Re: Insignia NS-55D420NA16 Backlight Problem
OK, there are two wires for the LED connector.
Red wire is the Anode pin of the LED strip
White wire is the Cathode return of the LED strip.
So you are getting about 190V on the red wire and 0V on the wire?
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Re: Insignia NS-55D420NA16 Backlight Problem
yes. the 56v was to chassis ground. my meter doesnt have min/max so i may not be getting an acurate reading since the voltage spikes and drops so quickly.
i retested again using the connector ground and it spikes at around 190 volts.Leave a comment:
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Re: Insignia NS-55D420NA16 Backlight Problem
there are labels for more than 10 pins but the connector only has 10 pins and the plug only has 10 wires. the voltages are listed from left to right from the plug side.
i retested again and the output to the LEDs hits like 190ish volts for a split second when the backlights come on.
Thanks!Leave a comment:
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Re: Insignia NS-55D420NA16 Backlight Problem
There looks like at least 15 pins on the connector but you have only listed 10 of them.
Does your multimeter have min/max function to check the led voltage which spikes to a maximum and then drops quickly. According to the print on the circuit board it should be around 200V to drive the leds.Last edited by dick_barton; 06-19-2018, 06:09 AM.Leave a comment:
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Re: Insignia NS-55D420NA16 Backlight Problem
Hi,
See below for the voltages on the 10 pin connector:
Gnd: 0v
Gnd: 0v
Pwm12: 4.8v
Sw: 2.8v
12v: 11.9v
12v: 11.9v
Stb: 3.3v
Gnd: 0v
16v: 18.9v
16v: 18.9v
For the led connector it peaks at 56 volts for the half a second the backlight turns on then drops to .9 volts.
Also I took a video of the backlight turning on and it appears only one side is working. Would that indicate bad LEDs??
https://youtu.be/84RGStWo4bMLeave a comment:
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Re: Insignia NS-55D420NA16 Backlight Problem
Can you list the voltages against the pin names in the red box.
What voltage do you have on the connector in the green box when you power up.Attached FilesLeave a comment:
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Re: Insignia NS-55D420NA16 Backlight Problem
as an update, the inside of the TV looks very similar to this one i found on youtube.Attached FilesLeave a comment:
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Insignia NS-55D420NA16 Backlight Problem
Hi All,
Did a little bit of searching but i couldnt find anyone with a model that looks like mine so figured i'd make a post to try to get some help troubleshooting. We have an Insignia (hisense) 55" LED with a backlight problem. when i turn the TV on the backlights come on for about a second but then immediately shut off. once the backlights are off the panel is still working and i have sound but no backlights. I opened up the TV this weekend and tested the output from the power supply board. I get voltage coming out for the second the backlights are on but then nothing once they shut off. im suspecting something with the power supply but not really sure how to validate this.
I didnt take pictures of everything but i do have pictures of the power supply board. There was also a t-con board and main board inside this tv.
Open to any suggestions on what i can test to try to get this back up and running.
Thanks!
PeterAttached Files -
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TCL 75S421
PSU BOARD: 40-L402H8-PWD1CG
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