Hello good people, I have another unit here which is giving me problems. Upon plugging the unit it, after a few seconds the front LED will start blinking 3 times in a row and repeating indefinitely. No image or sound.
The first thing I checked was the backlight. It's a single vertical strip on one side of the panel which has 8 groups of 7 LEDs. (Part #V500D2-LS1-TREM3) I used a backlight tester and each group lit up without issue.
The standby 5.3V is good, the 16V and 24V from the PSU board both come up for a few seconds while the TV_SUB_ON signal is high. Both 16V and 24V stay on when forced. I also tried to force the backlight on but the LED driver board keeps resetting - it comes up to about 55V and resets about once a second making the backlight flash repeatedly. It requires a PWM signal which I did not provide, which is possible why it would not stay on?
The LED driver board never receives a BL_ON signal from the A board which would make sense given that the PNL12V output never turns on. For some reason the A board is unhappy and doesn't want to enable the 12V regulator. I noticed that when the A board receives the 16V input, an ERR pin goes high at about the same time, then the TV_SUB_ON signal goes low and the power board turns off.
While troubleshooting I stumbled across this Panasonic "Technical guide" which references this model. It's kind of like a watered down service manual as it features somewhat high level schematics but still a lot of useful info: https://service.panasonic.ca/pcs/EXT...uide_Final.pdf
Here's the power on procedure from the technical guide and it shows how far mine gets.
Additionally here's the P and A board "schematic"
I was able to find some of the IC's that are supposed to be turned on by the F15V signal:
IC Expected Measured
IC8704 5V 5V
IC8705 3.3V 3.3V
IC8100 1.1V 0V
IC8101 1.5V 0V
IC5704 1.8V 0.6V
IC8715 3.3V Can't locate
IC5702 1.2V Can't locate
The first thing I checked was the backlight. It's a single vertical strip on one side of the panel which has 8 groups of 7 LEDs. (Part #V500D2-LS1-TREM3) I used a backlight tester and each group lit up without issue.
The standby 5.3V is good, the 16V and 24V from the PSU board both come up for a few seconds while the TV_SUB_ON signal is high. Both 16V and 24V stay on when forced. I also tried to force the backlight on but the LED driver board keeps resetting - it comes up to about 55V and resets about once a second making the backlight flash repeatedly. It requires a PWM signal which I did not provide, which is possible why it would not stay on?
The LED driver board never receives a BL_ON signal from the A board which would make sense given that the PNL12V output never turns on. For some reason the A board is unhappy and doesn't want to enable the 12V regulator. I noticed that when the A board receives the 16V input, an ERR pin goes high at about the same time, then the TV_SUB_ON signal goes low and the power board turns off.
While troubleshooting I stumbled across this Panasonic "Technical guide" which references this model. It's kind of like a watered down service manual as it features somewhat high level schematics but still a lot of useful info: https://service.panasonic.ca/pcs/EXT...uide_Final.pdf
Here's the power on procedure from the technical guide and it shows how far mine gets.
Additionally here's the P and A board "schematic"
I was able to find some of the IC's that are supposed to be turned on by the F15V signal:
IC Expected Measured
IC8704 5V 5V
IC8705 3.3V 3.3V
IC8100 1.1V 0V
IC8101 1.5V 0V
IC5704 1.8V 0.6V
IC8715 3.3V Can't locate
IC5702 1.2V Can't locate
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