LG 42PJ350-UB Sound, No Pic

[adamp91gvm]

Re: LG 42PJ350-UB Sound, No Pic

I have the same tv mines on and working but it goes off then comes back on after about 5 mins then does it more. More it is on

[paulnetv]

Re: LG 42PJ350-UB Sound, No Pic

For the record, this one was a faulty ctrl board.

[senndogg]

Re: LG 42PJ350-UB Sound, No Pic

Hello!
Another case of NO picture 42PJ350.

Voltages:
vs - 205v
va - 60v
vsc ~20v
vzb - 117v
-vy ~15V

As Tom suggested in post 11 i disconnected the buffer board and saw only a slight decrease in voltages of vsc and -vy, but these remain still too low.

I have minimal experience with plasmas and troubleshooting this is an enjoyable experience.

I have the Ysus in my hand, where do i start?

thanks in advance!

[senndogg]

Re: LG 42PJ350-UB Sound, No Pic

Today decided to go further. I am inspecting the place of interest, the smps of the Vy.

Here are some pics. In the last pic i made a small debrief of the components an traces.

[tom66]

Re: LG 42PJ350-UB Sound, No Pic

Try checking the YPS FETs (or YPN FETs) if they are shorted the Vsc/-Vy can go down.

[senndogg]

Re: LG 42PJ350-UB Sound, No Pic

sorry for the noob question Tom, but which are the YPN/YPS Fets?

At the moment I am suspecting sth. The voltage at the smps IC capacitor is fluctuating between 6-9 V. The other leg of the diode is steady 18V.

[Lacio30]

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.

Hello all,

brand new to this forum and having exactly same problem as Nick1969 bellow. As there is no answer to his problem can you please let me know whether I should change Y-SUS board or just changing control board will fix it?

I have same model TV and same reading as bellow. Help please

08-25-2013 07:53 AM
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

[stevey]

Re: LG 42PJ350-UB Sound, No Pic

Same problem. After running the EXT AUTO GEN test I found the panel had a great picture. I was able to sub the main board and everything worked. Thanks everyone.

[ReeceyBurger123]

Re: LG 42PJ350-UB Sound, No Pic

Same problem. After running the EXT AUTO GEN test I found the panel had a great picture. I was able to sub the main board and everything worked. Thanks everyone.

Good work

[Nexxtron]

Re: LG 42PJ350-UB Sound, No Pic

Hello. I have the following voltages on a LG 42PJ350 TV

Vs = 205V
Va = 65
Vsc = 19V
Vzb = 114

I need some directions as to what to do next. Please note that the Vsc is only 19 volts.

Regards

[ReeceyBurger123]

Re: LG 42PJ350-UB Sound, No Pic

Remove buffer retest vsc.

[Nexxtron]

Re: LG 42PJ350-UB Sound, No Pic

I completely removed the buffer board and tested Vsc and got 1.9V. When I replaced it, I got 19V again

[rapbalance]

Re: LG 42PJ350-UB Sound, No Pic

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.

My Vsc varies between 112 and 137V, and my Vy between 163 and 180V. Is this normal? Or is it faulty Y-board?

[PREDATOR1]

Re: LG 42PJ350-UB Sound, No Pic

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

Hello guys!
Does anybody know where I should look further if VSC and Vy voltages are bad even with the buffer board disconnected from the Ysus?
I already replaced two 30j124 and two 30f124 IGBTs, as they were shorted and the power supply was entering in protection mode.
Thank you!

[PREDATOR1]

Re: LG 42PJ350-UB Sound, No Pic

No one?

[Unspun01]

Re: LG 42PJ350-UB Sound, No Pic

Hi.

What are the EXACT component locations of the parts that you replaced?

IGBTs are gate controlled devices, You may have found the shorted IGBTs, but the low resistance gate drive resistors may have opened up when the IGBTs shorted out. The low-resistance resistors on the bottom of the board connected to the IGBT gate pin should be tested as well as the driver ICs, but first lets test the gate resistors.

Visit shopjimmy:

www.shopjimmy.com/lg-ebr66607501-ysus-board.htm

Download the hi-resolution photos of the TOP and BOTTOM of the board, and highlight the components you replaced (in RED color) and upload them here for us to review.

In fact, the shopjimmy board photo has the insulation foam still installed. It may be better to upload your own high-resolution photo with the foam removed to better see the traces and locations.