Sharp LC-40LE824E - Flickering backlight after approx. 1 hour of operation

Hello,

I have a TV Sharp LC-40LE824E, for several days I have had a flicker of the screen after about 1 - 1.30 hours of viewing. After switching off the TV for some time and switching it back on, the effect disappears but returns after about 1 hour.

Will erasing errors in the service menu help something? How to get to this menu?

Possibly if it's the hardware fault, the reason lies in the power supply?
The power supply model is: DPS-126CP-1A.

I am asking for a solution to the problem.

greetings
Artur

Here in this SM is not described Link or the second commonly available ftp://helpedia.com/pub/temp/datasheets/monitors/Sharp/Sharp_LC-40LE814E_LC-46LE814_LC-40LE824E_LC-46LE824E_[SM].pdf

Verify and give what you have at home: descriptions with T-con, matrix and power supply.
Provide a set of integrated circuits in the power supply.

I do not know what I'm doing wrong but I can not get to MS.

Arczizioom wrote:

I do not know what I'm doing wrong

For now, it's probably the wrong model TV

In fact, two numbers escaped me. I've already corrected.

Arczizioom wrote:

I do not know what I'm doing wrong but I can not get to MS.

Do you think a little?
Well tell us how do we know what you are doing wrong, if you do not know what you are doing?
Or maybe fortunately you can not enter?

Arczizioom wrote:

Will erasing errors in the service menu help something?

No.

Arczizioom wrote:

Possibly, if it's the hardware fault, the reason lies in the power supply?

Maybe.
In others too.

Maybe you just need to use basic diagnostic tools? At least for the beginning.

mirex wrote:

Maybe you just need to use basic diagnostic tools? At least for the beginning.

Friend, what do you propose?

Multimeter. Possibly only a voltmeter.
The oscilloscope to check the backlight control would also be suitable.

You could still raise the temperature, you might not have to wait an hour for special effects.

I had such a defect and the backlight itself was to blame.
The fault occurred differently once in an hour and sometimes once in a few days.

Buddy check the temperature of the black heat sink in the RUNTKA685WJQZ power supply. Take a fan and chill it. The KIA378R12PI stabilizer is overheated under it. Alternatively, to determine the cause, heat the heat sink with a hot air dryer or dryer, otherwise it will dissipate the heat with the cover and otherwise without it. You will not have to wait an hour. Check if the backlight starts going crazy and returns to normal after cooling down. Read my last post in the topic www.elektroda.pl/rtvforum/topic3047339.html
For the future:
Regarding the service menu on on TV, you hold the button for 6 seconds until the LED on the TV flashes. Only then the inverter switches off completely. Later normally as in the service center;
VOL-, INPUT, PWR to K mode then
VOL-, CH- to service mode.

If it turns out that after removing the power supply from the TV later does not want to catch the backlight the same way on the TV switched on you hold PWR until the LED flashes, then you press CH + and PWR.

But do not bury anything. Already, not one TV was slaughtered in MS and if there is no need to advise against going there. If the fault confirms, the backlight errors caused by this do not write down, at least I did not meet with it. The above-mentioned solution will solve the problem. Write or helped Regards!

I think you're right, after heating and cooling the heat sink, the effect appears or disappears. I will order this stabilizer and replace it.

The stabilizer you still have a good reason for overheating is a terrible heat sink. You'll admit it is crap. Most likely, he let the thread gently. Be careful that when lifting the heat sink, do not release the noun of the Chinese ap6679g because it is expensive and hard to reach. The stabilizer must be kia378r12pi has max Io = 3A and the regular KA78R12 has only 1A. It's best to settle the matter by changing the paste and buying longer screws and spring washers with a nut and screw it over, and thread the thread even with nail polish
Alternatively, if the TV is exposed to poor airflow, add passive or active cooling.

And this is already strange, because after the appearance of the defect I changed the paste on the MX2 and tightened everything to the max and on all 3 heat sinks.

I will try to tighten something to this heat sink. Preventively I drilled some holes at the very top of the case in the warmest place for better cooling.

In addition, I had the same symptom as you, regarding the flashing of the matrix backlight after turning off the TV.

The stabilizer you have available at north.pl is cheap. The most important thing is that the topic seems to be solved. As a symptom, I can still give up the momentary lack of signal by HDMI from time to time and the ECO system's vortex. And when the stabilizer is gone, no voltage 12V on t-con. 2 long and 5 short diodes flashing.

I did not notice the lack of video on HDMI. And on the ECO system the fault intensified.

I will replace the stabilizer in a preventive way and improve cooling.

Thanks for the help.

Check / replace the C7972c capacitor. For my part, I would like to add that the RUNTKA685WJQZ and the RUNTKA686WJQZ twin units are used in different Sharpa TV models and the symptoms of the feler are identical. The topic will certainly help someone else.

Hello,

I'm coming back with the topic. Despite the efforts to cool as much as possible, the black heat sink still occurs. I replaced the previously indicated stabilizer and increased the radiator surface. Additionally, getting rid of paint in places where elements meet.

An additional defect that I observed after some time when it blinks stops and locks at the highest brightness, the brightness adjustment in the TV menu does not work.

The conclusion is that some TV element consumes more power while overheating this stabilizer.

At the moment the only thing that comes to my mind is to add a fan. The only question is what to feed it to turn on when turning on the TV and turned it off when turning off the TV. It's best that it is not 12V and about 8V.

Possibly where to look for the fault?

greetings
Artur

Provide ICs in your PSU.


RUNTKA686WJQZ to DPS-141CP 1A> somewhere I have MS, then I will find and give it in diagrams
IC7601 DDA002C
IC7702 DDA003A-5G240
IC7801 NCP1608 * PFC



__________
In Sharp LC-40LE820M with RUNTKA687WJQZ the problem was with IC7003 (MIC5209-5.0YS) + elements C7928, C7961A, D7907, R7939, ... * ambient measurements



(' ') This stabilizer heats up because you put on "classic" >> it has to be LDO (low-drop) small voltage drop between input / output. IC

lisek wrote:

(' ') This stabilizer warms up because you assume "classic" >> it has to be LDO (low-drop) small voltage drop between input / output. IC

Who told you that he was moving at all?

The stabilizer was warming up. And this one is changed with the same designation as the one, so this is not the problem.

KIA378R12PI
https://north.pl/karta/kia378r12pi-uklad-scalony--ic,729-TV-3732.html

Wrzucciłem SM DPS-141CP 1A / * also RUNTKA686WJQZ Link_ DPS-141CP 1A / also RUNTKA686WJQZ

Added after 39 [minutes]:

About which IC we speak * unless about the same IC

If you read what people have to say, not just the titles of topics and the first sentence, you would know and not poison.

In addition, there is a specific effect, and the exchange itself has not changed anything.

It's just that ... conclusions @smkowiecm not necessarily right. Though he supposedly helped in his case.
I will ask, so naively, because it seems so simple that it's funny ...
- what prevents you from removing the stabilizer from the shared heat sink and giving it to another. Or even screw to the plates. And then continue to look.

On the forum I found information that after processing the power supply will go eg RUNTKA847WJN1. Can anyone confirm this information?

After processing, many can "go".

Can you confirm unambiguously , that the cause of this fault is the overheating stabilizer 12V ??

Or maybe in a different way ... though timidly, I will ask.
What connection with the backlight have the elements on this heat sink?

VR7701 check or increase gently value.

What should be its standard value?

About 3k, but with the aging of the diodes, the value of the diode current changes and the value of r must be increased.

With me it was 2.11k and I increased it to about 3.5k. After this treatment, the backlighting slightly increased the brightness. The question is how to choose the right value?

With the aging of the LEDs, the operating point changes. You need to choose the value of PR so that it does not flicker.

The issue still exists. To make it more interesting if the TV is on the footer and the space behind the TV is bigger then it works correctly even 2-3 hours (I have not tested more). I've run out of ideas for him.