Question about LG 42LD520 42 in. HD-Ready LCD TV
I have an LG 42LD520 LCD TV. Over the last few months, it was clicking off and on. It's now permanently off. I opened it up. The capacitors are not swollen. I'm thinking about replacing the power supply. Is that the right fix?
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Posted on Jan 02, 2017
replacing the 10V caps with 25V caps is perfectly fine. In fact, if it was manufactured like that, those caps may not have blown.
Replacing a 680uF with a 1000uF could be problematic depending on it's function.
680uF is pretty specific when 500uF and 1000uF are much more common and therefore cheaper - one would think that the engineers would have tried using those in the design rather than a 680uF - makes me think the value of the cap is important to the frequency of the circuit it's in.
Other concerns might be whether he got any of them in backwards or not.
That's a rookie mistake, but still an easy enough one to make (for a rookie).
Also, with that many swollen caps, I wonder if there were any that leaked out the bottom before swelling at the top (IE - if some caps were missed in the replacement procedure)
Also, with that large a number of caps gone, other components may have been compromised or blown.
I'd be testing the transistors around those caps (most likely punched through rather than open), looking for fusible links (surface mount fuses, 0 OHM resistors) that may have opened up etc.
The initial attack on the problem was basically correct, and in many cases probably would have fixed it (if say the 680uF cap was functioning as a ripple filter).
But when that didn't fix it, a deeper analysis should have been done to complete the repair (including locating a 680uF cap).
Posted on Feb 27, 2011
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The issue you describe is consistent with a power supply board issue. This is the board where the AC goes to. This problem may have occurred as a result of irregular power supply, or excess power supply or power surge.
The TV is receiving current but cannot circulate or transfer the current to other necessary part of the TV because of the defective power supply board. You might be lucky it's just a blow fuse. Also a defective transformer can cause your TV not to power on.
All these can be checked on the power supply board.
But more often bad capacitors causes problem on the power supply board. I do not think the power board needs replacement, rather those defective capacitors is causing this issue. Open unit up and take a look at the power supply board.You will probably see one or more electrolytic filter capacitors that are bulged up in the top-not perfectly flat like the others.
The value of these capacitors will be different, most likely they will be somewhere around-820 to 2200uF/25 V( or /10V sometimes)
You can replace them with same values but I would recommend the voltage rating to be higher(like 35V for an original 25V) for reliability purposes.
What happens is,these bulged top capacitors will cause a low and unfiltered DC voltage=main board will malfunction(the relay will keep clicking until the caps are holding enough charge to bring the voltage up over a threshold point).
You can buy these capacitors at any Fry's or Radioshack store or you can order them online at vendors like "mcmelectronics.com"(look for electrolytic capacitors). After replacing these capacitor(capacitors) most likely the normal operation will be restored. Or you can by a refurbished complete power board to save you some stress.
Note: There may be also some other causes for this symptom ,like a defective T con board ,or main board,but the bulged top capacitors are the most common cause for this issue.
If you don't know about TV repairers, take the TV to the nearest repairman to fix the fault for you. Also, note that TV stores a lot of current, so wait a while before opening the TV back cover.
I hope this helps.
Posted on Jan 12, 2012
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