insignia ns-48 no backlights

[robert phelps]

I have a insignia ns-48d510na15 that the backlights will not come on. i have an led tester and the leds work and pull 163 volts. on the psu for led+ when powered on goes to 195 volts and within a second to less then 1 volt. the power led flashes 6 times which what i have found out is backligh problem. there are several listing on the psu to the logic board that i dont understand... connector label of pwm3 3de 3ds and sw .. the best i can tell my stb voltage is 3.5 volts with set on but its 53.3 with set off . what do i need to look at?

[robert phelps]

Re: insignia ns-48 no backlights

also when you power the set on up close to the psu you can hear a small whine for a few seconds then it stops

[maxvalutech]

Re: insignia ns-48 no backlights

Pictures Robert??

[budm]

Re: insignia ns-48 no backlights

"i have an led tester and the leds work and pull 163 volts. on the psu for led+ when powered on goes to 195 volts and within a second to less then 1 volt. " That sound like there is no current return on the Cathode side for the LED string, that is why you get 195V due to no load.

[robert phelps]

Re: insignia ns-48 no backlights

Here are pic

[budm]

Re: insignia ns-48 no backlights

Need pictures the whole backside showing all the boards and how they are connected together.
It only use one string of LED.
LED connector in place and probe at the pins of the connector on the board, report the Voltage reading between chassis GND and the Black wire of the LED, Gnd and White wire of the LED, you muat leave the probes on the test point and then turn on the TV otherwise you may not catch how high the Voltage goes up to before it goes into shutdown.

[robert phelps]

Re: insignia ns-48 no backlights

Here are pics of underside of psu and logic boards. My first post stated that led+ goes up to 195 volts and then shuts down

[budm]

Re: insignia ns-48 no backlights

Please do the test as requested in post 6. You only report the feeding wire Voltage, you did not report the return wire Voltage with ref to the chassis GND.
"LED connector in place and probe at the pins of the connector on the board, report the Voltage reading between chassis GND and the Black wire of the LED, Gnd and White wire of the LED, you must leave the probes on the test point and then turn on the TV otherwise you may not catch how high the Voltage goes up to before it goes into shutdown."

[robert phelps]

Re: insignia ns-48 no backlights

Black. Led+ goes to 195 and shuts down. White. L ed- .5 is all it shows. That's .5, these voltages are the same with and without the leds hooked up

[budm]

Re: insignia ns-48 no backlights

Well, you have open circuit because the LED - only show 0.5V so the output went up to 195V due to no load, recheck the connection between the male pins of the LED connector on the power supply board all the way to the LED strip are OK.

[anthonya661]

Re: insignia ns-48 no backlights

I have the same set turned out bad led's

[robert phelps]

Re: insignia ns-48 no backlights

I can use my led tester from the connector and all the leds light, I have checked each strip themselves and all is good. I can light up the leds by touching the pins on the psu at the connector for the leds, not bad cable or leds.

[budm]

Re: insignia ns-48 no backlights

I do not know what to tell you, you 195V feeding into one wire of the LED string and the return wire only shows 0.5V, you also get 195V with or without LED connector in place. Measurement error or wrong DATA some where.
"the best i can tell my stb voltage is 3.5 volts with set on but its 53.3 with set off "
Do you mean 53.3mV at the STB pin? It is the same as PS-ON, so if you actually have 55.3V you will see nice smoke coming out of your TV.
So are you 100% sure that you read the meter correctly?
SW = BL-ON signal
PWM = Pulse Width Modulation Dimming control signal.
You have 195V across the whole set of the LED string but the string only need about 163V (it will be higher at 300mA) to light up at about 30~50mA of current so no way it will not even light for seconds. You have open circuit some where.
How many LEDs are there total?

[robert phelps]

Re: insignia ns-48 no backlights

There are 10 strips but I don'tremember how many was on each strip, thinking it was 6 leds per strip, so 60 total

[robert phelps]

Re: insignia ns-48 no backlights

I hooked up my led tester to the led leads, DVD player to hdmi and watched toy Story for 20 minutes on this set, what in the psu could be making it shut down the leds?

[budm]

Re: insignia ns-48 no backlights

It will go into shutdown when over Voltage occurs (I.E. 195V) when there is no load, it also shutdown if over current is detected.
You can use 100 Ohms 2W resistor between GND and the LED - pin to see if the LED will come on at all.

[axlmastr]

Re: insignia ns-48 no backlights

I have the same model TV to look at. The symptom is no backlight. If looking at the screen from the right angle or using a flashlight I see the image and of course sound works. I remember repairing earlier backlight issues with a CCFL tube or inverter, but haven't done and LED. I was reading through this and checked my voltages as requested here by BudM a long time well respected electronics guru here and though to post and see what he would say.

Black wire at power on rises up to 238-245VDC and bounces between +238 & 245 consistently. White wire at power on rises up to -68-73VDC and again bounces between those two numbers consistently. When powering off the numbers slowly count down to below +5 or -5VDC respectively. I see there some caps from Chang and Capxon used on this board the doesn't make me happy since I've replaced hundreds of those brands over the years.

Where to look? New LED strips? 10 total needed.