LG 43UF7709 - Blinking Screen, No Picture, No Sound

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I baked with 200 degree Celsius for 10mins. Its get hot, but when is it very hot? I have a multimeter with temperature function. So is there a range of temperature where we can say xd engine is dead?

[diif]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Hi Everyone, i will presend my Result:

Yesterday i first try to "reflow" the ic in my oven. 1 IC i think is succesfully reflowed. But nothing changed.
Then i realise that blinking LED LD701 starts to blink later than normal. So i touched several Parts and see the engine getting very hot. So i tried today a second baking, this time on the engine. It dont helped out.

Now i know who is the bad guy! Its LD XD Engine LGE7411

My Project will wait, till i buy a hot air gun (or should i buy a rework station?). After i get a hot air gun i will take of the engine and look how its under it. I never done a reballing, but there is for everyone a first time right? Will update this theard if i take it appart!

Special thanks for helping me out to:
nomoresonys
budm
diff

What temperature did you bake at ? If you were reading shorts and it's getting very hot, it's probably dead.
I'd forget reballing and go with a replacement XD engine.

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Reballing with a stencil: https://www.youtube.com/watch?v=vplUa0PByGw

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Hi Everyone, i will presend my Result:

Yesterday i first try to "reflow" the ic in my oven. 1 IC i think is succesfully reflowed. But nothing changed.
Then i realise that blinking LED LD701 starts to blink later than normal. So i touched several Parts and see the engine getting very hot. So i tried today a second baking, this time on the engine. It dont helped out.

Now i know who is the bad guy! Its LD XD Engine LGE7411

My Project will wait, till i buy a hot air gun (or should i buy a rework station?). After i get a hot air gun i will take of the engine and look how its under it. I never done a reballing, but there is for everyone a first time right? Will update this theard if i take it appart!

Special thanks for helping me out to:
nomoresonys
budm
diff

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

These 3 caps seems like they are shorten.
I did freeze them with freezespray to see, if anyone get unfreeze immadiately, but it looks okay.

But what i saw was, blinking LED ld701 wasnt blinking while IC was Cold. So i searched some other topics and found one with maybe broken solder under ic. I will try to reflow it with "baking" Methode. Dont have any heatgun or reflowstation. Hope solderconnection will solve this Problem.

Will Post my result later

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

This one was interesting on how he located and fixed the ones reading shorted, probably a whole different problem tho: https://www.badcaps.net/forum/showthread.php?t=76069

[diif]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

You will find some caps on the main board with low resistance especially around the processor.
Perhaps if you indicated with a photograph where you're seeing the low resistance we'd be ble to assist further.

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Ok, didn't quite get the meaning there, was reading another recent thread, I think he had a bad component making the caps read short, not sure if you have same problem, let me locate it.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Yes i did. See my Post #21 second quote

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Did you do test in post #15?

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Looks like drv-on signal from mainboard is too low to turn on the backlights, guess you could try heating the mainboard with a hairdryer a small section at a time including those caps you mentioned and see if there's any change.

tried on all sections, doesnt change anything

Here's a little test, unplug lvds cable from mainboard to tcon and see if those caps still read short in diode mode, done with tv unplugged and unpowered of course.

these caps, which in my opinion are really short (about 3 caps) have in diode mode unplugged und unpowered: 0,002 V. I tested some other caps to have a reference and mostly they have about 0,2-4V. Seems like these 3 are really shorten?

Do you see an image on screen with a flashlight when you hit menu or anything?

No, cant see any menu. But one half is blinking, flashing and other half is doing nothing.


Now i wait to cool down mainboard. After that i have here freeze spray and will freeze these caps to look, if they will unfreeze if i hit power on button. Shorts will be hot i think, so these caps have to unfreeze immediately

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

When you say shorted caps, what are the resistance readings use Ohm mode?

Wasn´t at home till today, so i´m sorry for my late response. I will do the suggested Test today.

There are a bunch of shorted caps to the ground (continutiy test not diode mode), if i read the resistance i get 2 different readings:
Some caps are at 2,2 Ohms and some have only 0,3 Ohms.
I´ve done readings with mainboard out on TV on my desk (if its necessary). Now i will try test with flashlight and hairdryer

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Do you see an image on screen with a flashlight when you hit menu or anything?

[budm]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I checked some capacitors on the mainboard. Seems like they were shorten. But these are so tiny, i cant read which values they have so i can choose the right replacement capacitor.

Is there anyone, who has an Service Manuell for this TV? I cant finde one

When you say shorted caps, what are the resistance readings use Ohm mode?

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Hairdryer has been known to work on lots of things optos, bga chips, eeproms, different type caps etc etc., do the test in post 15 too.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Looks like drv-on signal from mainboard is too low to turn on the backlights, guess you could try heating the mainboard with a hairdryer a small section at a time including those caps you mentioned and see if there's any change.

These are smd caps, could hairdryer work on this? I thought it only works on elektrolyt caps

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Here's a little test, unplug lvds cable from mainboard to tcon and see if those caps still read short in diode mode, done with tv unplugged and unpowered of course.

[nomoresonys]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

Looks like drv-on signal from mainboard is too low to turn on the backlights, guess you could try heating the mainboard with a hairdryer a small section at a time including those caps you mentioned and see if there's any change.

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I checked some capacitors on the mainboard. Seems like they were shorten. But these are so tiny, i cant read which values they have so i can choose the right replacement capacitor.

Is there anyone, who has an Service Manuell for this TV? I cant finde one

[EUWest]

Re: LG 43UF7709 - Blinking Screen, No Picture, No Sound

I will look if i can get a replacement Mainboard. Meanwhile i will try to fix my Mainboard, because it cant get more worse then now

Thanks a lot for you guys! Will be Post any Updates in this Theard so maybe other People can profit from the experience