I have a 2 year old Samsung LCD TV. Sometimes, when I turn on the TV, the backlight doesn't turn on (not even for a split second). The on/off indicator on the panel blinks 2-3 times and then goes off. At other times, the backlight does turn on and the TV works properly. Also, a couple of times the backlight suddenly went off while the TV was working normally. What component might be at fault here? If it is the inverter board, would it be advisable to get the board repaired or buy a new one?
Check for any loose soder points or loose connections with wiring sockets to backlight inverter board.
It sounds that there is some loose solder terminals to the power supply regulator board. Usually, loose solder terminals are very difficult to detect, as they will be micorscopiclly small. I reconded you to take out the power regulator board [after switch OFF the set, and unplugged it from wall AC outlet ofcouse], and resolder all suspected solder termianls, by applying a little more solder, without making any solder bridge short in between adjecent solder terminals. Be very carefull. OK
If this too do not help you, it will be best to replace the power supply regulator board with a new one as card basis, rather than making 'surgery' to it. OK.
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This is a TV power supply problem
that my be caused by some bad capacitors on the secondary section, it
is a very common problem especially for TVs that works for a long period
during the day. It can also be a back-lights inverter board problem.
You can do Samsung LCD repair
yourself if you have some electronics repair skills or you can take a
look at this video tutorial that will show you how to repair LCD TV
problems.
You-Tube video "277CUSZYjqw" placeholder (do not deletSamsung 32'' LCD TV backlight works occasi - utube.pngb>
SOURCE: Samsung LTN1765 has blinking green power indicator, but no picture or sound
Try replacing C51, a 10 microfarad 16v. surface mount electrolytic. It's near IC23 on the upper center of the board.
This part had high ESR on a couple of sets I serviced which
kept the power supply from starting.
SOURCE: Screen goes completely out.
when it blanks out, tuen the lights out in the room, and shine a flash light at the screen, see if you can see the picture, if you can, it is the inverter moard blamking out, thats the board that lights the back lights, if you cant, hit the input button on the remote, if the TV comes back with a picture, it is a problem with the main board, in paticular the componant input on the main board
SOURCE: Samsung LN-S4041DX 40 in LCD TV
Hi. You can try to go into service mode and reset the LCDTV to Factory Default. This will clear out all buffer over run's and any software related issues. It may fix the problem or it may not. If this doesnt fix the problem than you need to have a qualified Technician to look at it. The problem is in the AV circuit board, a technician who is qualified to repair electronics at circuit board level should be able to repair this problem rather quickly and inexpensively. Most technicians who do not have the expertise in repairing cicuit boards to component level would rather replace the whole AV board than repair it and this will be rather expensive.So talk to the repair shop before you drop the TV off.
Be very careful when accessing service mode. I suggest to write down all information in all areas before proceeding to a factory reset. If you do not record all values correclty you run the chance of not being able to use the TV again. To go into Factory Service mode, use the original remote and in this sequence push POWER OFF-MUTE-1-8-2-Power ON, the set will turn on and enter service mode, if you hit all previous keys correctly. If it doesnt try again. When you are done hit POWER OFF and this will exit service mode and save the data.
SOURCE: My Samsung LCD TV will not turn on, it just clicks
A Replacement Power Supply.
Parts: £80 - £110 depending on the model.
Labour: £40 (ish) little bit more with a 90 day warranty etc.
Type your model number into www.chsinteractive.co.uk for the price on a PSU.
Good Luck.
SOURCE: samsung lcd tv ltm1755b won't turn on (power light stays red)
Problem: Samsung LTM1755B with only a blinking yellow LED when you try to turn it
on.
Solution: I just had one of these come in. I opened it up, and found
the U501 capacitor a little suspicious looking, in that it had a
deformed top. It was a 470uF 16V electrolytic 105degC 10mm x 12mm. I
replaced it with a very good quality 1000uF 16V electrolytic 105degC
10mm x 16mm Nichicon UHN1C102MPD. After that repair, when I tried to
turn it on, the LED was yellow for a second, then green, then I got a
picture, and it appeared to work great. I then asked the owner a week
later how it was working, and they said it was working just like new!
I'm afraid that while their intention was good, that most the posted solutions miss the mark. Let me guide you thru the diagnosis and possible cure. This is detailed and lengthy, since these points appear often in LCD TV/Monitor repair. You may wish to warm up your soldering iron and skip to Step (11) for the repair procedure.
(1) We know that much of the Main Power Supply is working since many of the audio, video and digital processing sections appear to be working (sound, remote control, tuner, and video out).
(2) We know that the Backlight Inverter is working. Even thought the screen appears to be dark, light from the backlight tubes can clearly be observed. Further, even thought the screen is dark, you *can* observe a small amount of the backlight thru the screen.
(3) When working on LCD TVs and Monitors, the typical problem is backlight failure. (Fortunately this is NOT the case here.) Backlight failure is most often due to Backlight Inverter failure, or Main Power Supply failure. Rarely do the bulbs fail outright (although occasionally thru abuse a CCFL tube is cracked or shattered).
(4) The typical failure mechanism on LCD TV/Monitors that have many in-service hours on them is CCFL tube aging. As the CCFL tubes get older they require increasingly higher voltages to maintain the proper regulated current thru them which in turn creates the correct light output. The higher voltage is often beyond the design limit of the Backlight Inverter leading to component failure. Typically discharge breakdown arcing on the output transformers (that drive the CCFL lamps), or drive transistor failure in the Backlight Inverter power supply. Alternatively, the Main Power Supply may fail. Typically the Main Power Supply supplies +12V, or +15V, or a higher voltage (+24V?) to the Backlight Inverter subsystem. Once again, as the lamps age, more current is drawn, and if the Backlight Inverter doesn't fail outright, it draws excessive current from the Main Power Supply leading to either Main Power Supply failure. Alternatively, the Main Power Supply protects itself by shutting down once the excessive current is detected. This can often be seen as "monitor cycling" where by a LCD Monitor will initially power up, but subsequently cycles every few seconds as the Backlight Inverter draws too much current causing the Main Power Supply to shut down. Then, after a brief recovery period, the cycle repeats.
(5) Another failure mechanism, that should not be overlooked, is Electrolytic Capacitor failure. The Internet has many sites documenting either manufacturing defects in Electrolytic Capacitors used in any of the subsystems (Backlight Inverter, Main Power Supply, Digital Signal Processor, etc.). However, more often than not, Capacitor failure is due to component stress-due to the high ripple currents present in inadequately designed switching power supply subsystems. Additionally, many inferior Electrolytic Capacitors of Chinese origin are inadequately designed-they lack trace chemicals in the Electrolyte necessary to assure long service life.
(6) If you suspect any of the mechanisms described which cause an absence of CCFL backlight, you can often use a small pocket flashlight, and observe the screen image *is* in fact present on the LCD panel, but in the absence of sufficient backlight, you mistakenly believed the LCD panel to be dead.
(7) This is not the case here. We can clearly see that the CCFL backlight *is* lit, but we also do *not* observe any image on the LCD panel, even with an external flashlight.
(8) Thru this diagnosis of exclusion we assume that either the LCD panel itself is defective, or that the LCD panel is not receiving the correct drive signals from the Digital Signal Processor subsystem.
(9) A cursory examination reveals that the Digital Signal Processor board is producing output activity, which-even if malfunctioning-would likely produce some sort of LCD display activity.
(10) The LCD panel is totally dark (backlight is on, but no image at all). This failure is so absolute, it leads one to suspect power related problems as opposed to logic or drive problems.
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As Gopakumar Gopalan suggested, I checked for loose connections. Although I didn't find any, I removed the dust on the inverter board. It then worked perfectly for 2 days. Today, when I tried starting it again, the same problem recurred. What might be done now?
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