pls help me/.... lg 21fb5rb no display only sound

[dilan silva]

hi experts

i have lg 21fb5rb which when i power on, sounds comming with no any fault but black screen..

after 10 min all are going ok..

everytime i power on the tv.. black display sounds ok... after 10 min all are ok

first.. i clean all boards & main board

after i resolder all boards

but still same

pls help me to solve this

 

[dilan silva]

no one comes to help me?

 

[dilan silva]

what a bad site is this... no one comes to help

 

[KJ6EAD]

Had you titled your post something like "TV - No Display" you might have had a better result. Maybe if you delete all your ungracious insults and try again you still have a chance.

I'm curious and these questions are not meant to be rhetorical or inflammatory. I'm interested in the psychology behind some of the atypical behavior on the forum. What level of service did you expect from a purely volunteer community? What do you suppose motivates people to help? What result do you expect your comments to achieve?

 

[DJ.]

Hello,

I still have not understood your problem.

But I think these link can help you out.

**broken link removed**

 

[Rbeckett]

Mr Silva,
It is a good thing I am not a mod on this forum. Youre attitude and lack of patience would get you banned from my home site. Perhaps you could describe your issue a little more clearly and take the time to use punctuation and 1/2 decent sentence structure and you migh get some answers. As it stands nobody can help even if they really wanted to because your explanation of the issue is so vague. So to fix the problem, look in the lower left hand corner of the box and click on the triangle shaped icon near the corner and go from their.
WCB

 

[MrAl]

Hi,

Leave it turned on all the time, dont turn it off ever again


Sounds like the power supply for the backlight is not operating correctly. Dont have any other info right now however, sorry.
Try to get a schematic for it.

 

[dilan silva]

this is lg flatron tv,,, couldnt find schematic 21fb5rb

what will reason for this? i replaced nic connector ... but still same.. is there jungle ic fault.. (lg631 9r)


* thank you verymuch for reply...

 

[MrAl]

this is lg flatron tv,,, couldnt find schematic 21fb5rb

what will reason for this? i replaced nic connector ... but still same.. is there jungle ic fault.. (lg631 9r)


* thank you verymuch for reply...

Hi,

You're welcome. I think if you show a little patience you'll get more help with this too. Unfortunately this kind of problem like many other problems isnt especially simple to repair unless you can find someone that has experience with that exact TV set or one just like it. If you did find a schematic, we'd have to take measurements and see what is what, or what isnt what it is supposed to be.

Since it sounds like the backlight, maybe you could shine a light behind it with the cover off just to see if you can light up the screen from behind and see a picture during that first 10 minutes after turn on. If the light shows you a picture that way, then it is definitely the backlight and that narrows it down a little. As far as what part it is, that would take more effort.

Also, you said you turn it on and 10 minutes later it works fine but it takes 10 minutes to work properly. What happens if you turn it off for say 1 second only and then turn it back on, does it still work or does it still take another 10 minutes to work properly again?

I'll ask around about the backlight repair and see if anyone has any more info. Hopefully that's all it is.

 

[picbits]

I have had lots of LCD monitors and LCD televisions which have exhibited similar behaviour. Most of the time though its the other way around - they work for the first ten minutes then the backlight turns off.

Most have been cured by replacing the electrolytic capacitors in the power supplies. Quite often (but not always) they bulge at the top when they are bad.

 

[dilan silva]

sir this is not lcd or led ... this just crt colour tv..

here is look

**broken link removed**

 

[MrAl]

Hi,

Wow, unless you have experience working on high voltage supplies i dont recommend you trying to fix this. The anode has very high voltage on it and im not talking 200 or 300 volts, but 20000 volts or even higher. It's very dangerous not something to fool around with. You have to know how to discharge it before working on it or you might not be around the next day to fix it anyway.

That said, this is really a tricky problem where you probably need a schematic unless you can spot something burnt on the circuit board.
There's a slow start circuit in there somewhere but if the cap went bad...oh wait a minute...if the cap went bad it might be trying to start up during the first 10 minutes but not successfully because it may be trying to start too fast and the over current sense circuit turns the high voltage off thinking there is an over current. Eventually it builds up enough charge to allow it to start more quickly so the over current sense doesnt trip. Still, you'd have to locate this cap *if* that's what it really was to begin with. That's a bg *if* too as i dont have the thing right in front of me.

Did you have this thing apart yet? (not that i recommend it though unless you have a lot of experience with this stuff).

I dumped all my CRT's because the LCD's that replace them take up MUCH less room and use less power. Prices have come down a lot too in recent years...maybe time to think about a new LCD (LED backlight of course).

 

[tunedwolf]

12v & 5v Regulators and Decoupling Caps are known to cause these kinds of problems.