LG 42LC7D Black Screen (No display)

[kilooonl]

So I got given an LG 42LC7D 42" HD TV.

The issue with it is that when you turn it on, the green LED blinks 8 times before remaining solid.
After which, the screen remains black. Just black. However the back light works as you can see the streaks of light.

Before it was given to me it would take about 5 minutes to "warm up" (display picture), after some time it stopped warming up and that is when it began doing what it is now which led me to believe capacitors.

So I pulled the TV apart to find 5 bad capacitors on the power board, replaced them... and still, black display. Fuses appear OK by the way.

I've been trying to find a solution or viable fix for this for days. A lot of people seem to just replace the caps and it works fine afterwards.
There are a few more caps which aren't showing visible damage or the end of their life, which I have now replaced (as well as the other 5), to no avail still...

I have no idea what to do now. Keep in mind I have a good knowledge with technology & electronics and am a fast learner, the TV repair game is new to me however.

[tom66]

Re: LG 42LC7D Black Screen (No display)

Can you post some images of the parts in your set?

Where did you buy replacement capacitors from? If you bought them from a place with "Radio" and "Shack" in the name, they will definitely be unsuitable for purpose.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

Can you post some images of the parts in your set?

Where did you buy replacement capacitors from? If you bought them from a place with "Radio" and "Shack" in the name, they will definitely be unsuitable for purpose.

Hey mate, I will do.

Haha no Radio Shack in Australia, I buy them from an electronics dealer I do work for on occasion, JayCar Electronics.

[tom66]

Re: LG 42LC7D Black Screen (No display)

JayCar aren't much better... not sure if they sell decent ones... best to replace them with digikey/farnell sourced Panasonic or Rubycon caps.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

Here's some pics.


Although it may not look like it, on the picture showing the TV on, the back light is visible on the entire TV, not just the bottom half. My camera is horrible :P Also on the pink cable where it shows a mark, that is heat shrink where I stripped it and re-soldered it as it looked like it was damaged/cut beforehand, so I re-soldered and used heat shrink to fix it just in case.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

JayCar aren't much better... not sure if they sell decent ones... best to replace them with digikey/farnell sourced Panasonic or Rubycon caps.

The guy I go to is a sub-business of JayCar (only orders some stock from JayCar), he orders caps elsewhere from another guy. He said they'll be good for what I want them for. He also ordered caps with a 10v increase (eg, replaced 25v with 35v) for me.

[tom66]

Re: LG 42LC7D Black Screen (No display)

The capacitors you have used are not suitable. You need to replace them with the correct type (low impedance, high ripple current, good quality) to get a base-line to work from.

If you can order from element14, they stock Panasonic and Rubycon capacitors.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

I'm using Jamicon 105°C electrolytic capacitors... what's wrong with them?

[tom66]

Re: LG 42LC7D Black Screen (No display)

They are poor quality and 99% are not low impedance which means most power supplies will have problems with them. Cannot be sure if bought from retail shops, they don't sell low impedance/low ESR caps. 105C means very little here, that is only related to lifespan.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

They are poor quality and 99% are not low impedance which means most power supplies will have problems with them. Cannot be sure if bought from retail shops, they don't sell low impedance/low ESR caps. 105C means very little here, that is only related to lifespan.

hmmm, I understand your point but why wouldn't I see any change whatsoever after replacing bulged caps with these, at least momentarily at the least? Not trying to hassle you, just trying to understand a little better, and am kinda broke right now so wondered if there is anything else I can do to find out what may be causing this issue besides caps, if it isn't caps.

[tom66]

Re: LG 42LC7D Black Screen (No display)

The problem is you can't be sure. You could be chasing a wild goose. We have had a few TVs and monitors here which the owner has used generic caps in. They didn't work, not even once. Then they put good caps in and they work. You can try testing the power supply outputs, as poor/bad caps generally cause low output voltages.

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

The problem is you can't be sure. You could be chasing a wild goose. We have had a few TVs and monitors here which the owner has used generic caps in. They didn't work, not even once. Then they put good caps in and they work. You can try testing the power supply outputs, as poor/bad caps generally cause low output voltages.

Alright, I'll do that, and get back to you. Thanks mate

[willyam1]

Re: LG 42LC7D Black Screen (No display)

hi.
if your backlight is working after replacing the bad capi and you have no osd no data in the screen most of the time this is a case of a eeprom in the main board in the bottom of the board 24c32 SMD .
YOU CAN REPLACE A BLANK ONE SHULD BE WORKING GOODLUCK.
WILLYAM

[kilooonl]

Re: LG 42LC7D Black Screen (No display)

Just an update. On the main board there is a green button, if I press it while the TV is on, pink & red diagonal lines flash on the screen and then flash off, and the speakers make a noise too... is this of any help?

[budm]

Re: LG 42LC7D Black Screen (No display)

How are the voltages on the T-CON board?