LG 42PJ350-UB Sound, No Pic

[johnboy1313]

Red LED on at standby, off when powered up.

Vs = 205V
Va = 65
Vsc = 145V
Vzb = 110

I haven't found where to test -195V. Good fuse on Y-Sus. Good voltages at Z-Sus. Power comes on and off with power button. Panel does not appear to prime. No buzz, no obvious cracks in panel.

I disconnected the LVDS cable and used a 219ohm resistor to short EXT and AUTO GEN on the control board. Still no picture.

I'm thinking Y-Sus. Have any of you had any luck fixing the Y-sus on these?

[capkid]

Re: LG 42PJ350-UB Sound, No Pic

The -Vy (-195V) test point appears to be located below the row of large caps on the Y-Sus. The "-Vy" label might be covered in silicone.

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

For EXT AUTO GEN, a wire jumper works best.

[johnboy1313]

Re: LG 42PJ350-UB Sound, No Pic

Bad control board.

[capkid]

Re: LG 42PJ350-UB Sound, No Pic

Another one saved - nice!

[nick1969]

Re: LG 42PJ350-UB Sound, No Pic

Hi
I have the same model TV with sound only no picture, can you help determine if its the control board or Y SUS board please
Thanks

[capkid]

Re: LG 42PJ350-UB Sound, No Pic

Hi
I have the same model TV with sound only no picture, can you help determine if its the control board or Y SUS board please
Thanks

So, you can just repeat the tests performed earlier:

(1) Check the VS and VA voltages leaving the power supply.
(2) Check VSC and -Vy voltages on the Y-Sus then check Vzb on the Z-Sustain.
(3) If voltages are normal, place a jumper on the EXT_AUTO_GEN points on the logic board to see if test patterns show onscreen.

Edit: Let us know if you need more "how to" info.

[nick1969]

Re: LG 42PJ350-UB Sound, No Pic

Thanks, i will open it up soon and check those voltages first, can you mark on the control board what 2 i need to jump please

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

Two holes adjacent of the "XD" LG chip: marked EXT AUTO GEN. Just put a wire between them, and disconnect the silver-and-black connector at the top of the board.

[nick1969]

Re: LG 42PJ350-UB Sound, No Pic

Vs = 204.6V
Va = 60.6V
Vsc = 23.5V
Vy = 22.9V

im guessing its Y sus board since VSC and Vy voltages are too low

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

Try with the buffer boards disconnected; the buffer boards connect to the Y-sus.

[nick1969]

Re: LG 42PJ350-UB Sound, No Pic

Hi
with the buffer ribbon cable unplugged VSC is 2.5v and Vy 1.9v

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

You need to unscrew the buffer boards completely, just have them connected to the orange ribbons and nothing else.

[Kcristiano]

Re: LG 42PJ350-UB Sound, No Pic

Hi,

I have the same problem on my lg, i check the voltages and i have this:

vs - 213v
va - 63v
vsc - 150v
vzb - 120v

now, i put a wire on EXT AUTO GEN and 3 images appears but just for 1 seconds

1 - http://imageshack.com/a/img838/6903/f319.jpg
2 - http://imageshack.com/a/img839/7836/b6dc.jpg
3 - http://imageshack.com/a/img854/7278/g7kw.jpg

someone knows how fix it?? thanks..

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

Do -Vy and Vsc disappear when that image goes away? What about Vs and Va?

[Kcristiano]

Re: LG 42PJ350-UB Sound, No Pic

hi,
thanks to wast your time with me...

i think vsc dissapear when image goes way..my mulltimeter just go to 500v..so when image goes away give me 1 on multimeter, when image comes, multimeter give me +-200v depends the image...

vs and va no change...

[Kcristiano]

Re: LG 42PJ350-UB Sound, No Pic

so Tom66, you don t know what it is???

[paulnetv]

Re: LG 42PJ350-UB Sound, No Pic

Hi guys, I too have a problem with this 42PJ350 set.

Much as above.
Va = 60.4
Vs = 204.4
Vsc = 146.1
-Vy = -196.2
Vzb = 110 however after a few seconds this begins to drop, if checked after 5 minutes, this has all but disappeared.

I have no buzz from YSUS and no glow on the screen in dark room.

I have no flashes at all on the CTRL board although the voltages to it appear to be fine also the onboard regulators are working and giving out 3.3v & 1.2v as would be expected.

I have linked Stby with RL_ON and M_ON at the mainboard with 220R resistors in order to make the screen glow but to no avail. I still get no buzz or glow.

I scoped J43 on the ZSUS board labelled "ZSUS_Waveform" for all I don't know what to expect here I get a pretty constant 17.75volts and no waveform.

From the above, I am almost sure PSU, Mainboard (Computer) and YSUS/buffers are all ok.

Can anybody add anything I can test here to confirm my suspicions of CTRL board faulty or ZSUS board. I can't be sure which it is.

Thanks in advance for any replies.

P.S. It is getting on here in the UK so I may not reply for a few hours.

[paulnetv]

Re: LG 42PJ350-UB Sound, No Pic

Bump...

Can anyone think of where to go next with the problem on this set?

I'm scratching my head now.

[paulnetv]

Re: LG 42PJ350-UB Sound, No Pic

Would it help if I say please