Weird 29" LG Flatron Problem

[GraphicMan]

Hello guys

to cut a long story short
I got a used 29" LG crt tv but in mint condition
it worked fine with a great picture for 7 month

then it started to shut down by itself few times a day
to power it on again I have to press the power button on the TV to off then wait few sec then back on and it works

it stayed like that for about 10 days

then one day I turned the receiver off as the usual the tv display "s-video" on a black screen then after 10min it goes to sleep mode
but this time I was surprised with a loud electric shock sounds before it went to sleep when I turned my head to see the screen it was displaying some mixed colors and it went off, I also smelled some mild electronic burn smell

I thought the tv failed completely this time but I was surprised that it did turn on but producing same very loud electric shock like sound, so i turned it off immediately

when I opened it up I found the main biggest cap have a belly on top
so I replaced it with exact number but the problem is the same

can some1 tell me what is that? and is it fixable?

Thanks

[petehall347]

Re: Weird 29" LG Flatron Problem

most things are fixable .. post some nice pictures of all the parts .

[R_J]

Re: Weird 29" LG Flatron Problem

I tried looking for information on "weird 29" and found nothing. Maybe you should try posting the model number at least?? and don't forget the pictures.
And that large cap's plastic top can "dome" but the cap will usually be fine.

[GraphicMan]

Re: Weird 29" LG Flatron Problem

Sorry I forgot to post the photos
here it is
including the model #

but what about that electric shock very high noise?does not say anything?
also the sequence in which the case happened?

I would really like to fix it, the TV set has a very good bright picture, so I am assuming it is has not been used that much

and yes I think the cap was not the prob at all
but I changed it because many said a domed cap + turning off by itself means a bad cap

[dick_barton]

Re: Weird 29" LG Flatron Problem

Can you check out how close the schematic is to your set. The power supply may be similar. See page 34

The set is so dusty it's difficult to see any components markings. Also if brushed out you may see where the electrical smell / burning was coming from.

[R_J]

Re: Weird 29" LG Flatron Problem

I would check the board for poor solder connections, Check the connections on the high voltage transformer and any parts mounted to heatsinks
Caps I would check/replace would be C809, C810, they fail often on other similar tv's

[vinceroger69]

Re: Weird 29" LG Flatron Problem

The loud electric shock noise you hear could be cracked casing/dampness etc on the line out put transformer or the lead from the transformer to the crt arcing out somewhere just be really careful as very high voltage when working on crt tvs even if been unplugged a few days you can still get a nasty shock been there done that got scar too prove it.

[GraphicMan]

Re: Weird 29" LG Flatron Problem

Thank you all for your prompt reply's

I am not an electric engineer, just general knowledge

I was hoping to know if that defect is something known or popular

but it is logic for me to know that 10 days of auto shut down is something that lead to that end?

it looks like i has to be checked out by a professional?

[petehall347]

Re: Weird 29" LG Flatron Problem

most times i had faults with crt tv.s it was the H.O.T transistor or flyback transformer . or a diode .

[GraphicMan]

Re: Weird 29" LG Flatron Problem

most times i had faults with crt tv.s it was the H.O.T transistor or flyback transformer . or a diode .

Thanks bro
is that something easy to replace or must use the same part from a similar model?

btw, since the screen produce random mixed colors, would replacing the WHOLE chassis with an exact one from another set fix this problem?

[vinceroger69]

Re: Weird 29" LG Flatron Problem

swapping the chassis should solve the issues as long as the replacement is working ok.

[GraphicMan]

Re: Weird 29" LG Flatron Problem

swapping the chassis should solve the issues as long as the replacement is working ok.

Thanks Vince

[vinceroger69]

Re: Weird 29" LG Flatron Problem

just be careful high voltage could be stored when removing the anode cap from the tube have a read up on how too discharge them as it gives a nasty shock.

[GraphicMan]

Re: Weird 29" LG Flatron Problem

just be careful high voltage could be stored when removing the anode cap from the tube have a read up on how too discharge them as it gives a nasty shock.

yes I know that, 20K+
however I have read in an article that that was in the past, all modern CRT TV have a resistor to absorb that stored energy when you turn it off

http://lowendmac.com/2007/the-truth-...-shock-danger/

anyways I dont think I will do that anyways, it is beyond my experience

I am still surprised that nobody have witness this failure type before!!

[angelos]

Re: Weird 29" LG Flatron Problem

The arcing of EHT can definitely cause your TV to go into standby or even shut down. I bet there is a crack around the LOPT chimney or on the red EHT wire going to tube.
Getting another LOPT will be difficult but depending where the EHT leak is you might be able to insulate it with some kind of sealant. The best thing is to catch it in the act when it arcs. Just keep your body parts far away when running set.

Regards

[GraphicMan]

Re: Weird 29" LG Flatron Problem

The arcing of EHT can definitely cause your TV to go into standby or even shut down. I bet there is a crack around the LOPT chimney or on the red EHT wire going to tube.
Getting another LOPT will be difficult but depending where the EHT leak is you might be able to insulate it with some kind of sealant. The best thing is to catch it in the act when it arcs. Just keep your body parts far away when running set.

Regards

Bro can you please share some pics for the parts you want me to check?
I will then make some photos for my TV for the same parts and see if this is realty the problem

thank you

[R_J]

Re: Weird 29" LG Flatron Problem

You say it is making a very loud electric shock like sound where is the sound coming from? Is it coming from the high voltage transformer?
Is it a high pitched squealing sound or is it a loud snap... snap type sound?

If it is high voltage that is arcing, check it in a darken room, you should be able to see the arcing.

[GraphicMan]

Re: Weird 29" LG Flatron Problem

You say it is making a very loud electric shock like sound where is the sound coming from? Is it coming from the high voltage transformer?
Is it a high pitched squealing sound or is it a loud snap... snap type sound?

If it is high voltage that is arcing, check it in a darken room, you should be able to see the arcing.

It is hard to know where the sound is coming from because it is very loud and I shut down the tv quickly because it seem so wrong

it is not high pitched sound, I will try to video record that the next time
I have not tried to turn it on with its cover open, but from many of the replies it seems like I have to remove all the inside dust first in order to see if there is any cracks around any component and to check for poor old solders as well
if I did not see anything that seem wrong I will then turn it on and see if there is any visible arcing!
I have not done anything like this before, I am also sure that this set have never been opened or serviced before

[GraphicMan]

Re: Weird 29" LG Flatron Problem

I think it is clear now
I have already recorded a video but for ease i am uploading this screenshots of it

the sound is much less without the cover, seems like the cover was scaling it a lot

the arcing is coming out from the flyback transformer as few members said (many thanks to them)

I have also uploaded a clear pic for it, I cant see any cracks, it look so new!

what do you think guys?!

[petehall347]

Re: Weird 29" LG Flatron Problem

that is cracked or lost its insulation .. new fly-back will likely be expensive if you can even find one .. i used to scrap sets with bad fly-back transformers as they simply wasn't worth spending that sort of money on .
you may get lucky and find a new one cheap enough .