Sony XBR-55X900C on for a few seconds then off.

[itelite]

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.

[brucetv]

Re: Sony XBR-55X900C on for a few seconds then off.

I had this model in several times and after every attempt to do a component level repair on these main boards I have failed including the 65" main board version. XBR stands for Xtra Brain Rack because the Main boards are overkill and usually have decent chipsets making them harder to diagnose. By the time I got numbers off components, checked their specs, run traces, and start probing I slowly lose hope. If it's your personal Tv and you have plenty of time on your hands go for it and please let us know what you found. If we have a customer waiting then a fresh main board with a new firmware installed when we get then new main then it usually ends the boot looping power cycling, installs the new firmware and turns off then on and instructs you to take out the usb when firmware install is finished. Very nice picture too.

[itelite]

Re: Sony XBR-55X900C on for a few seconds then off.

Got a new board. now the tv powers on. Nothing on screen at first, plays some weird music for a while. does nothing then goes to sleep (?)

Put newest firmware on a usb drive and put it in. blinked green and amber for a while. changed to slowly pulling white and oddly started cycling through colors on the screen. left it alone for 20 minutes at least. went to sleep again.

hit power button, back to color cycle.

Never an indication on screen of a firmware update happening.

I dont do a ton of sonys, is a human sacrifice required?

[itelite]

Re: Sony XBR-55X900C on for a few seconds then off.

Nevermind. Got it.

If at first you dont succeed, do the exact same thing again, and for some reason it will work the second time.