Riddled TV Repair Forum

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

Hello, we bought a RCA led52b55r120q about 3-4 yrs ago. In the past 2-3 weeks the screen would turn black, while we were watching a show. To fix this we would unplug it for a few seconds and plug it back in and it would work. In the past 2 days the screen is just black and the unplugging of the TV doesn't work any more.

So, like most people I searched the internet and came across a youtube video talking about testing the making sure the voltage is right here and there. I tested the main plug rail and I got all the correct voltages. But when I tried to locate the LED lights, I had a hard time finding it. But, with a bit of little looking around I saw a CON4 connection that has these pins GND, ADJ, BL-ON. I'm guessing BL-ON should be back-light on. I was getting around 5v there.

So my 1st question is does CON4 control the LED stuff and if so, what is the proper voltage. Is 5v correct?

In the picture CON4 is the 3 wire plug.
http://imgur.com/a/md7uY

My second question would if that is not the issue what would be.

I'll include some other pictures as well to help you and I out.

Video Processing
http://imgur.com/a/FLdym

Controls
http://imgur.com/a/7hWSU

Whole layout
http://imgur.com/a/yOnYL

Thanks

Google

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

You don't say if the whole set turns off completely or if audio continues. If it is the second, shining a flashlight very close to screen may reveal some video, in which case the LEDs themselves may be involved.

BL-ON at CON4 on the Power Supply / LED board is the control signal for the LEDs at CON5. It should be coming from the Main board and should have two voltage states - One value with TV in Standby and a different value once the TV Power button has been pressed. The third board you pictured is the Tcon board.

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

So when the TV is off there is no sound and while the TV is on there in no picture only sound.

But, I did do the flash light trick and press the input button. I knew where that should appear at and I can see some text.

So, I'm guessing its the LED. Do you know where I could get some replacements at.

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

First be sure your switching (BL-ON) AND The LED power supply voltage(s) are present. Both MUST be on and STAY on when the TV is on.

https://imged.com/led-strips-e227809-c-for-rca-led52b55r120q-tv-set-of-12-508901.html

which then using the 'e' number leads to:
https://www.ebay.com/i/191980620184?chn=ps&dispItem=1

12 strips versus 8 strips do NOT match, so you should open the panel to confirm: that one (or more) LEDs have failed, how may strips are present and record any numbers on the strips themselves.

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

Thank you very much. I'll double check the voltage on the BL-ON, with the TV on and off.

Google

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

OK I doubled check the BL-ON with the TV off I get 0 volts and with the TV I get 5 volts.

I re-read your statement again "The LED power supply" where is that located at. Is that the CON5?

I'm going to check the LED to see which one I have

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

I thought I would try to test the LED connection the positive and the negative (the red and white wire on CON5) to see what reading was and all I saw was the voltage dropping. So, I guessed I was doing it wrong.

JTS1957 · Joined: 21 Jan 2009 Posts: 2395 Location: Far, Far Away

The LED power supply voltage(s) at CON5 is correct.
In addition to measuring both in standby & TV On with CON5 plugged in, you might see if there is any difference measuring at the 'pins' with CON5 unplugged.

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

I didn't get any difference in reading when I unplugged CON5.

I have notice from plugging and unplugging the TV, I can see a quick flash of light every once in while.

My LED 14 across by 6 down.

So, from here are you still leaning towards the LED is bad

lincxx · Joined: 13 Aug 2017 Posts: 8 Location: USA

I took a quick video of the flash

https://www.youtube.com/watch?v=wU8FyO98L_g

happens around the 5 second mark