RCA RLED6090 backlight goes affter 10 minutes

[Anooc7]

Hi,
I have this rled 6090 led tv which has this backlight issue, When I change it to energy saving mode and tv works fine , All the other mods has this issue. I have entered the service menu by pressing input + 2580 and reduced the backlight to 50% . But as soon as I exit from that service menu it goes back to higher levels. (Since there is no options to save it) . There is a small ic near led drive section a dual opamp , as358m . Is it serves as a controller for backlight? How do I reduce the backlight level using an increased current sense resistance or something like that? The psb is ER991D
Checked both the led strip end and both works with same 170v .
Thanks in advance

[CityZen]

Re: RCA RLED6090 backlight goes affter 10 minutes

LED brightness is typically adjusted by PWM (pulse width modulation).

[neilc6]

Re: RCA RLED6090 backlight goes affter 10 minutes

I don't touch RCAs any more. You can't find new strips for these which is the correct repair. Strips could still fail in the future even with the backlight level lowered.

[Anooc7]

Re: RCA RLED6090 backlight goes affter 10 minutes

LED brightness is typically adjusted by PWM (pulse width modulation).

I couldn't find the schematic, very unfortunate on that.

[Anooc7]

Re: RCA RLED6090 backlight goes affter 10 minutes

I don't touch RCAs any more. You can't find new strips for these which is the correct repair. Strips could still fail in the future even with the backlight level lowered.

Yeah , so true. Since every strips works I wouldn't be able to find the faulty one too unless I have a single oem strip to replace, and its a headache.

[CityZen]

Re: RCA RLED6090 backlight goes affter 10 minutes

If nothing else, you could add some diodes inline with the LED outputs. Each will drop the voltage a bit and thus dim the LEDs correspondingly.

[lotas]

Re: RCA RLED6090 backlight goes affter 10 minutes

If nothing else, you could add some diodes inline with the LED outputs. Each will drop the voltage a bit and thus dim the LEDs correspondingly.

It is not necessary to reduce the voltage, but the current that is supplied to the LEDs.

What is (name) LED driver U303 worth?

[alfatv]

Re: RCA RLED6090 backlight goes affter 10 minutes

You have 2 possibilities here:
1. Proper repair
2. Band aid

For #1 you need a good LED tester with high current. Check each strip separately, the bad one should have at least higher voltage drop or maybe even go open. Then with this method you can find that single LED.

For #2 you can just use eco mode. If you reduce current, the effect will be almost the same.
If you really want to lower the current, I think R5501 is current sensing resistor.
Just don't do it for customer especially if you charge money.

[Anooc7]

Re: RCA RLED6090 backlight goes affter 10 minutes

You have 2 possibilities here:
1. Proper repair
2. Band aid

For #1 you need a good LED tester with high current. Check each strip separately, the bad one should have at least higher voltage drop or maybe even go open. Then with this method you can find that single LED.

For #2 you can just use eco mode. If you reduce current, the effect will be almost the same.
If you really want to lower the current, I think R5501 is current sensing resistor.
Just don't do it for customer especially if you charge money.

Thank you so much, I will try to modify the current sensing resistor. So do I need to increase its value? (It is a 0.8 Ohm resistor so how much do I need to change its value? )The customer is happy to repair it cheap but he need a bit more brightness than eco.
Thanks

[alfatv]

Re: RCA RLED6090 backlight goes affter 10 minutes

As I said, don't do it, just return and don't charge anything.

[Anooc7]

Re: RCA RLED6090 backlight goes affter 10 minutes

For those who have similar issues here is the fix, I have added 3x 0.6 ohm 2 watt resistors (I didn’t have any 2ohm single ones) in series with R5501 and It works great. Your human eye will never notice any difference at all , and its brightness setting is still in the middle and sufficient for my happy client . I did increase the brightness to 80% and it still worked without any issues.

[aleks555]

Re: RCA RLED6090 backlight goes affter 10 minutes

Hi Anooc7,

I have a similar issue with the same power supply board. I want to try your solution, but can't find resistor R5501 on the board. There is RS501 though (letter S instead of digit 5). Could it be the one?

[nomoresonys]

Re: RCA RLED6090 backlight goes affter 10 minutes

yep

[aleks555]

Re: RCA RLED6090 backlight goes affter 10 minutes

yep

thanks!

[nomoresonys]

Re: RCA RLED6090 backlight goes affter 10 minutes

Very good work by the way Anooc7

[RinusB]

Re: RCA RLED6090 backlight goes affter 10 minutes

Did this finally stop the backlight from going off? My RCA RTU6549 (Canadian model 4K likely from Walmart) also goes off but not at the same times.
Is heating up causing a separate problem or? Also, where the voltages to the mail board are marked 24v on this board but the output is actually 12v on both pins. The TV works fine but then shuts off the screen and the sound stays on. I cannot see a faint image at all.
I replace the resistor(2 in series) in question to 2.3 ohms. In the circuit the value it measures is only 0.3 ohm. The diode is good.

[alfatv]

Re: RCA RLED6090 backlight goes affter 10 minutes

RinusB, please create a separate thread, your TV model number is different and the problem could be different as well.

[aleks555]

Re: RCA RLED6090 backlight goes affter 10 minutes

Did this finally stop the backlight from going off? My RCA RTU6549 (Canadian model 4K likely from Walmart) also goes off but not at the same times.
Is heating up causing a separate problem or? Also, where the voltages to the mail board are marked 24v on this board but the output is actually 12v on both pins. The TV works fine but then shuts off the screen and the sound stays on. I cannot see a faint image at all.
I replace the resistor(2 in series) in question to 2.3 ohms. In the circuit the value it measures is only 0.3 ohm. The diode is good.

I have the same issue with RCA RTU6049, I know it's a different model than OP, but it shares the same PCB ER991D, the PCB picture also matches exactly. So I think my report might be relevant to this thread.

Increasing resistance on RS501 didn't fix my problem. I increased resistance to 2ohm, then to 4ohm, no changes in symptoms.
At this point I gave up, returned to original resistor and use TV in eco mode. Now it turns off 'only' once a day or so.

[RinusB]

Re: RCA RLED6090 backlight goes affter 10 minutes

I may agree that the resistor did nothing for me either but I left that new combo of 2.5 Ohm in placer.
Then as I had it plugged in and used HDMI 1 from my cable supplier PVR and a 12' HDMI cable it stayed on for three hours today and when I changed to HDMI 4 it turned off after just 15 minutes.
I have more to add to all this and that is the issue with the 120 volt from the wall or extension cord.
My Sony 60" will restart or turn off when plugged into an extension cord with a power bar.
Pretty much any call to a supplier's help service starts this way: Is the TV plugged into a wall socket? Not a power bar, three way or more plug or an extension cord? If so plug it into a wall outlet that is not shared with anything.
I understand that pulses in the power supply can affect poor design (poorly filtered) circuit boards.
Maybe any of this applies to so many RCA TVs. Rather than changing the resistors I may replace the capacitors. But yes, the Eco mode looks fine to me also and the voltage on the LEDs that way is only 124v rather than 154v.

[nomoresonys]

Re: RCA RLED6090 backlight goes affter 10 minutes

Lotus gives the explanation simply and clearly here, post #32: https://www.badcaps.net/forum/showthread.php?t=113404