LCD TV turns off randomly

[silvergoat]

I've had this TV for about 5 years now and I'm about to open it up to see what I can find. I have not worked on TVs before so I'm not sure what the best way to make sure capacitors are discharged is. I'm hoping it's just a couple caps and not any other hardware because I'm not experienced enough to do much more than swap out parts. Testing on boards electronics is unlikely unless I have seen someone do it or have detailed instructions.

Off to open it up.

[silvergoat]

Re: LCD TV turns off randomly

These are the pictures I took.

I took a close up of the two biggest capacitors on the board. They look a tiny bit bulged. I'm not sure that it means that they are bad or if that's not how they're supposed to look, but all capacitors I usually see are completely flat from crease to crease. These are the first time I've seen caps this big so I'm not exactly sure. I also don't know how to make sure they are discharged so I'm not going to touch them just yet.

[richpart]

Re: LCD TV turns off randomly

Got a 32 inch with the same board configuration. Yellow light only. Still working with it. If I get lucky, I'll pass on the info. Caps in my supply are fine, I can tell you that much.

[silvergoat]

Re: LCD TV turns off randomly

Got a 32 inch with the same board configuration. Yellow light only. Still working with it. If I get lucky, I'll pass on the info. Caps in my supply are fine, I can tell you that much.

Thanks-

[multimeter]

Re: LCD TV turns off randomly

check the large caps with a multimeter to see if they have voltage on them,if they do ,just discharge them with a household light bulb, solder wires to it then just touch them on the big caps for a few seconds,no need to worry bout the smaller caps,sounds like you have a cold joint on the power board,have a check and retouch with new solder where they might look cracked

[selldoor]

Re: LCD TV turns off randomly

Hi - random offs are often hard to trace. How random are we talking and if you turn it back on does it come on straight away. What does the power led do when it goes off. Is the going off preceeded by screen flicker.
When turned on from cold does the screen look at all pink.
Does it still turn off as much with the back off - ie when cooler.

Your pictures are not really sharp enough for troubleshooting.
This is what I usually say on first time threads.
Welcome to the forum-
We can help a lot more if you please post good clear pictures of the whole chassis, and then pictures of each board, front and back and close up of connectors, (max resolution 2000x2000 and 2MB) using the manage attachments button, which is found by clicking "go advanced" under quick reply.

Please do not post inline and offsite as they slow down the loading of pages.

Examples of what is needed
https://www.badcaps.net/forum/attach...1&d=1290283049

https://www.badcaps.net/forum/attach...7&d=1280167246

It will be useful if you can say what the supposed fault was and a bit about yourself - skills tools etc.

Have you got a multimeter and soldering equipment and can you use them.
If you make the point that you are totally new to electronic repairs, as I think you have indicated, members will take this on board and advise every step of the way and when you are working on high voltages will usually remind extra care.
Please update your profile with where you live and mains voltage.

[richpart]

Re: LCD TV turns off randomly

Got mine apart on the bench right now. Of course it's worse than yours, won't even come on.

Main Board:

So far I have found 4 bad surface mount caps located just left of the tuner near a regulator and a crystal. There are (2) 2.2uf and (2) 10uf at 50V each (Surface Mount) Aluminum Electrolytics that my Blue ESR meter is reading at between 11 and 13 on each. Very bad caps right off the bat. I'm still working with it because I suspect there are more to be found.

[richpart]

Re: LCD TV turns off randomly

I'm also finding several 100uf 50V surface mounts in various places on the board that are reading an esr above 1 whereas my new caps read between .3 and .4 respectively. So far, the main board caps have not aged gracefully lol.

[silvergoat]

Re: LCD TV turns off randomly

I talked to my brother and he described the problem for me-

He said when you'd turn it on, the screen would be black, and you'd have to turn it off and turn it back on again to get it to turn on. My buddy has the same exact TV and he is having the random shut offs- on his TV and the screen does not come back on for 10 minutes or so. I don't have his TV yet, but I asked to bring it to me in case I have to order parts, I can do all at once and save myself a couple bucks.

I don't have a digital camera, but I'll see if I can borrow one to snap better pictures.

I have a multimeter that I don't know how to use, and a soldering station that I've been practicing with for a few months.

There are three boards on mine, I've noticed that richpart has described a main board and a power board- which is which, and what is the third board?

[richpart]

Re: LCD TV turns off randomly

That's my conclusion on these gentleman. The main board surface mount caps are deteriorating and as they get worse, the set becomes more stubborn to turn on until finally it gives up the ghost. If you are not comfortable replacing surface mounts, looks like you'll have to buy the main board. The board also has them mounted on the bottom side as well.

[silvergoat]

Re: LCD TV turns off randomly

I should be able to replace the caps- I need the practice anyways because I need to get more familiar with my soldering equipment. For example, I just learned that to desolder the board, the temp has to be dang hot- I set mine to almost 700F and the solder still took a number of seconds before it began to melt. Resoldering was as easy as it's ever been, though. I'm not sure if it's the big joints that is making it easy to clean up the hole, or if the flux pen I used really helped, but so far this is a lot easier than desoldering and resoldering motherboards where it seems the solder doesn't really like to flow to where it is needed.

[richpart]

Re: LCD TV turns off randomly

The set I have belongs to a friend that gave up on it a long time ago. I'll fix it and surprise him when I give it back working.

[vinceroger69]

Re: LCD TV turns off randomly

this seems a good soldering guide silvergoat
http://www.infidigm.net/articles/solder/#desoldering

[silvergoat]

Re: LCD TV turns off randomly

The set I have belongs to a friend that gave up on it a long time ago. I'll fix it and surprise him when I give it back working.

same here- this one is going to replace the TV that was stolen out of my buddies garage. It was yet another of the same TV model- I hope it's going bad so the thieves get minimal use from the TV.

[silvergoat]

Re: LCD TV turns off randomly

this seems a good soldering guide silvergoat
http://www.infidigm.net/articles/solder/#desoldering

I've read and watched a lot of soldering guides....thankfully, I haven't had to replace any of the smaller items illustrated in that link. Maybe later, but I don't even know how to diagnose problems on circuit boards. I would benefit from learning some basic electronics for sure.

[selldoor]

Re: LCD TV turns off randomly

I talked to my brother and he described the problem for me-
He said when you'd turn it on, the screen would be black, and you'd have to turn it off and turn it back on again to get it to turn on.

You are beginning to confuse me here? Does you brother have a set exactly the same?

We need to know what YOUR set does

My buddy has the same exact TV and he is having the random shut offs- on his TV and the screen does not come back on for 10 minutes or so. I don't have his TV yet, but I asked to bring it to me in case I have to order parts, I can do all at once and save myself a couple bucks.

It will get too complicated if you start trying to troubleshoot/fix two /three sets
at the same time in the same thread. (For us- if not you)


I don't have a digital camera, but I'll see if I can borrow one to snap better pictures.

I have a multimeter that I don't know how to use,

Do you have instructions? if not can you download them or state the make/model number - a picture of it would help. When you have fathomed it - practice on baterries power supplies fuses- anything electrical even mains (WITH CARE) practice holding the probes and watching the screen.

and a soldering station that I've been practicing with for a few months.

There are three boards on mine, I've noticed that richpart has described a main board and a power board- which is which, and what is the third board?

The Power Board is the one with the BIG caps on
The Main or Video board will have the Tuner on it - a large silver metal can where the aerial /cable plugs in.

Third board ???? (Pictures are everything you see)

Could be a separate inverter board, could be a power supply filter board,
could be a Tcon board? - We will know when we see it

In your next post state in capitals the make and model number of the set
and chassis number if you can find it.

[selldoor]

Re: LCD TV turns off randomly

Sorry for double post- De soldering -try adding some fresh leaded solder to the
joint you are desoldering - it seems to help it melt at a lower temp 700deg sounds
hellish hot 400deg should do it otherwise you may cause some damage.. Another trick is to pre heat the area for larger joints with a hair dryer.

[richpart]

Re: LCD TV turns off randomly

List of all bad caps on the main board:

Top tuner side:
2911
2912
2024
2921
2061
2355
2396
2356
2561
2380
2262
2843
2837
2834

Botom Side:

All on attached plug in card and

2910
2311
2308
2526
2254

[richpart]

Re: LCD TV turns off randomly

You will see that I'm using regular capacitors topside because I don't have enough surface mount to go round. This is my preference.

[selldoor]

Re: LCD TV turns off randomly

[Quote selldoor]Third board ???? (Pictures are everything you see)

Could be a separate inverter board, could be a power supply filter board,
could be a Tcon board? - We will know when we see it [/Quote]

Haha - sorry you have a pic and the best one at that. It is none of the
above it is an audio standby card No 3104 328 41725 ( whatever that is!!) I have not come across one before.