Hi Guys,
This tv came in with a back light that used to switch off intermittently. After measuring around the PWM IC and i can confirm that i made NO SHORT CIRCUIT the LED's went quite dark and stayed like that. They barely shine!!!
This is the readings i have,
LED+ = 38.6V
LED+ = 38.6V
LED+= 38.6V
LED+= 38.6V
LED+= 38.6V
LED+= 38.6V
LED6- = 1.62V
LED5- = 1.60V
LED4- = 1.61V
LED3- = 1.62V
LED2- = 1.62V
LED1- = 1.63V
also the Adjust pin is 5.1V
and BL-ON = 1.6V
If i use a backlight tester and they all come on, not to say that they are not intermittent but the LED tester indicates a voltage of 41V on all six circuits and there is a blueish light emanating from the rear stand offs. I guess being biased slightly.
Previously before these back lights went from intermittent off to permanently dim i did take off the LCD display and put power to see that all LED's came on nice n bright and then after a few minutes they just faded off. I then started fault finding around the PWM and that's what caused the failure of output voltage.
Just to give you an idea i disconnected one of the LED- leads and put my Fluke meter in series to monitor the current and when i powered up the TV the backlights flashed and went off immediately. As if it did not like the fluke in series and i cant understand why.
My question is, is it the back lights or the power supply?
This tv came in with a back light that used to switch off intermittently. After measuring around the PWM IC and i can confirm that i made NO SHORT CIRCUIT the LED's went quite dark and stayed like that. They barely shine!!!
This is the readings i have,
LED+ = 38.6V
LED+ = 38.6V
LED+= 38.6V
LED+= 38.6V
LED+= 38.6V
LED+= 38.6V
LED6- = 1.62V
LED5- = 1.60V
LED4- = 1.61V
LED3- = 1.62V
LED2- = 1.62V
LED1- = 1.63V
also the Adjust pin is 5.1V
and BL-ON = 1.6V
If i use a backlight tester and they all come on, not to say that they are not intermittent but the LED tester indicates a voltage of 41V on all six circuits and there is a blueish light emanating from the rear stand offs. I guess being biased slightly.
Previously before these back lights went from intermittent off to permanently dim i did take off the LCD display and put power to see that all LED's came on nice n bright and then after a few minutes they just faded off. I then started fault finding around the PWM and that's what caused the failure of output voltage.
Just to give you an idea i disconnected one of the LED- leads and put my Fluke meter in series to monitor the current and when i powered up the TV the backlights flashed and went off immediately. As if it did not like the fluke in series and i cant understand why.
My question is, is it the back lights or the power supply?
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