I have had this TV for nearly 6 years from new. It has been connected to a smart powerboard the whole time so the power to the TV is turned off when the AV Receiver turns off. Was working fine one day and then the following day wouldn't power on. The red standby LED lights up but when I press power on the remote or manually the red LED turns off after a second or so and then comes straight back on. I've connected the TV to a power meter and the TV is only drawing ~1W even after the power button is pressed so not much is happening.
I took off the back and was hoping to find an obvious fault but everything looks pristine, fuses have continuity and none of the caps looked domed or have leaked. Testing the power board voltages on standby has the 13.2V rails oscillating between 11.65 and 11.85 approx every 2 seconds. The LED+ on the black and white leads are also oscillating between 95.9 and 96.1 at the same frequency. Pressing the power button briefly drops the 13.2V rail to 5V but goes back to the previous value. The green led on the power board doesn't light up.
I tried reflowing the mainboard in the oven without any change. I ended up ordering a replacement mainboard but unfortunately it behaves the same.
I followed the instructions found on this link:
https://masterelectronicsrepair.blog...wer-board.html
Applying 3V externally to PWR_ON and DRV_ON makes the LED backlight blink on and off and the green LED will start blinking. The voltages with the jig connected oscillate between 11.8 to 13.6V but dips briefly to 10.5V when the LEDs flash. If I also add the 12V 21W lightbulb as per the link to any of the 13.2V rails the LED backlight stops blinking and the bulb pulsates at a regular interval (see video). The 13.2V rail drops down to between 0 and 3V with the pulsation of the light. The light bulb behaves this way whether or not the 3V is applied to the PWR_ON and DRV_ON connectors. There is a faint ticking coming from the board on standby that gets louder when the light bulb is connected and is the same frequency as the light pulsation.
I'm guessing something has failed on the powerboard but don't know where to start. Not keen on getting another power board as they are expensive and also mindful they will be the same age and might be about to fail the same way. Any advice for a noob would be greatly appreciated.
I took off the back and was hoping to find an obvious fault but everything looks pristine, fuses have continuity and none of the caps looked domed or have leaked. Testing the power board voltages on standby has the 13.2V rails oscillating between 11.65 and 11.85 approx every 2 seconds. The LED+ on the black and white leads are also oscillating between 95.9 and 96.1 at the same frequency. Pressing the power button briefly drops the 13.2V rail to 5V but goes back to the previous value. The green led on the power board doesn't light up.
I tried reflowing the mainboard in the oven without any change. I ended up ordering a replacement mainboard but unfortunately it behaves the same.
I followed the instructions found on this link:
https://masterelectronicsrepair.blog...wer-board.html
Applying 3V externally to PWR_ON and DRV_ON makes the LED backlight blink on and off and the green LED will start blinking. The voltages with the jig connected oscillate between 11.8 to 13.6V but dips briefly to 10.5V when the LEDs flash. If I also add the 12V 21W lightbulb as per the link to any of the 13.2V rails the LED backlight stops blinking and the bulb pulsates at a regular interval (see video). The 13.2V rail drops down to between 0 and 3V with the pulsation of the light. The light bulb behaves this way whether or not the 3V is applied to the PWR_ON and DRV_ON connectors. There is a faint ticking coming from the board on standby that gets louder when the light bulb is connected and is the same frequency as the light pulsation.
I'm guessing something has failed on the powerboard but don't know where to start. Not keen on getting another power board as they are expensive and also mindful they will be the same age and might be about to fail the same way. Any advice for a noob would be greatly appreciated.
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