LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

This is done with the TV powered ON? You have 12V feeding the T-CON fuse F1 but the switching power supplies are dead. Based on those Voltage readings you have made the T-CON board is dead at this point.
BTW, I hope you did the test correctly.

I'm pretty sure I did the test correctly. I had to run my pos. probe over a file to 'sharpen" it a bit as I wasn't sure I was hitting those small areas correctly.

In any case, I've got a TCON on its way.

EDIT: Yes, the test was done with the TV on.

[budm]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

vcc = .026
vcc18 = .025
vgh = .022
vgl = .050
vdd = .018
vcore = .022
hvdd = .024

This is done with the TV powered ON? You have 12V feeding the T-CON fuse F1 but the switching power supplies are dead. Based on those Voltage readings you have made the T-CON board is dead at this point.
BTW, I hope you did the test correctly.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

please check the dcv (when tv is turned on) at those test points i have marked: Black probe on the chassis.
Vcc =
vcc18 =
vgh =
vgl =
vdd =
vcore =
hvdd =

vcc = .026
vcc18 = .025
vgh = .022
vgl = .050
vdd = .018
vcore = .022
hvdd = .024

[budm]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

Please check the DCV (when TV is turned ON) at those test points I have marked: Black probe on the chassis.
VCC =
VCC18 =
VGH =
VGL =
VDD =
VCORE =
HVDD =

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

Yes, that is the cable.

Awesome, thanks.

I know what an oscilloscope looks like but have never used one. For further reference, what would the oscilloscope tell me about the LVDS cable?

[dick_barton]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

For clarification, the LVDS is the cable that runs from the main board to the TCON, correct?

Yes, that is the cable.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

At this point I'd really like to verify the LVDS on a oscilloscope, if there is any possibility for you to get the hands on one...
BTW: did you already try do disconnect only one of the ribbon cables on the Tcon that go to the LCD screen, then vice versa... in order to see if there maybe half of the screen comes up?

I did that and there was no change. As for an oscilloscope, I don't have access to one.

For clarification, the LVDS is the cable that runs from the main board to the TCON, correct?

[CapLeaker]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

At this point I'd really like to verify the LVDS on a oscilloscope, if there is any possibility for you to get the hands on one...
BTW: did you already try do disconnect only one of the ribbon cables on the Tcon that go to the LCD screen, then vice versa... in order to see if there maybe half of the screen comes up?

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

if you put the original main board, will be easy to check after this static, by moving the load from MB step by step.

first disconnect LVDS from MB side, and check, static remain or not, if no more you hear. then put back LVDS to MB and disconnected LVDS from T-CON and check.. still you hearing the noise mean LVDS, if static no more, go further to T-CON and so on till the ribbon cable to LCD,

if at the first point of LVDS disconnected from MB and remain to hear static noise, then disconnect the speaker and check them of shorted. if they are well.. disconnect the IP section and check..

this is easy way. if your measurement way you have lack or not sure of them.

I can try that but before I do, I want to clarify what I mean by static: it's the white noise you hear when the TV isn't tuned to a good channel.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

I put the original main board in, same result except now I don't hear snow from the speakers.

This has to be a bad TCON board.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

Originally Posted by budm
BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.

Wouldn't be the first time we got a run around.

I feel bad enough, guys.

[CapLeaker]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.

Wouldn't be the first time we got a run around.

[Diah]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

I hear static (snow) when I turn it on.

if you put the original main board, will be easy to check after this static, by moving the load from MB step by step.

first disconnect LVDS from MB side, and check, static remain or not, if no more you hear. then put back LVDS to MB and disconnected LVDS from T-CON and check.. still you hearing the noise mean LVDS, if static no more, go further to T-CON and so on till the ribbon cable to LCD,

if at the first point of LVDS disconnected from MB and remain to hear static noise, then disconnect the speaker and check them of shorted. if they are well.. disconnect the IP section and check..

this is easy way. if your measurement way you have lack or not sure of them.

[budm]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

BTW, it took a little over 30 posts (starting at post 33) just to find out that the DCV measurement were made wrong on the T-CON board, I almost got to the breaking point, I knew it was the measurement error when it did not make any logical sense in the readings results.

[CapLeaker]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

Yep... change that main board out for the original one. If you have a oscilloscope handy, you could try measuring the LVDS, if the TV turns on.

[budm]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

At this point we know the power supply and the LED driver are working so you can leave the power supply board in place, I would put the old main board back in place and go from there.
BTW, and no one else had worked on the TV before you received it, we hope.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

I suspect Budm may be eluding to the fact that when you replaced the original fuse and had the led blinking this was probably due to the faulty led strip in the backlight.
Once you repaired the backlights I would have expected you TV with it's original boards to be working.

Worth a shot if I can get a hold of the original boards. I started working on this TV a month ago. I'll need to look for them.

[dick_barton]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

I suspect Budm may be eluding to the fact that when you replaced the original fuse and had the led blinking this was probably due to the faulty led strip in the backlight.
Once you repaired the backlights I would have expected you TV with it's original boards to be working.

[JDC]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

I think it would be best for us all if we called it a night for right now and start fresh again in a day or two. I really appreciate everyone's help and I apologize for not being more thorough. I'll do better next time, for sure.

[dick_barton]

Re: LG 47LN5200_U: PWR, MAIN, and all LEDs replaced, no picture

As budm says it is time for a recap so we all know the next starting point.