LG 32lh20r-ta no picture, backlight only

[kumag]

Hello fellow tech'n.. i have checked all printed voltages on power board and its ok except the power_on voltage that reads 2.0 when turned tv on. The 12v supply to panel drops to 7.2v but when lvds ribbon detached it resumes to 12v. beforehand...I saw some image retention and color bars in horizontal order on and off. The tv turns on fine but no image no osd just a clear screen with backlight on..

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

some attachments..

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

On the first diagram that you drew on, what do you measure on the 5V supply to the transistor? I'm guessing that pin 2 (labelled Power On) is a connector and not an IC.

If you measure about 2v on the 5v line then you need to trace what is dragging that 5v line down. Look at the 5v supply regulator/caps itself. Look at the 3v3 regulator hagging off the 5v line. If you isolate the input of the 3v3 regulator and the 5v line measure normal again, obviously 3v3 side has a fault.

If you actually measure 5v on the 5v line, then you need to trace where pin 2 on the connector (im guessing its a connector) goes to and post up your findings.

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

Also, what happens to the 5V when you detach the lvds ribbon?

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

thanks for your response sir.. 3.3 and 5v is ok. only the 12v from Q1003 vary its output.. and also the power_on pin..

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

What does the 12v line measure at the top of the inductor L1006 (labelled 12v small)
Also, in your diagram it says "drops to 7.2v" Do mean to say you measured 12v and then something turns on then the voltage drops?

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

Where does pin2 (power on) go to? Follow the cable..

more pictures please

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

its 12v on top of L1006 up to s1 of q1003..when i turn on the tv the drain side voltage drops to 7v2.. but when lvds ribbon detached it resumes to 12v

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

On that diagram on the far right, what does it read just before +12V LCD?

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

what does the Panel_ON net measure when LVDS cable is left plugged in then pulled out?

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

On that diagram on the far right, what does it read just before +12V LCD?

thats the point that is unstable..

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

what does the Panel_ON net measure when LVDS cable is left plugged in then pulled out?

i think im going to do that later sir.. my country is having bad weather today and my internet is badly slow... many thanks for now for helping me sir nibbletr..

[niblettr]

Re: LG 32lh20r-ta no picture, backlight only

thats the point that is unstable..

No, I mean the writing on the diagram. (quality of photo is bad)

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

some pics and service manual..

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

On that diagram on the far right, what does it read just before +12V LCD?

it's +5v_

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

hello.. i would like to ask what is the right actual power_on voltage to expect on this model.. because i read it at 2v0.. i am very confused.. Another thing i noticed was when i get closer to its psu, there was a not so loud ballast-like-sound.. seems it operates at low frequency.. there is a built-in tact switch on mainboard.. is it safe to push while the tv is on?

[kumag]

Re: LG 32lh20r-ta no picture, backlight only

hello...