How can i test a smd component used in a tv source Samsung PL51F4000 XZ0

I have a Samsung Plasma TV PL51F4000 XZ0 lcd that I suspect the integrated LTV-155E photo-coupler may be damaged. I'd like to help you figure out how I can test this component to see if it's good or not.

eletmoraes napisał(a):LTV-155E

There is a TLP155E from Toshiba on your photo.

eletmoraes napisał(a):I'd like to help you figure out how I can test this component to see if it's good or not.

Please build a simple test environment as shown below:

Post edited - all the content below has been changed!



For initial state (switch not pressed) there is normally a LOW (0V) level on output pin 5 - D1 (red) LED is switched ON and D2 (green) LED is switched OFF. When you press and hold the switch, output pin 5 changes to HIGH (12V) level - D1 (red) LED should be switched OFF and D2 (green) LED should be switched ON. When you release the switch, all the circuit should go back to the initial state (D1 on, D2 off).

Optocoupler is faulty if both D1 and D2 are switched ON or OFF at the same time.

You can also measure resistance between pins 4 and 5, and between pins 5 and 6. If any of this resistance is low the chip is bad. If both resistances is high (in kΩ or MΩ range) you should test the chip to the schematic like @Vogelek23 suggested.