LG 50 PS 3000 - Still No picture after ZSUS repair

[Ven]

Hi,

I have a LG PS 3000. There is no picture but sound is OK. There was a very bad quality picture in the very beginning but I saw that only once. Never any picture appeared again.

After finding a similar LG TV service book. I found that :

• Power Supply Va 64V is ok
  Power Supply Vs 192 V is OK
  Power Supply 5V is OK
  
  YSUS 64V Fuse is OK
  YSUS 192V Fuse is OK
  YSUS 5V is OK
  YSUS 5V is OK
  YSUS -VY is -175V is OK
  YSUS VSC 138V is OK
  
  ZSUS Zbias is 0V

3 mosfets were all short circuit on the ZSUS. I found from ebay that there is Repair Kit just for this repair included all Mosfets, a zener diode, some resistors and some capacitors. ( http://www.ebay.co.uk/itm/281685799774 )

So I replaced all now I can see Zbias voltage came back. Zbias is OK now. But there is still no picture.

I connected a DVD player and can hear the sound.

Can anyone help on this please ? Thanks

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Got the same set here same issue only one fet short, does the screen light up in a dark room ? Also did you check the little fusible resistor which I belive is yellow near the input connector on the Zsus heard that can blow if the fets do ?

[dick_barton]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Run test pattern.
https://www.badcaps.net/forum/showth...+control+board

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Run test pattern.
https://www.badcaps.net/forum/showth...+control+board

Might not be that as Zbias is 0 Sounds to me like fuse is gone.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Got the same set here same issue only one fet short, does the screen light up in a dark room ? Also did you check the little fusible resistor which I belive is yellow near the input connector on the Zsus heard that can blow if the fets do ?

Yes screen lights up, I can see that. But It was already lighting up before too.

And yes you are right it s a yellow colour fuse, it is OK, and there is another fuse on ZSUS, which is also ok.

Also, 17V is OK coming from YSUS, as explained on service manual.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Might not be that as Zbias is 0 Sounds to me like fuse is gone.

Zbias is OK now, after I changed that kit bought from ebay. It is same as shown on the sticker on the back panel.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Run test pattern.
https://www.badcaps.net/forum/showth...+control+board

Thank you for the reply but it mentions for Samsung and Panasonic TVs. Mine is LG. Am I missing somethings ?

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Ok then possibly your mb or control board isnt working, jump the auto ex gen pins on the control board and start the Tv with the Lvds cable removed.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Ok then possibly your mb or control board isnt working, jump the auto ex gen pins on the control board and start the Tv with the Lvds cable removed.

OK, I have to study this first because I dont know how to do it.
BTW, 2 x 3.3Volts and another 2.5 V is OK on control board as shown on service manual. There are 2 LEDs one is solid and other one is flashing.

How to jump ex gen pins on the Control Board, do you mean Auto Gen(Thats what I see on the Control Board) ?
If so it is a free socket, 4 pins and no connection.

And If I manage to do that, how is it going to help me ? Thanks

[mmartell]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Try jumping middle two pins. If you get test patterns then your main board is likely shot.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Try jumping middle two pins. If you get test patterns then your main board is likely shot.

I managed to put it in Auto Gen. A series of patterns appeared on the screen, all look good.

So in this case main board is faulty ?

Thanks

[vinceroger69]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

yes you will need a replacement main board

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Yes the Mb is failed, its probably the bga solder on the cpu which is the device under the heatsink. Try reflowing the cpu.

[dick_barton]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

You can try to reflow it yourself since you would have nothing to lose.
I'm sure that someone who has successfully carried out this task would be willing to advise you.

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

You can try to reflow it yourself since you would have nothing to lose.
I'm sure that someone who has successfully carried out this task would be willing to advise you.

I have check my 50ps3000 repair video out shows that them boards have issues with Bga solder, I did actually reflow that and try it in another one I got that has bad Zsus but it wadnt perfect the Hdmis didnt work and it sounded odd so guess it probably needs reballing.

Im making a video on the chips used on these Lg boards, Lg's XD engine get very hot and Lg just dont heatsink them well enough so they fail very common.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

yes you will need a replacement main board

Just in 1 min after switch-on Main chip on the Main Board is very very hot, nearly can't touch to heat sink. Thank you.

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Just in 1 min after switch-on Main chip on the Main Board is very very hot, nearly can't touch to heat sink. Thank you.

On the replacement board you should remove the heatsink and reapply some thermal plaster to glue to heatsink down (only use silicon thermal plaster) then maybe add a little fan to it as the pm chips get VERY hot and will die fast. Also use fresh thermal plaster as it works alot better than the orginal thermal pad which is probably dried up on the heatsink so remove that.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Thank you everyone, I will update as soon as I have any news.

[Ven]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

UPDATE : After replacing the Mainboard Tv is working fine now.
So there were 2 problems.
One was Zbias and other one was Mainboard itself.

Thank you all for your help.

[ReeceyBurger123]

Re: LG 50 PS 3000 - Still No picture after ZSUS repair

Awesome work now cool that chip better some how