Insignia NS-50d40SNA14not turning on

[nomoresonys]

Re: Insignia NS-50d40SNA14not turning on

If these are your strips (pic found on ebay and some blog), you have a total of 8 x 4 = 32 LEDs. If they are wired into 2 banks of 16 and you are measuring 89V off each bank with an LED tester, then I would assume they are 6V LEDs and you have one short LED in each bank.

Looks like it's time to teardown to the leds then.

[budm]

Re: Insignia NS-50d40SNA14not turning on

1) "- If I power the Backlights with my Backlight Tester, there still is no picture" Since there is no 12V that means you will not have 12V to run the T-CON board which means there will be no image on the screen, 12V is also used for the audio amplifiers so there will be no sound either.

2) You also indicated that you have 0V at the LED connector, and since power transformer TM1 (driven by MOSFET's QM1, QM2) is responsible for making the LED power supply Voltage (rectifier DM6, DM7), and the 12V (rectifier DM4).

3) Since PS-ON pin 3 never change state when turning TV on and off, that means the 12V/LED power supply will not be turn on, it is staying at <1V as you report. You will have to force on the power supply using the pull-up resistor to verify if the 12V & LED power supply are OK or not.

4) If you have shorted LED's then at least the backlights should flash on for seconds BEFORE the protection circuits kick in, but you never see the backlights even come on for seconds, correct?

5) You report the Vf of the LED as 89.30V, since they are dual-LED (2 LED's connected in series) the Vf will be around 6V if driven by over 100mA, but since your tester only puts out about 30mA that means the Vf of the LED will not be 6V, it will only about 5.6V, see spec sheet of the LG LED graph page 12.
So 5.6V @30mA x 16 LED's = 89.60V! make sense? Your tester shows 89.30V. What do you think?

I would find out why you do not have LED Voltage and no 12V first, make sense? You need to use logic ,the data, and some simple math and knowing how to read spec sheet to help you troubleshoot the problem, taking the panel apart is the last thing you will want to do. It is up to you as to which direction you want to go.

https://www.shopjimmy.com/insignia-1...-led-board.htm

[nomoresonys]

Re: Insignia NS-50d40SNA14not turning on

What nelic said was logical, could be 2 bad leds, could be a protection circuit shutting it down because of those leds too, I can strip down to leds to get the full picture of what I'm dealing with in an hour on most tvs at a leisurely pace, doesn't bother me at all.

[R_J]

Re: Insignia NS-50d40SNA14not turning on

How in the hell are you going to get the power supply to turn on without a power on signal. the F$%*& board is in STANDBY... IT IS OFF.. There is NO power ON, OR backlight ON signals from the main board!
Before you start ripping into the panel, find a couple 1k resistors and test the power supply. takes less than 2 minutes to test the power supply.

[nomoresonys]

Re: Insignia NS-50d40SNA14not turning on

Well OK, now we're getting someplace, unhook the backlights from powerboard and the cable from powerboard to mainboard and test that bich with the resistor!!!! AND by the way this should almost always be your first test when the voltages are not reading correctly with everything hooked up, so as to try to isolate/narrow down the problem.

[budm]

Re: Insignia NS-50d40SNA14not turning on

"3) Since PS-ON pin 3 never change state when turning TV on and off, that means the 12V/LED power supply will not be turn on, it is staying at <1V as you report. You will have to force on the power supply using the pull-up resistor to verify if the 12V & LED power supply are OK or not."
Yes I am the guy with the most post.

[budm]

Re: Insignia NS-50d40SNA14not turning on

how in the hell are you going to get the power supply to turn on without a power on signal. The f$%*& board is in standby... It is off.. There is no power on, or backlight on signals from the main board!
Before you start ripping into the panel, find a couple 1k resistors and test the power supply. Takes less than 2 minutes to test the power supply.

+1000

[budm]

Re: Insignia NS-50d40SNA14not turning on

"4) If you have shorted LED's then at least the backlights should flash on for seconds BEFORE the protection circuits kick in, but you never see the backlights even come on for seconds, correct?

[henryvrensburg]

Re: Insignia NS-50d40SNA14not turning on

Hi guys,

Sorry for the delay, was away for a few days.

I did everything you advised me in previous posts, getting 12V of pin 13 and 14 after shorting Pin 3 and 7, I also tested DM4, couldn't detect a short. I then decided to check the backlights. The sides of the panel were glued or double sided. I really did my best, was very careful, but managed to break the panel. I eventually got to the backlights, tested them with my Backlight Tester. 8 Banks with 4 LED's on each. Tested 22,4V on my Tester, all working. So I guess it must have been the Mainboard not switching on the Power Supply. (At least I have a spare set of Backlights now) I must say that I only saw the last 8 posts after I F$%*& up the panel.

Thank you for the help, you guys are great.

[budm]

Re: Insignia NS-50d40SNA14not turning on

Thanks for the follow-up. Big panel is not easy to handle.