Re: Sharp LC 60LE655U 2 long flashes + 2 short flashes
Thanks attainteddragon and R_J.
The diode tested fine after I lifted one leg. It was indeed a IN4148.
I still think the problem is in that general area of the board. The opto PC7904 has 0.6V on its diode side which means a very small current is flowing through it.
If the opto diode current increases,
--> the transistor side of the opto would see a drop in resistance,
--> the Q7902 transistor would turn on
--> Vcc would reach IC7601
and thus the UR13.2 voltage would rise to its expected level.
To test, I momentarily shunted the opto transistor with a 11k resistor and got a voltage on UR13.2 ( I have 11 test LEDs in series on the UR pin that lit up)
Does this analysis make sense? What can I test next?
Thanks attainteddragon and R_J.
The diode tested fine after I lifted one leg. It was indeed a IN4148.
I still think the problem is in that general area of the board. The opto PC7904 has 0.6V on its diode side which means a very small current is flowing through it.
If the opto diode current increases,
--> the transistor side of the opto would see a drop in resistance,
--> the Q7902 transistor would turn on
--> Vcc would reach IC7601
and thus the UR13.2 voltage would rise to its expected level.
To test, I momentarily shunted the opto transistor with a 11k resistor and got a voltage on UR13.2 ( I have 11 test LEDs in series on the UR pin that lit up)
Does this analysis make sense? What can I test next?
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