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LG TV 42LD420 not turning on

seagull62 Posted messages 41 Status Member -  
 Nanouche -

Hello everyone,

I come to ask for a little help from those who master electronics and who would like to assist a small electrician.

Here is my problem:

My LG TV 42LD420 won't turn on anymore; electricians like clear failures of this type, so I dismantle the device to try to detect something abnormal and, with a tester in hand, I head towards the power board and check the fuse just behind the power connector with an ohmmeter. Bingo, it starts off well since it is blown.

As a good electrician, I tell myself that if it blew, there is a reason and that I must find it, but I am not an electronics expert, and all these components on the board don't evoke much for me except for a visual inspection of the capacitors which seem fine (not swollen).

However, I notice that a "clash" occurred at what I believe to be two neighboring resistors (see the attached photos).

My question is as follows:

At this stage, what should I methodically do with these elements found?

Should I change the fuse and the burnt resistor(s)?

How can I know the respective characteristics of these components?

How to test the resistors?

Can all these observations alone explain the failure?

I hope for your feedback, thank you in advance.

Have a nice day.


 


13 answers

  1.
    Epiloguest Posted messages 219 Status Member 25
     

    Hello.

    What interests me is the other side of photo 3. We are on the component side; it’s the printed circuit side that I would like to see. This is probably the source of the malfunction.

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  2. seagull62 Posted messages 41 Status Member 5
     

    Hello Epilogest,

    here is the other side…

    thank you

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    1. Epiloguest Posted messages 219 Status Member 25
       

      Not easy to detect like this without a diagram and from a distance. The photos are nonetheless telling ;-)

      There might be a few fresh solder joints to make.

      The most important thing for now is these resistors; I think they should be around 10 ohms at a glance. Test R602 with the ohmmeter. If it's not broken, you should find this value. R601 is the same.

      Not sure that resistor R601 is out of order; the fuse may have blown first? It's possible that these are protection resistors? We could have confirmed this with a diagram of the television.

      For the fuse, use the same value, of course.

      The problem may come from elsewhere. Time will tell.

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  3. seagull62 Posted messages 41 Status Member 5
     

    Hello again,

    So, I took out my 15€ multimeter from about fifteen years ago, and no matter which range I choose, it shows 000 on each of the resistances.

    I tried the color code translator online for the first time, which returned 49 Ohms, but I'm really not sure about the colors :-( (see photo for comparison)

    Do you think I can already change these 3 components and see what happens?

    If so, how can I ensure the result I get, and where do you think I can order from?

    The fuse is a 250V / 5A but it's special….

    I've searched for the schematic of the board, but I can't find it :-(

    The board would be the LGP 42 10 LF1

    Thanks again for your help ;-)

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  4. Epiloguest Posted messages 219 Status Member 25
     

    I don't think it's yellow but rather gold.

    It's in the other direction :-) Brown = 1, Black = 0. After that, it should be the Tolerance if I remember correctly.

    For the universal controller, set it to the lowest position for a resistor of this value.

    250V / 5A, it's a solder fuse, it should be available.

    It doesn't cost much to change what's defective, the resistor and the fuse. However, the result is not certain. It's worth trying; there could be something else. If a protection resistor has overheated or is broken and the fuse followed, that is part of the device's safety. It doesn't blow for no reason.

    I was on a color calculator, it gives me: 0.1 Ohm and not 10. I correct that.

    I have been buying from Électronique 44 for a very long time.

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  6. Epiloguest Posted messages 219 Status Member 25
     

    Give me an enlarged photo of this part:

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  7. seagull62 Posted messages 41 Status Member 5
     

    Good evening,

    According to your instructions, I get this (indeed not the same value):

    Here is the requested zoom:

    Thank you and have a nice evening ;-)

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    1. Epiloguest Posted messages 219 Status Member 25
       

      Nothing to report on the soldering in this area.

      Behind all this, there may be another faulty electronic component, but it's worth attempting the repair: 2 resistors and 1 fuse. Do not attach the resistors to the printed circuit board, as they heat up; let them breathe.

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  8. seagull62 Posted messages 41 Status Member 5
     

    Good evening Epiloguest,

    I have desoldered the components in question, here they are:

    So we do indeed have 1 fuse 5A 250V and 2 resistors of 0.1 Ohm, I will of course get several in case there is something else....

    As I am lost since I don't know this field at all and can't find the exact match, here are products found on eBay, what do you think please?

    Resistor or even Resistor 2 and Fuse

    The links do not work, so I am including them in full:

    https://www.ebay.fr/itm/114239023341?hash=item1a992d28ed%3Ag%3AfssAAOSwWxlezpif&amdata=enc%3AAQAHAAAAoKLo26zXODxEV9rjontdmZIsUrW%2Bkvj3feYm6yxF5fBaQadlRGKMTNVHbsWkYW7TzXyeZv%2B094XRdtBFVfNOn%2F8Pf%2Fbx0sJfLE9IpMaXHN9IpamU%2FSF%2FrcbocCToy6D49yf%2BZ0rUBvioYjJ%2BgjXH5fCTdN6o7CNOVUOQtuqCgU8awv34XFR6J5dkQw9AQQ%2B8Cyq97A5bzbRNSDb8bke4dWQ%3D%7Ctkp%3ABk9SR6TD9NeUYQ

    https://www.ebay.fr/itm/184051948128?hash=item2ada59da60%3Ag%3AFb4AAOSwedNebfz2&amdata=enc%3AAQAHAAAA4Ab3aRCBROtFisZ1nLbO1kMi6bBSppBzuKOiAP5j7k9bXMalyiJA5nOm2WisY6L0BkbyGFOulczrzogyk4YM%2BKzR2qHo4iUYBL2szHIQR63yu8WirNK%2FrbU1OUv%2Bnfb4NJNRQdfExcLxBI2NoSH17S2tkhAIG4Y%2FTggRSexQkb5m24QRUICQSzx9MeEC1hAUy4MFBpc8qzVhEN6kGDRRY%2B%2FZ055eqMRgLWW2I8CtX9rIex1aktTdfWa%2F8EvHYSvhxnuqvZfnrLZR%2Bz0LQzphR41nKzop8heyDMRRLs7I0pKH%7Ctkp%3ABFBMnsP015Rh

    https://www.ebay.fr/itm/113949209117?chn=ps&norover=1&mkevt=1&mkrid=709-134431-41854-0&mkcid=2&mkscid=101&itemid=113949209117&targetid=1258872138203&device=c&mktype=pla&googleloc=9055843&poi=&campaignid=9567047449&mkgroupid=97621257825&rlsatarget=pla-1258872138203&abcId=1139516&merchantid=116026813&gclid=CjwKCAiApvebBhAvEiwAe7mHSAH1z5Fv1J-L372juR7M1ELNFHC8Cs_0gg45Sea9ZrzDt1_2oTuOQxoCMr0QAvD_BwE

    Thanks again and have a good evening????

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    1. Epiloguest Posted messages 219 Status Member 25
       

      Good evening seagull62.

      Considering your links.

      What is the length of a 0.1 Ohm resistor (without the leads) on your television? This is to determine the power in Watts before buying. Am I being picky?

      In your link 2, in its photo it looks like 470 Ohms.

      Have a good evening.

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  9. seagull62 Posted messages 41 Status Member 5
     

    Hello Epilogest,

    The length is 11 mm and, indeed, if we look at the color code in their photo, it shows 470 Ohm, but I think their photo is standard and that the characteristics are what counts.

    Thank you and have a good day;)

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    1. Epiloguest Posted messages 219 Status Member 25
       

      So it’s 1 Watt like in the text of your second link: Value: 0.1 Ohm and 1 W

      In your first photo, I noticed another fuse. Is it not blown as well?

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  10. seagull62 Posted messages 41 Status Member 5
     

    Good evening,

    The second fuse is okay, I am waiting for the ordered material and will report back ;-)

    Thank you

    See you soon…

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    1. Epiloguest Posted messages 219 Status Member 25
       

      Hello.

      If it jumps, it's because there's a short circuit and it won't be easy to detect.

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  11. seagull62 Posted messages 41 Status Member 5
     

    Hello,

    Let's stay positive ;-)

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  12. seagull62 Posted messages 41 Status Member 5
     

    Hello Epilogest,

    I received the equipment which I was able to install but with no result since a resistor burned out again (not the fuse)

    So here I am in a dead end wondering if I should change the power supply board, but where to find one and especially at what price :-(

    I find that the wires of the new 0.1ohm 1W resistor are much thinner than the original.

    What do you think please?

    Thank you and have a good evening :-)

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    1. Epiloguest Posted messages 219 Status Member 25
       

      Hello seagull62.

      It's the resistor that acted as a fuse. The legs of the resistor are fine even though they are thinner.

      I'll check if we can find this power supply board.

      How long have you had this television?

      It's a clear failure, generally it's easier to detect. With some basic knowledge in electronics, you could have tested a few components.

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  13. seagull62 Posted messages 41 Status Member 5
     

    Good evening Epiloguest,

    Yes, I agree with the outright failures, it's easier to approach, but you need to know a minimum and personally my only solution, unless I get help, is to change the board if I can find it and it's not too expensive;-)

    The television dates from November 2010

    The board references:

    Thank you again ;-)

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  14. Nanouche
     

    Hello.

    I have the same TV. I plugged in my Orange box to watch TV. At first it worked very well for about 3 days, and since then the TV turns on and off. When I unplug the HDMI, I perform the 30-second procedure. The TV turns on normally as soon as I replug the HDMI port. I turn on the box, it works for 2 minutes and the TV turns off and reboots with the LG logo; basically it turns back on and turns off and then nothing. Should I give up and buy another TV? This TV was given to me.

    Thanks to those who can help me

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