Question about LG 42LC2D 42 in. LCD HDTV

2 Answers

I have a toshoba lcd tv mod 42rv535u that has no back light. I ck the power supply and all voltage is good. I also put in a new inverter still no light.The set will come on and i get snd but no pix. if i put a light on the screen i can see a pix. Any help?

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  • patmac2 May 04, 2010

    Could i have a bad power supply? I did ck all voltages but a couple of heatsinks was cool.

  • patmac2 May 06, 2010

    That sounded like a good answer and thank you.
    Pat

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Http://www.scribd.com/doc/22277758/Toshiba-TV-LCD-Training-32wl36p

http://www.retrevo.com/support/Toshiba-42RV535U-TVs-manual/id/22963ag211/t/2/
http://www.service-manual.net/ashop/catalogue.php?cat=244&exp=&resultpage=48&shop=1

Hi at the very TOP, above find a Training & Service Manual This will give you great assistance. next is a user manual, a must have, and under that is a pay for Service manual, a MUST have .
Now with your "Backlight" problem. Think of a backlight, as really just a Lamp, it only has two connections, a bit like a Fluorescent tube, the "Inveter" simply steps up the voltage, from what is supplied to the "Input" to a much, higher voltage to run the "Lamp" You are going to have to find out, what that Voltage is, see if it is correct, as i wonder if indeed it is even there? If it is, you need to measure the Output of the "Inverter" with a High Voltage Probe/meter,and see what it's putting out, you see, even though, you replaced that, Inverter, perhaps the "Fault" destroyed it as soon as power was applied? You need to check, you absolutely need a Service manual for your exact unit, I could only find pay for ones, but you MUST get one, you simply cannot, repair this unit without, as you also must after repair use the service menu to restore defaults and setting again.
IF you wish to try to fix it yourself, and I do not recommend it without a service manual, So,. FIRST, you Must get a service manual, then you need, equipment, an Oscilloscope is a MUST HAVE.(may possibly be done without, if NO alignment, or pattern observation, is required). Also a Multimeter, and soldering iron, a DE-soldering station, an anti-static wrist strap, (Any TV is extremely static sensitive). Now FIRST you must make sure the Power supply is 100% as if this is NOT then nothing else can be. Also there are safety considerations, any unit that can cause a Fire or Explosion, or both, needs to be attended to with the utmost care. As if it isn't done correctly, a catastrophe is indeed possible, Faulty sets can cause a fire, and a fire in the middle of the night, I believe is not good. And any person that has attended that set, will be held to account. Now with that understanding, I guess proceed if you wish.
Troubleshooting say if it is shutting down, after a certain amount of time, of working and then faulting, then it is most definitely a "Thermal" problem, the way we "Find" problems such as this is "Freeze Spray" you use this on each component that is suspected of being the "Culprit" and you will soon,find that errant component. Now also not every fault is a Capacitor, I see many, many people that think, that Capacitors are always the "Culprit" now while that may be true in a few cases, a faulty Electrolytic Cap, or ordinary, Cap goes faulty, this is only a SYMPTOM, something has damaged those caps causing them to "Fail". One MUST always find the root "Cause", otherwise if you just treat, the SYMPTOM, the "Cause" will just make the "Symptom" come back, in short order, as the prime cause still, hasn't been fixed., Now Capacitors hate AC ripple, or Over Voltage. Thats it. Oh.. and Heat, if these Capacitors, are too close to a Heat Source, then thats a prime cause of failure. Resistors, hardly ever go faulty,and if they do, it is generally obvious. However it doesn't hurt to check values with our Multimeter. Remember though resistors are made, with up to 20% tolerance from stated value, as such, are not too critical, unless in Timing circuits etc. Always check, the Values, of resistors, as with any other component, with the power OFF. Now Diodes especially "Zener Diode", are another thing to check, those and ordinary "Signal Diode" should always be suspect. next we have Transistors and IC's. The Transistors MUST ALL be checked to see if they have a good, "Junction" this is done, with our meter set to "Diode Test" and usually are about 0.6 to 0.7. With IC's you must check, voltage levels, or Logic Levels, going in and out, have a look at the circuit diagram, and it will tell you what they should be. It is a good idea to always measure the Power Supply voltages, see if a "Rail" is Low, that will be because some component has gone somewhat or all short circuit, to Earth, now, if the "Rail" is Higher, suspect an "Open Circuit" component, like a Diode, or Transistor. The voltages expressed in the manual are spot on, ANY variation MUST be investigated. I have been doing all this for over 30 years now, and I do indeed wish, we could have a set of "Symptoms" and be ables to say.. "Oh that;s the so-in-so and replace this" however unfortunately this although does happen, most "Symptoms" can have literally tens, of "Causes" all often "Interlinked" One simply has to do a methodical troubleshooting procedure, and always think, "are my Voltages Correct" as this is how, you Fix the problem, by making them so. Keep up the good work. If that link above doesn't furnish a Service manual, it is imperative you get one, even if you must pay for it. It will pay for itself in about 2 mins. Now just replacing boards will most likely just end up with more faulty, boards, as related you MUST ensure that you have the cause of the event, before we change anything. I have seen so called, "Techs" replace every board, and virtually every component, and that STILL didn't fix it, because the "Fault, or Cause" lay elsewhere, and had not be repaired FIRST, you see that FIRST STEP, like everything in life, is, CRITICAL. So the very first readings you need to make are on the Power Supply, check each and every voltage, and work out from there, but now you have your user manual, it should be easy... just follow the troubleshooting steps within.
Now if you feel that it you do not want to do it. It is my professional advice is to get you set looked at by a Toshiba Authorised Service Centre, and ask for free "Quote", this way, you will be able to make an informed judgment, as to repair or replace. As these days seemingly insignificant SYMPTOMS, often cost as much to repair as it may cost to buy.

Posted on May 05, 2010

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  • Master
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Hi


Thanks for using FixYa. From what you have described it seems that the issue is with backlight as you have already replaced the inverter. It could also be due to the inverter circuits for the backlights. If circuits are fine then the inverter board is required to be replaced. All this is only recommended if you have some kind of expertise for checking the internal circuitry of the TV as these units have high voltages running even when the set is in off position. The cost to change the inverter board including labor would be around $250, if you get this done by a professional. Please do accept the solution if the issue is resolved or post a comment for further assistance.


Thanks
Rylee

Posted on May 04, 2010

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ajin_g_8.jpg ok

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2 Answers

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