Lg 42PJ350 no Picture

[tom66]

Re: Lg 42PJ350 no Picture

That doesn't seem bad. Also I recall that the logic board does not use 15V it just uses wiring harnesses to pass it thru to Z-sustain.

[ajshoe]

Re: Lg 42PJ350 no Picture

you are correct on this - 15V passes thru to Zsus - gad design. assume my EBAY Ysus is bad - not supplying 15V

[tom66]

Re: Lg 42PJ350 no Picture

or Z-sus has short/overload to 15V, worth checking maybe with an external PSU...

[ajshoe]

Re: Lg 42PJ350 no Picture

originally got tv that wouldn't turn on, clicks and then shut down. I assumed bad Ysus. bought EBAY Ysus - set now comes on with no display - all voltages good from PSB. why can't I disconnect Zsus ? then check 15V. if good, Zsus is shorting it. if still bad - Ysus not generating proper 15V.

[buchman]

Re: Lg 42PJ350 no Picture

Have you resolved your problem? I have the same problem with the same TV. When everything is connected it's burning out one of the IGBTs on the ysus board. But, if I disconnect the white ribbon between the zsus and the control board then everything is fine.

[ajshoe]

Re: Lg 42PJ350 no Picture

just got new EBAY logic bd - let u know as soon as I install it. do u have all PSB voltages except 15V on ySUS bd ? my set stays on but no display (15V missing to Zsus bd). I believe logic bd commands Ysus bd to turn on 15V to Zsus bd. yours sounds like Zsus bd bad causing Ysus Igbts to blow - check your Zsus bd diode

installed new logic bd - same issue. plasma stays on - all voltages are present from PSB but NO 15V to Zsus bd. I must have bad Ysus board. does anyone have schematic of Ysus bd ??

[buchman]

Re: Lg 42PJ350 no Picture

All my voltages are ok except 15V.

[buchman]

Re: Lg 42PJ350 no Picture

Test all your IGBTs on YSUS board and the dual diodes. That was my problem with the ysus.

[ajshoe]

Re: Lg 42PJ350 no Picture

?? set works now? I checked all the IGBTs and they were good.

in post #25 - you said u disconnect white ribbon cable between Zsus and logic bd - there is no ribbon cable between them ! did u mean Ysus and logic bd ??

[buchman]

Re: Lg 42PJ350 no Picture

?? set works now? I checked all the IGBTs and they were good.

in post #25 - you said u disconnect white ribbon cable between Zsus and logic bd - there is no ribbon cable between them ! did u mean Ysus and logic bd ??

Probably we have slight difference in tv model

[ajshoe]

Re: Lg 42PJ350 no Picture

ill take some pics of plasma - don't think they could be different. Ysus board is on left and Zsusu bd is on right side when looking at the back of the 42pj350 set. Th Zsus connection to the logic bd is a cable with individual white wires. The Ysus connection to the logic bd is a white ribbon cable with push slide in connectors. is your set a 42PT350 ?? it has both cables going from the logic bd to the Zsus and Ysus bds as ribbon cables.

[buchman]

Re: Lg 42PJ350 no Picture

yup, mine is 42PT350R.

I can't understand what is feeding what... the T-CON BOARD FEEDS THE YSUS AND ZSUS or vise versa?

[ajshoe]

Re: Lg 42PJ350 no Picture

R u asking about 15v line ?

[buchman]

Re: Lg 42PJ350 no Picture

R u asking about 15v line ?

yes

[ajshoe]

Re: Lg 42PJ350 no Picture

From what I can tell the 15 volt line is generated on the Ysus board it is then routed to the logic board and then goes through the logic board to the Zsus board. the logic board does not use the 15 volt line whatsoever - 15v is just routed thru logic bd. This is why I was asking for Ysus schematic. I'm assuming your TV is not displaying anything just like mine. I have another Ysus board which I will repair and try and let you know what happens.

[buchman]

Re: Lg 42PJ350 no Picture

From what I can tell the 15 volt line is generated on the Ysus board it is then routed to the logic board and then goes through the logic board to the Zsus board. the logic board does not use the 15 volt line whatsoever - 15v is just routed thru logic bd. This is why I was asking for Ysus schematic. I'm assuming your TV is not displaying anything just like mine. I have another Ysus board which I will repair and try and let you know what happens.

my ysus is working great now I believe, I think my problem is
t-con or zsus

[buchman]

Re: Lg 42PJ350 no Picture

just tested my ysus board. coudn't find anywhere 15V.
The maximum I am getting is 4.3V.

[ajshoe]

Re: Lg 42PJ350 no Picture

yes - exactly same as mine - thats why i posted on this thread. post a pic of your Ysus. u should have a label on the board - 15V. this is what goes thru logic bd to enable Zsus bd

[buchman]

Re: Lg 42PJ350 no Picture

Some place it say 15V and some place it's 15VF. Why?
I am getting 4.3V.

There is a junction wire on the left bottom of the board that say 5VF and I am getting a reading of 0.5V.

[ajshoe]

Re: Lg 42PJ350 no Picture

check that 15V again - watch it as u turn set on. is it going to 18V then slowly goin down to 4.1V ? thats what mine is doing - when it first goes to 18V - there is a slight buzzing noise (no display) and then it fades away as 15V goes to 4,1V