LG LCD TV image freeze \ won't start

[yrn11]

Hi all,

Recently my LG 32' LCD TV is doing a bit of problems, it started by during run time the image is freezes and then continued to it won't start at all, the red led below is blinking and it won't start.

at first I thought it was due to bad caps (as read online), but they seemed fine and yet I've replaced them other theory was related to soldering disconnection in the main board due to many heat \ cold occasions.

for conclusion the issue still remains after trying to bake the main board and replacing caps.
it seems like after disconnection the board from power does the trick.

any idea what could be the issue?

 

[bigdogguru]

for conclusion the issue still remains after trying to bake the main board and replacing caps.
it seems like after disconnection the board from power does the trick,

any idea what could be the issue?

Could you elaborate on your statement above, exactly to what "trick" are you referring?



BigDog

 

[yrn11]

Could you elaborate on your statement above, exactly to what "trick" are you referring?

Hi, unplugging it from the power input.
after each time I've disconnected the boards it worked for a day, on the next day it started doing problems again.

 

[bigdogguru]

unplugging it from the power input.
after each time I've disconnected the boards it worked for a day, on the next day it started doing problems again.

The issue could certainly be a bad connection due to thermal expansion or possibly a power supply issue.

You seem to suggest that you've already replaced the caps on the power supply boards, is that correct?

Do any of the boards which you disconnect from the power supply contain BGA package devices?

As you mentioned, "baking" a board is often the homebrew remedy for thermal expansion connection issues, however it is far from a perfect remedy and could certainly be the cause of additional issues to arise.

Heating a board up to a temperature to permit solder reflow is a particularly delicate procedure, maximum time intervals must be observed, so as to not damage other components on the board. It's particularly difficult to successfully reflow a BGA package device's solder balls, which may require specialized equipment to target only the BGA package device itself.

Typically, faulty display driver boards manifest their symptoms visually on the screen when powered up, irregular lines, numerous stuck pixels, waviness of the picture, etc.

Replacing the entire suspect board, particularly if the board has BGA package devices maybe the only sure remedy.

However, that being said, if the entire system powers down, particularly after being powered up for a period of time and there is a lack of visual irregularities mentioned above, such symptoms often indicate an issue with one of the power supply boards, it could be a bad connection or a faulty component which is thermally sensitive.




BigDog

 

[yrn11]

You seem to suggest that you've already replaced the caps on the power supply boards, is that correct?

Do any of the boards which you disconnect from the power supply contain BGA package devices?

Typically, faulty display driver boards manifest their symptoms visually on the screen when powered up, irregular lines, numerous stuck pixels, waviness of the picture, etc.

However, that being said, if the entire system powers down, particularly after being powered up for a period of time and there is a lack of visual irregularities mentioned above, such symptoms often indicate an issue with one of the power supply boards, it could be a bad connection or a faulty component which is thermally sensitive.

BigDog

I did replaced the capacitor and it didn't helped very much, when I refer to the issue I mean by that the image is freezed with irregular lines across the screen, at that point shutting it down and trying to boot it back up won't succeed.

There is a BGA package I will now upload pics of the boards.

 

[dougmc]

I would use freeze mist comes in a spray can. When it the problem starts spay the ics. testing for bad connections I use a heavy duty fiberglass rod. Tractor supply has them Zareba 60 in. Fiberglass Rod Post..I cut it down to 12" and round the ends a little.Strong enough to flex the board and enough weight for tapping on the boards for connections.

 

[yrn11]

I'm not sure freeze mist would do the trick here.
I was able to reproduce it quite easy, I opened up the back part of it and turned it on, waited about an hour and then turned it off.
once I tried to turn it on it, the LCD light doesn't come on, it start the power on procedure (raise up noise) and then it goes ahead and lower it's voltage (noise is decreasing).
After letting the TV to be powered off for couple of sec and trying to power it on again it works ok.

to summarize -
It seems like it struggling to boot on once issue occur, I've tried during run time to tap on the boards to see if a bad connections is causing the issue but nothing happened.


any ideas?

 

[pradeep.g.belchada]

their is a problem in smps section

 

[D.A.(Tony)Stewart]

The blinking LED fault code is your clue, most likely one of the SMPS.

IF it detects over-current in the CCFL backlights, then the SMPS for those may be one possibility.

Does the display color look off-white in the corners?

If this all points towards expired CCFL tubes, I know TV parts stores and also DigiKey stock a wide range.