LG 42LC2D no picture

[bestjm]

I have an LG 42LC2D tv that recently lost picture. When I turn the unit on I get a click, the red standby light blinks green 12-14 times and then turns solid. When I press the power button, it takes several seconds to turn off. I have replaced several caps including one visibly blown one. The unit is still not working. I started disconnecting wiring harnesses. When I disconnect the 13 pin harness, the unit will power on correctly, but still no picture. With the set still on, I reconnected the harness and I have video. The pictures included have the harness I am talking about circled. Any ideas? Thanks in advance.

[dick_barton]

Re: LG 42LC2D no picture

So what DC voltages do you have on that harness when it is connected to the mainboard and you have no picture?

[bestjm]

Re: LG 42LC2D no picture

I took these readings this afternoon. The second 5V pin was steadily dropping. When I first took the reading, it was showing almost 1.5v.

AC DET - OL
RL ON - 1.85v
ST 5V - OL
GND - 0
INV ON/OFF - .012v
5V MNT - .072 dropping
POL/INV - 1.112v
ST 5V - OL
GND - 0
PWM - .118v
6.0 V - OL
GND - 0
LIVE ON - 1.476v

[budm]

Re: LG 42LC2D no picture

I took these readings this afternoon. The second 5V pin was steadily dropping. When I first took the reading, it was showing almost 1.5v.

AC DET - OL
RL ON - 1.85v
ST 5V - OL
GND - 0
INV ON/OFF - .012v
5V MNT - .072 dropping
POL/INV - 1.112v
ST 5V - OL
GND - 0
PWM - .118v
6.0 V - OL
GND - 0
LIVE ON - 1.476v

What is the meter DCV range set to, it should not be showing OL on ST5V for example. You need to retest those Voltages again, also need to look for the Inverter power supply Voltages.
Right now you are saying you do not have pictures, which you will not see the pictures because the Blacklights are not on for you to be able to see the image on the screen because the main board is not sending the INVERTER ON (BL-ON) signal.

[bestjm]

Re: LG 42LC2D no picture

Sorry. I must have had the range too low.

AC DET - 0v
RL ON - 1.85v
ST 5V - 4.98v
GND - 0
INV ON/OFF - 0
5V MNT - .08v
POL/INV - 1.112v
ST 5V - 4.96v
GND - 0
PWM - .10v
6.0 V - 6.13v
GND - 0
LIVE ON - 1.476v

It looks like the inverter power supply voltages are all above 24v. Thanks for your help.

[bestjm]

Re: LG 42LC2D no picture

I'm still looking for help with this issue. If anyone has any advice I would appreciate it.