rca rlded5078a-d

[dpcookson]

Re: rca rlded5078a-d

Update; I was able to use an old ATX power supply to supply each LED with 3.3V.
6 of the LEDs were burnt out, the odd part is that the first LED on all 5 strips were burnt out plus 1 part way into one of the strips. Would this indicate an over voltage problem?

[budm]

Re: rca rlded5078a-d

Since you did get high Voltage reading for seconds, it is telling me that the circuit is not dead.

[budm]

Re: rca rlded5078a-d

Update; I was able to use an old ATX power supply to supply each LED with 3.3V.
6 of the LEDs were burnt out, the odd part is that the first LED on all 5 strips were burnt out plus 1 part way into one of the strips. Would this indicate an over voltage problem?

You should put a current limiter resistor when testing the LED.

[CapLeaker]

Re: rca rlded5078a-d

GND lead of the DMM was on the GND circuit of the board. On power up, the voltage at the LED connector started at +0.69V then about 3-4 seconds later it "dropped" to -394V, then returned to +0.69V. With the unit powered off there is 0V at the LED connector. I suppose it doesn't matter which side of the LED circuit is positive or negative, as long as the LEDs polarity matches.

I realize that an LED is a diode but maybe I was checking them wrong with my meter, if you look at my previous posted pictures, I was connecting my leads to each copper "dot" on both sides of an LED. I tried reversing the leads but came up with an open circuit on the few random LEDs I tested, makes me think I am doing something wrong, that or every LED is "NFG".

That mean the LED driver is working O.k. (high voltage spike), however I think you have probed it not correctly... but that doesn't matter. Main thing is the circuit is working.

It doesn't surprise me that there may be 5 LED's in a row bad. Most of the time the backlight of the panel was set on 100% and that does shorten the LED life. Set it back to 60 to 75% and the LED's in the panels are going to last much longer.

Update; I was able to use an old ATX power supply to supply each LED with 3.3V.
6 of the LEDs were burnt out, the odd part is that the first LED on all 5 strips were burnt out plus 1 part way into one of the strips. Would this indicate an over voltage problem?

Since you did get high Voltage reading for seconds, it is telling me that the circuit is not dead.

x 2

You should put a current limiter resistor when testing the LED.

x 3 and that one is important! LED's supposed to be current limited not voltage limited. Even so you can voltage limit the LED, that is not correct way to do it.

Anyway... You have way to many LED's out so you would have to find replacement LED's or harvest some used LED's from a different TV.

[2cams70]

Re: rca rlded5078a-d

Looks like these critters might suit:

http://www.ebay.com/itm/New-LED-TV-B...item3ab172d4f9

Seems to be a design or LED quality problem with this TV though for it to be such a common issue. Any ideas about the root cause and modifications that might stop this in future - other than turning down the brightness. Add resistor in series with LED's perhaps?

[smuddge]

Re: rca rlded5078a-d

just for anyone else reading this. it is indeed the leds that were burnt.
I tested and had 1 that had a short and 1 that was burnt out.
changed them both with some spares I had from a bad samsung and voila.
back to working.

i changed them with a heat gun but the one with the short still wouldn't work so I ended up just cutting a part of the samsung strip and wiring it in and taping it down so it was in the right position.

let it run over night to make sure it would last and 12 hours later still going strong no issues.

thanks again to this forum and its members for helping me and saving another one from the dump.

[CapLeaker]

Re: rca rlded5078a-d

Nice follow up! Thanks!

[budm]

Re: rca rlded5078a-d

Thanks for the follow-up.
You should also turn down the backlights level as much as you can, that will extend the life of the LEDs.

[ajal14]

Re: rca rlded5078a-d

hi, I have the same issue on my TV , the same modele as your tv rca rlded5078a-d. Did you fix yours so you may help me with mine. I have doubt on the IC LED DRIVER , BD9211F,nothing coming out from it but it has the 11.8volts at pin 1.

[ajal14]

Re: rca rlded5078a-d

hi, I have the same issue on my TV , the same modele as your tv. Did you fix yours so you may help me with mine. I have doubt on the IC LED DRIVER , BD9211F,nothing coming out from it but it has the 11.8volts at pin 1.