1-894-595-12 - main board
XBR-55X900C - model
Working on this Sony. Starts to turn on, animated logo runs for maybe 2-4 seconds, freezes, tv turns off. Sometimes relay clicks off then back on. Cycles indefinitely.
Nothing on board getting abnormally hot.
5v on USB will turn off with cycle as expected.
power on signal between PSU and main board will drop from 3.55 to 3.49 (odd drop in my opinion). Not sure if significant. I would think 3v or 0V. Holding it at 3.55 with external supply changes nothing.
Anyone know what actually controls the main board into the on/running state? There is a PIC16 on the board, but i cant find anything in the way of documentation as to what it is doing. It has 2 transistors connected to it. I moved both out of circuit with no change in condition.
I know others with this exact condition have replaced the main board and that worked, but if anyone has any ideas as to what may be the cause, i would much rather repair and document the failure vs just putting a board in it.
XBR-55X900C - model
Working on this Sony. Starts to turn on, animated logo runs for maybe 2-4 seconds, freezes, tv turns off. Sometimes relay clicks off then back on. Cycles indefinitely.
Nothing on board getting abnormally hot.
5v on USB will turn off with cycle as expected.
power on signal between PSU and main board will drop from 3.55 to 3.49 (odd drop in my opinion). Not sure if significant. I would think 3v or 0V. Holding it at 3.55 with external supply changes nothing.
Anyone know what actually controls the main board into the on/running state? There is a PIC16 on the board, but i cant find anything in the way of documentation as to what it is doing. It has 2 transistors connected to it. I moved both out of circuit with no change in condition.
I know others with this exact condition have replaced the main board and that worked, but if anyone has any ideas as to what may be the cause, i would much rather repair and document the failure vs just putting a board in it.
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