RCA TV LED32B30RQ Flashing Screen

[alfredomfr1]

Audio and Video OK just the screen is flashing

[alfredomfr1]

Re: RCA TV LED32B30RQ Flashing Screen

Any help

[budm]

Re: RCA TV LED32B30RQ Flashing Screen

" just the screen is flashing" Do you mean the backlights are flashing? This TV looks like it has one string LED.
https://www.badcaps.net/forum/attach...7&d=1430239797

The connector on the bottom left with two wires are for the backlights LED?
Pictures of the whole back side of the TV?
I hope it is not another one with bad LEDs.
https://www.badcaps.net/forum/showth...042#post557042

[alfredomfr1]

Re: RCA TV LED32B30RQ Flashing Screen

Yes, the backlight is flashing, images ok.
The connector to the backlight is the red and white on the bottom and I read
60v when disconnected and 36v connected.

[alfredomfr1]

Re: RCA TV LED32B30RQ Flashing Screen

When tv turn on I have 24v at led connector which rise to 36v after the light show

[aerthixx]

Re: RCA TV LED32B30RQ Flashing Screen

Was a solution ever found for this problem? I have same model and same problem.

[ogad80]

Re: RCA TV LED32B30RQ Flashing Screen

Hello I just wanted to find if this problem has a solution because I have 3 of the same model and 2 of them are doing the same flashing screen deal. Thanks in advanced!

[johnboy1313]

Re: RCA TV LED32B30RQ Flashing Screen

It's the LED strings inside the panel. One or more of them is faulty. I recently opened a set with a broken screen that had flashing backlights and found one of the three strings had multiple LEDs that weren't lit. It looks like each string of 12 LEDs is actually two parallel strings of six LEDs in series. I have 2 good strings available. PM me if you're interested.

[hawaiianeye]

Re: RCA TV LED32B30RQ Flashing Screen

i also have experience with this model of tv. i had one come in with this same problem. the backlight flickers very fast and constantly from as soon as the tv is turned on. but otherwise everything seems ok. the voltage measured at the led drivers was also around 60v when unplugged from the leds and it was a fluctuating voltage between 36 and 37v when it was powering the flickering led's

now heres the crazy part i dont understand:
when i "dummy tested" the psu (connected the 5vsb line to the ps_on pin through a 1k resistor, and also another 1k resistor connecting the 5vsb line to the BL_on-off pin to trick a power supply to turn on without the motherboard connected and power the backlights independently.)
anyway when i dummy tested the psu, the lights come on just fine and stable. the voltage is steady at 38v.
so i concluded that there must be some problem with the motherboard that causes the psu's voltage to fluctuate and causes the led lights to flicker.
the screen on this tv was badly cracked anyway so i decided to part it out and put all the parts except the motherboard up for sale on ebay.
but the thing is..something got lost in translation with my worker that actually makes the listings, and he ended up listing all the parts as if the tv was fine. no mention of the flicker. and all the parts sold and none of them complained or returned the part.

so the motherboard may have been good after all.
so what can cause the led's to flicker like that if i can dummy test the board and get them completely stable?
is the dummy test somehow incomplete in its ability to diagnose?

anyway so i have another of these tvs i just got recently and it has a decent screen (not cracked) so i want to fix it. its doing the exact same thing as the first one. i can get the leds to stay on using the dummy resistors, but when the motherboard is connected and sending a picture to the screen, the led voltage fluctuates and the led's flicker.
too bad i sold all those parts because swapping them out here would be nice...
i believe i still have the led strips around...didnt sell those.

this is strange behavior isnt it? how can the motherboard cause the psu to fluctuate the voltage to the backlights? doesnt the motherboard just tell the psu to turn them on or off, and thats the
end of it?

i look forward to hearing your insights

[budm]

Re: RCA TV LED32B30RQ Flashing Screen

Did you look at the dimming control signal? When you do the dummy test, the backlights will be at max output current drive for the LEDs. You can try disconnecting the dimming control line but still have every thing hook back up to see what happen.

[hawaiianeye]

Re: RCA TV LED32B30RQ Flashing Screen

i dont see any pin that says dimm (but i have seen it on other boards)
there are only 2 pins that seem to control the backlight. on/off and something called adj.
on/off is 0 when off and ~5v when on
adj is 1.41v when everything is connected normally and the backlight flickers
adj is .59v when under dummy test and backlight is stable.

is adj the same as dimm or am i looking at the wrong thing?

[hawaiianeye]

Re: RCA TV LED32B30RQ Flashing Screen

holy cow, budm... youre a genius! again!

i guess adj is the same as dimm cause i pulled that one wire and now the backlight is stable and picture looks great.
what is that thing even doing? does this mean i wont be able to change brightness settings in the menu?
what if any are the consequences of running a tv like this for long term?

thanks for the tip!

[budm]

Re: RCA TV LED32B30RQ Flashing Screen

The DIM/ADJ signal is from the main board, I do not know if it uses PWM or Analog dimming, What you can do is to hook it back up and adjust the backlights level to see if you can set it to 0.59V. I expect the higher the Voltage = the higher backlights level, it seems to me the LEDs are failing so at high backlights level (more current flowing through the LEDs, more heat generated) they start flickering.
Most TV these days have Backlights level setting and the Brightness setting which are not the same. You always want to run the backlights level as low as you can to extend the LEDs life. So if 0.59V is for less backlight level then it will be OK to leave that wire off.

[hawaiianeye]

Re: RCA TV LED32B30RQ Flashing Screen

well i put the tv back together already but i think in the menu of this tv i cannot actually adjust the backlight level...only brightness which just adjusts the pictures exposure not the voltage to the leds

[budm]

Re: RCA TV LED32B30RQ Flashing Screen

Then you will just have to see how long the LEDs will last then. For 32" RCA I would not worry about it much, use it until it dies.

[hawaiianeye]

Re: RCA TV LED32B30RQ Flashing Screen

yup. thanks

[ogad80]

Re: RCA TV LED32B30RQ Flashing Screen

Can you guys post the solution with pictures if possible, kind of a noob here. Thanks

[ogad80]

Re: RCA TV LED32B30RQ Flashing Screen

This is the conclusion that I came up with using your (HawwaiianEye & BudM) description. Can you guys verify this please I got 3 of these TV sitting in the closet waiting for repair. Thanks guys.

[budm]

Re: RCA TV LED32B30RQ Flashing Screen

The one for the ADJ pin is the one that needs to be disconnected, so yes the one you marked in red is the one.
BTW, you need to check those electrolytics caps in that section since the board got very hot as you can see that the board has dark brown around diode D400, they caps may have dried out due to the heat.

[ogad80]

Re: RCA TV LED32B30RQ Flashing Screen

I will get those checked but, holy crap all my three of my tvs are up and running!!!! Millions of thanks I was about to replace them now that they put them on sale this time of the year.