Hi guys
Got a Toshiba 40L3433DG LED TV with no backlight
This has a Vestel 17IPS20 PSU
When the TV starts up I get 125V between the output to the LEDs and chassis ground, this then goes up to 190V or so then gradually comes back down to 125V but no backlights
However when I measure between LED +ve and -ve leads (as opposed to +ve and chassis ground) I get no voltage which would suggest to me that the LED driver chip is open circuit between the LED return and ground which connects via an internal FET I think.
So I then connected an LED back light tester and the back lights do actually work (I also get a picture on screen) but the back light tester voltage goes all over the place and the LED back lights brightness flickers especially when the voltage jumps down. That would suggest to me there is a problem with the LED strips somewhere. I've uploaded a video of this but it's not easy to see the back light flicker, just the tester voltage behaving strangely. Basically the backlights come on at about 140V then the voltage keeps climbing to over 200V, the lights flicker and hte voltage jumps back down to about 125V and the process repeats either immediately or after several seconds of stable voltage.
I've not seen this before. Can anyone with more experience of these testers advise on where the problem is? Driver or LED chain?
video
https://youtu.be/CR7BEJPoxTI
Got a Toshiba 40L3433DG LED TV with no backlight
This has a Vestel 17IPS20 PSU
When the TV starts up I get 125V between the output to the LEDs and chassis ground, this then goes up to 190V or so then gradually comes back down to 125V but no backlights
However when I measure between LED +ve and -ve leads (as opposed to +ve and chassis ground) I get no voltage which would suggest to me that the LED driver chip is open circuit between the LED return and ground which connects via an internal FET I think.
So I then connected an LED back light tester and the back lights do actually work (I also get a picture on screen) but the back light tester voltage goes all over the place and the LED back lights brightness flickers especially when the voltage jumps down. That would suggest to me there is a problem with the LED strips somewhere. I've uploaded a video of this but it's not easy to see the back light flicker, just the tester voltage behaving strangely. Basically the backlights come on at about 140V then the voltage keeps climbing to over 200V, the lights flicker and hte voltage jumps back down to about 125V and the process repeats either immediately or after several seconds of stable voltage.
I've not seen this before. Can anyone with more experience of these testers advise on where the problem is? Driver or LED chain?
video
https://youtu.be/CR7BEJPoxTI
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