com/itm/5050-RGB-LED-Strip-Decorative-Light-Tape-Ribbon-with-44keys-IR-Remote-Controller-/162535694280?var=461540370055&hash=item25d7e1dfc8:m:mw_r_9Ul6iUCkrWlmvnaFqA

If the LEDs you install have an uneven appearance on the TV screen, you can pop the lens' off the donor LED strips and carefully glue them over the dead center of the new LED.