Rca led50b45rq

[Gorrillasnot]

Hello,

When plugged in the TV has a red standby light.
I press the power button and the standby light goes out, a grey bar flashes across the bottom of the screen, then nothing but a black screen and pressing the power button does nothing.
Unplug and then plug TV back in is only way to get standby light back on.

I will try to take pictures of the TV soon.

This TV doesn't have a plug with voltages listed so I am not sure where to measure.
can someone point me in the right direction on what pins to measure for voltage?
attached will be a photo I borrowed from shopjimmy of the psu board.

From searching google it seems people who had similar issues with this TV traced it down to a faulty mainboard.

any info would be appreciated.

thanks

[budm]

Re: Rca led50b45rq

RCA RE46HQ1290 Power Supply / LED Board
http://www.shopjimmy.com/rca-re46hq1...led-board.htm#

Leave the meter probes on between the two legs of capacitor EC9, turn on the TV and take the notes on the meter, and after 5 seconds,
Do the same again on caps EC12, EC13.
We also need good clear pictures of the bottom side of this power supply-LED driver board without the black insulator sheet so we can clearly see the traces on the bottom side of the board.

[Gorrillasnot]

Re: Rca led50b45rq

thanks for the reply budm.

When first plugged in the voltage on EC9 fluctuates then falls to 0. When the power button is pressed it goes to a steady 12.2v.

EC12 and EC13 has 5.1v when plugged in and when the TV is turned on there is no change, it stays a steady 5.1v.

I haven't had a chance yet to remove the power board to take pictures of the back of the board, but will do tomorrow.

From googling it seems like a common problem with this TV is a faulty main board..Do you think that is likely the problem with my TV?

thanks

[budm]

Re: Rca led50b45rq

Oops I gave you the wrong cap number to check, it is cap EC6, sorry.

[Gorrillasnot]

Re: Rca led50b45rq

EC6 is 0v in standby and 53.4v powered on.

[budm]

Re: Rca led50b45rq

OK, good, next will be the Voltage on between the two legs caps of the Boost converter output EC201, EC202 (Also look for the capacitance and Voltage rating of the cap, I cannot tell from the picture as to what the ratings are).
Then we need the DCV between chassis GND and each one of the L+ of the connector CON5.

[Gorrillasnot]

Re: Rca led50b45rq

EC201 Starts out at fluctuating on the meter in standby then when the power button is first pressed the meter stops briefly at 56v then when the screen flashes the meter spikes up to 128v then starts falling.
EC202 is similar at 55.4v then spikes to 136.2 when screen flashes.


CON5 I get 54.1 on both L+ test points in standby and 139.2 and 132.7 when powered on.


I don't see the ratings printed on the caps, all I see is AiSHi 1338JPET.
They are bent over and glued to the pcb..should I try to pry one up?

thanks

[budm]

Re: Rca led50b45rq

OK, the boost converter that boosts the 55V to more than 100V is working, but it goes into shutdown.
No need to look up those two caps rating at this point.
I think more likely you have LED problem due to not equal readings of the L+s, I need to look how the LED strings are connected so I need the pictures of the whole bottom side of the board and the closed up on the bottom side of the board around CON5.

[Gorrillasnot]

Re: Rca led50b45rq

So it's looking like a bad LED strip?

thanks

[budm]

Re: Rca led50b45rq

OK, the L+ for each LED string are directly connected together so the reading of both L+ should be the same.
We need to check the DCV of each L- next to see what you get when the screen flashes on.
There are two drivers for the LED strings.

[Gorrillasnot]

Re: Rca led50b45rq

LED- thats just to the left of where it says CON5 (has white wire attached) has 0v standby and goes to 47.1v very briefly as the screen flashes (for less then a sec).

LED- thats just to the left of where it says NC (has black wire going to it) doesn't show any voltage at all either in standby or when powered on.

Also when retesting the LED+s they fluctuate..I did 3 back to back tests on each LED+ and got between 132v and 139v on each one of them when the screen would flash.

thanks

[budm]

Re: Rca led50b45rq

'LED- that is just to the left of where it says NC (has black wire going to it) doesn't show any voltage at all either in standby or when powered on.'
OK you found the problem, that string has open circuit.

[Gorrillasnot]

Re: Rca led50b45rq

That means to fix it I would need to replace the bad LED bulb or strip?

sorry I am still very much a newb and this is the first LED TV I have worked on.

[budm]

Re: Rca led50b45rq

The hard part will be taking the panel apart to get to the LED strips without damaging the LCD Glass panel.
I do not know if this TV is back-lit or edge-lit.

[Gorrillasnot]

Re: Rca led50b45rq

that's what worries me is the glass panel. It looks like it is very delicate.
The TV belongs to a friend of mine so I probably will pass the info on to him and let him take the risk of breaking the panel.

thank you very much budm for all your help.

[budm]

Re: Rca led50b45rq

50" is a big panel, you will need lots of room and may be a second person to help.
Also tell your friends to turn down the backlights level in the on screen user menu setup down as low as possible in the new TVs.

[zblad]

Re: Rca led50b45rq

Id hate to hijack your post but i have the exact same issue all my voltage readings are similar except the LED ones you did last i get a spike of 27v when i power the tv on. I might be measuring wrong tho how do you measure the LED -? I would appreciate any help did you end up buying new LED strips? If so where?

[Gorrillasnot]

Re: Rca led50b45rq

Id hate to hijack your post but i have the exact same issue all my voltage readings are similar except the LED ones you did last i get a spike of 27v when i power the tv on. I might be measuring wrong tho how do you measure the LED -? I would appreciate any help did you end up buying new LED strips? If so where?

With the TV plugged in, but turned off I placed my black probe on a chassis ground and red probe on LED- then I pressed the power button and watched for any voltages or spikes. In my case one of the LED- voltages was 0 indicating a problem.

I never did fix the TV. It didn't belong to me and I didn't want to be responsible if the screen cracked while taking it apart.

[zblad]

Re: Rca led50b45rq

Hey thanks for the reply i dont think i get any voltage when i measure like that... So i wonder if its my powerboard... Its weird because if you try unplugging it and plugging it back in after 40 times the tv will come on sometimes and stay on.

[zblad]

Re: Rca led50b45rq

Another strange thing is if i plug the tv in the red light comes on i hit power it goes out the tv then blacks out and i cant hit power again i have to unplug it from the wall. If i unhook the connector going to those LED pins i can turn the tv on and off.