Insignia NS-50L240A13 - Not Turning On

[ECU_Techie]

Hi all,

I have a 50" Insignia LCD TV that will not power on or show signs of life. The gentleman I got the TV from said it one day would not turn on and would not even get the red standby light in the front corner anymore.

I opened it up and tested the PS fuse, it has 120V running through it. Testing the pin outs on the cable connecting the PS board to the main board I get the following voltages:

• 12V - 11.94V
• 12V - 11.94V
• GND
• GND
• 12V - 11.83V
• 12V - 11.83V
• GND
• GND
• PON - 2.93
• 5V1 - 5.14V
• 5Vsb - 5.14V
• PWM - 3.32V
• BON - Fluctuates between 0.01V and 0.00V. What does BON power?

For the voltages running from the main board to the IR board I read:

• IR - 2.18V
• 5V - 5.11V
• GND
• LED - 0.10V Could this be the reason why the LED won't light up?

Thanks in advance!

[budm]

Re: Insignia NS-50L240A13 - Not Turning On

BON - Fluctuates between 0.01V and 0.00V. What does BON power?

BON: Backlights ON (BL-ON), so it looks like your main board is not sending the Backlights ON command to turn on the backlights circuit.

[dick_barton]

Re: Insignia NS-50L240A13 - Not Turning On

BON....I would think it means Backlight On. With a bright light check carefully to see if you have a picture on the screen. It may just be that the backlights are not on.

If you disconnect the mainboard from the power supply do the backlights come on.

If not with the mainboard still disconnected use a 1K resistor and jumper it between 5Vsb and PON and another 1K between 5vsb and Bon

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

Yep, that makes sense! There is no picture on the screen when I hold a flash light to it. Like I said, not even the red LED comes on down in the front corner. Unconnecting the cable going to the main board from the PS board did not bring a back-light either.

There is a cable running from the PS board to the left side of the screen. I assume that is the cable which powers the back-light? It is reading 0V down the entire connector. I don't have any 1K resistors so wasn't able to try and jump it.

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

Does anyone know what the proper voltage to the LED indicator light is on TV's? I measured the voltage right to a leg of the LED itself and it is reading 0.09V.

I just finished reading over Budm's LCD troubleshooting PDF which was informative. Thank you for creating that sir. You mentioned that if the 5Vsb pin out was showing voltage that the indicator light should always be on. Any idea why this might not be the case?

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

An update, I took two resistors and jumped the pins of 5Vsb and BON and then 5Vsb and PON and the backlight lit for a second and went back off. I left the resistors on the pins and tested the voltage at the BON pin and with the resistors on the respective pins still, BON reads 5.15V. Also, two of the pin outs on the cable going from the PS to the back-light behind the panel read around 5V.

So does this point to a more then likely issue with the main board? I was trying to source another main board, and everywhere is out of stock. One company says that they can repair it, but still going to run $100 dollars, so i'd like to be sure before going that route. The company is PTS Electronics, anyone deal with them before?

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

It has to be the main board. If I unplug everything from the main board and plug the tv in with the resistors in the pin outs of the one cable, the back-light comes on. If I only have the power cable to the main board plugged in, the back-light will not come on until I unplug the power cable from the main board. At that point the back-light comes back on.

I got the back-light to stay on by putting in a third resistor going between 5Vsb and PWM. In the picture below, you can see the three resistors and through the holes of the backside of the panel you can see the back-light is on.

[dick_barton]

Re: Insignia NS-50L240A13 - Not Turning On

Lift the BON pin out of the connector at the power supply board end. With the mainboard connected and using a jumper resistor between 5Vsb and BON pin (now left empy on the power supply board) and see f you have a picture when you switch on.

[budm]

Re: Insignia NS-50L240A13 - Not Turning On

Lift the BON pin out of the connector at the power supply board end. With the mainboard connected and using a jumper resistor between 5Vsb and BON pin (now left empy on the power supply board) and see f you have a picture when you switch on.

+1.
We know that the problem is from the main board due to the lack of the BL-ON signal that is being kept low.

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

No dice. Still no picture or back-light when the main board is connected to the PS board.

[budm]

Re: Insignia NS-50L240A13 - Not Turning On

No dice. Still no picture or back-light when the main board is connected to the PS board.

You have to remove the BL-ON wire from the connector first (the connector is not removed, only the BL-ON wire is removed) and then use the resistor between the BL-ON pin and the 5VSTBY on the power supply board to force on the backlights circuit.

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

Ah, I gotcha this time. Ok, I took the BON pin out of the PS board end of the cable connector and plugged everything back up to the main board. I plugged the tv in and then jumped a resistor between the 5Vsb pin and the now empty BON spot on the connector.

The back-light came on now with the cable connected on both ends, but still no picture. Just the back-light staying on constant. Thanks for that good piece of troubleshooting advice guys.

[budm]

Re: Insignia NS-50L240A13 - Not Turning On

Ah, I gotcha this time. Ok, I took the BON pin out of the PS board end of the cable connector and plugged everything back up to the main board. I plugged the tv in and then jumped a resistor between the 5Vsb pin and the now empty BON spot on the connector.

The back-light came on now with the cable connected on both ends, but still no picture. Just the back-light staying on constant. Thanks for that good piece of troubleshooting advice guys.

What we have you done is to verify if the backlights circuit is OK or not, it is OK.
So you have at least 2 problems:
1) The main board is not sending the command signal to turn on the backlights.
2) The main board video section is bad or the T-CON board is dead so you are not getting the pictures on the screen.
We know at least the main board is bad due to lacking the BL-ON command signal.

[ECU_Techie]

Re: Insignia NS-50L240A13 - Not Turning On

Thank you both for the help on this tv. I also believe it is the main board as the IR board with indicator light also seems to have an issue. I did a quick test on the T-Con board connector pins and most of them don't read a voltage except for like one or two of them.

I believe at this point I will take my chances and mail the main board in to PTS Electronics and see if they can fix it. Once I hear back from them or get the board back, I will provide an update to where this tv stands. Once again, thank you both!

[dick_barton]

Re: Insignia NS-50L240A13 - Not Turning On

What we have you done is to verify if the backlights circuit is OK or not, it is OK.
So you have at least 2 problems:
1) The main board is not sending the command signal to turn on the backlights.
2) The main board video section is bad or the T-CON board is dead so you are not getting the pictures on the screen.
We know at least the main board is bad due to lacking the BL-ON command signal.

+1 as Budm says, no picture when the backlight are forced on does imply you have other problems with the set.