Hi guys, sorry to have a few threads all on the go at once right now. I have a spate of Toshiba TVs with back light problems - but this is a general LED question really.
So I have on the bench now a Toshiba 40HL933G
It has four chains of LEDs in parallel.
The fault is the Power supply comes up OK (5V 12V 24V)
PS_ON goes to 3.3V
INV_ON_OFF goes to 3.3V
BRIGHT_ADJ goes to 3.3V
The back lights flash on very briefly and go out. BRIGHT_ADJ goes to 2.9V
Pressing the standby button repeats the process
When I test the LED chains with a back light tester they all illuminate but I see I have three chains with almost the same voltage 78.4V - 78.7V and the other chain is 84.9V
I would have expected they would all be the same or at least much closer than that.
Would such a large voltage difference on one chain cause the LED driver IC (in this case SSL110SN) to detect a fault condition on the LEDs and shut down hence the back lights flash briefly?
Thanks
Rich
So I have on the bench now a Toshiba 40HL933G
It has four chains of LEDs in parallel.
The fault is the Power supply comes up OK (5V 12V 24V)
PS_ON goes to 3.3V
INV_ON_OFF goes to 3.3V
BRIGHT_ADJ goes to 3.3V
The back lights flash on very briefly and go out. BRIGHT_ADJ goes to 2.9V
Pressing the standby button repeats the process
When I test the LED chains with a back light tester they all illuminate but I see I have three chains with almost the same voltage 78.4V - 78.7V and the other chain is 84.9V
I would have expected they would all be the same or at least much closer than that.
Would such a large voltage difference on one chain cause the LED driver IC (in this case SSL110SN) to detect a fault condition on the LEDs and shut down hence the back lights flash briefly?
Thanks
Rich
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