Hello,
I have a 70" sharp tv, a bit of history about this tv, the place I work bought it new, it sat in storage for over a year, when it was unboxed it was dead. Flashing center light 1 fast 1 slow. No warranty left on it so they gave it to me instead of scraping it.
I did the Input + volume down to get it in service mode and reset the lamp error - this worked a few times untill the tv failed to turn on even for the service mode.
I want to learn about fixing tv's and found this to be a great opportunity for such.
I took the back cover off, downloaded the service manual - popped the front screen off and tested all the LED's - I was expecting a few mini light bulbs... and almost wet meself when I saw over 400 LED's - I used a 48VDC source to test 5 or so at a time using the TP's on the strips. they all lit up nicely.
At the moment with everything plugged in as normal - the TV will flash the LED's on for about .5 seconds and then kick off the PSU giving the 1 fast 1 slow flash. I have tried all the button tricks of volume + channel ... pwr and so on. Same results.
I then disconnected the cable between the PSU and the main board - jumped the PS-ON to BU5V and PNL-POW (so the 3 connect together) the PSU comes to life - no LED action from doing this.
There is a PIN labled OFL which I don't know what it means and would like to understand it's function. when the PSU is on, there is 700+ AC volts on the primary side which got me all excited. from my random testing there is no pwr going to the transformers for the LED's, I can't find what kicks on the transistors for them. I get no voltage from the STB pin at any point.
If the main board can kick it on for it's testing phase, surely I should be able to.
I am learning about transistors and diodes and all the other fun stuff as I go. I tested the transistors and am confident they are good. (un-Soldered them and tested the different legs based on schematic found for the model)
Now I must confess that I damaged the front panel when taking it off - who knew it was a bad idea to do so with the tv upright. I have disconnected the 2 big ribbon cables that connect to the TCON (if thats what it's called) board for all of my testing. I realize this TV will never be used again, and to be honest it's far to big for any normal house. But it does offer a great test lab to learn from.
So my question is - how to force the backlights on - i get all the right voltages based on the pins including PNL 12V on pins 1 + 2 but whatever tells the lights to come to life has been eluding me.
will attach some pics in a short while.
I have a 70" sharp tv, a bit of history about this tv, the place I work bought it new, it sat in storage for over a year, when it was unboxed it was dead. Flashing center light 1 fast 1 slow. No warranty left on it so they gave it to me instead of scraping it.
I did the Input + volume down to get it in service mode and reset the lamp error - this worked a few times untill the tv failed to turn on even for the service mode.
I want to learn about fixing tv's and found this to be a great opportunity for such.
I took the back cover off, downloaded the service manual - popped the front screen off and tested all the LED's - I was expecting a few mini light bulbs... and almost wet meself when I saw over 400 LED's - I used a 48VDC source to test 5 or so at a time using the TP's on the strips. they all lit up nicely.
At the moment with everything plugged in as normal - the TV will flash the LED's on for about .5 seconds and then kick off the PSU giving the 1 fast 1 slow flash. I have tried all the button tricks of volume + channel ... pwr and so on. Same results.
I then disconnected the cable between the PSU and the main board - jumped the PS-ON to BU5V and PNL-POW (so the 3 connect together) the PSU comes to life - no LED action from doing this.
There is a PIN labled OFL which I don't know what it means and would like to understand it's function. when the PSU is on, there is 700+ AC volts on the primary side which got me all excited. from my random testing there is no pwr going to the transformers for the LED's, I can't find what kicks on the transistors for them. I get no voltage from the STB pin at any point.
If the main board can kick it on for it's testing phase, surely I should be able to.
I am learning about transistors and diodes and all the other fun stuff as I go. I tested the transistors and am confident they are good. (un-Soldered them and tested the different legs based on schematic found for the model)
Now I must confess that I damaged the front panel when taking it off - who knew it was a bad idea to do so with the tv upright. I have disconnected the 2 big ribbon cables that connect to the TCON (if thats what it's called) board for all of my testing. I realize this TV will never be used again, and to be honest it's far to big for any normal house. But it does offer a great test lab to learn from.
So my question is - how to force the backlights on - i get all the right voltages based on the pins including PNL 12V on pins 1 + 2 but whatever tells the lights to come to life has been eluding me.
will attach some pics in a short while.
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