LG 32LE4500 LD01D - stays black no pic

[wuffwuff2003]

Hello, The Tv Switches ok, Led turn from Red to White. Relais on power pcb = OK - Inverter stays out of order, Image black!
Voltages on Powerboard all Ok. 3,5V / 12V / 24V
Voltages from Mainboard to Powerboard:
P-Dim 3,4V
A-Dim 0V
Inv 0V
Error 0V
The main Inv Transistor on Mainboard is working.
What can I also try to find the fault?
Thanks?

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

"Inv 0V" The main board is not getting the BL-ON signal from the main board to turn on the backlights circuit.
"The main Inv Transistor on Mainboard is working." What do mean by working, if it is working than the INV (BL-ON) should go high when the TV is ON (BL-ON: <1VDC = OFF, >2VDC = ON), if the transistor is working then INV signal should toggle.
Do you have the circuit diagram?

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

Hi yes I have the circuit Diagramm, When I pull out the Error ligne from the connector, and when I took out the base resistor of the Transistor, then the backlight light up, so the Inverter board is Ok. I think the Mainboard does not send the Inv_on LOW Signal (The Signal on the Base Transistor stays all the time 1V) and it keeps the Error ligne to gnd. So its the Mainboard I think. But what on Mainboard. Also soemthing strange is that the LED of the digital outport (Sound) doesn't light up, but all the voltages are ok on the board. Thanks

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

Yes, you do have main board problem or the ERROR signal is stopping the main board to send out BL-ON, as to the exact cause I do not know.
I also do not if the ERROR Line = LOW = NORMAL, or =HIGH = NORMAL.
Can you upload the service manual? May be you need to figure out what the ERROR line is for.

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

Hi have figure out the error line yes. When i disconnect Error Line and let the BL-Line connect theres no backlight. Same when I Change . I must disconnect BOTH lines to light up the Backlight. I try to upload it now yes.
Best regards

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

The Attachment

[dick_barton]

Re: LG 32LE4500 LD01D - stays black no pic

Error_Out looks like an output from the power supply to the main board. R486 is connected to it and should have 3.3V on it. Have you checked that it is there?

Also have you checked the transistor Q405 using your meter in diode mode to check that it's OK and not shorted.

INV_CTL is normally High so the collector will be at 0V. When INV_CTL goes low the collector should go to 3.3V

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

Hi,
Q405 is full operating, I have test it after desoldering with an Transistor tester, it's in good condition, same as R421, R426, R425, R419. I have 3m3V on Collector, and 0,8V on Base of Q405
Error Out has 0V (pulled down to ground) , R486 is ok, an the 3,3V on R486 are also ok, but pulled down to ground.
Why can Error be pulled to ground on the power supply, when all the voltages are ok at the PS?
Best regards

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

Hi just downloaded the circuit Diagramm of the PS, the error isn't connected to the PS.

[Diah]

Re: LG 32LE4500 LD01D - stays black no pic

Hello, Image black!

could you explain if you use torch light on the screen. do you see any dark image on the screen or not ?

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

Looking at the PS diagram, the power supply board does not generated the ERROR signal, the ERROR signal is generated by the backlights circuit, the signal is just being routed through the power supply board.
Same for the INV-ON, ADIM, PWM-DIM, they are routed through the power supply board for clean wiring.

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

Can we see the pictures of the whole backside of the TV showing all the board?

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

I've also searched a schematic for the led Driver board, but I can't find it: Model Number of the Driver board: 37T06-D04
(TCON Board is: T370HW04)
Thanks
Best regards

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

When I turn the Backlight on Manually (disconnect error and inv-on line from the Driver board) , the Screen is dark triggered, the LCD is black .. (closed) But nothing on the Screen, no OSD no Images, just black.

[Diah]

Re: LG 32LE4500 LD01D - stays black no pic

yours LG built year 2011, do you think your backlight LED survive till now ??
its first generation of LG LED , they work direct. no protect circuit to give error signal.

i asked did you see dark picture with turch light in dark room,, this is easy way to know where need to check

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

The ERROR pin may or may not be used, based on the maker of the LCD panel as shown in the chart, so lot of those resistors for PIN 24 may or may not be present.
What is the maker and model of the LCD panel?

[Diah]

Re: LG 32LE4500 LD01D - stays black no pic

photos of whole back better than talking.. its had extra led driver connected with t-con ?

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

What is the model number of the LCD panel? is it made by AUOPTO? if that is the case then pin 24 is not used and the ERROR out signal pin, it is PWM DIM pin per chart.

[budm]

Re: LG 32LE4500 LD01D - stays black no pic

I've also searched a schematic for the led Driver board, but I can't find it: Model Number of the Driver board: 37T06-D04
(TCON Board is: T370HW04)
Thanks
Best regards

Are you sure? Those numbers indicate 37" panel by AUOPTO.

[wuffwuff2003]

Re: LG 32LE4500 LD01D - stays black no pic

Hi, I will do a pic of the TV , I checked the error Signal, and it's right this Error Signal is the PWM Signal. Here are Voltages of the Invert Board, when I OPEN the Error Circuit (Inv Board to Mainboard)
PDim = Error : 6,4V
VDim = P.Dim: 4V
Ena = A.Dim: 3,6V
Det. = Inv ON: 0V

When I Close the Error Line now, only the PDIM Voltage drop down to 0. The other Lines are OK. On the other pic you see the real schematic as it is on board.

Thanks