Question about Televison & Video
I have a AKAI LCD2701 tv that won't turn on.
The RED LED is lit on the front but I get no response from the remote or power buttons on the side.
I am a EE so I have done a little debug but need some help from someone who knows LCD TV circuits.
There are three boards behind the case. One is clearly the AC/DC power supply board, one seems to be the TV tuner card and one looks to be the master controller. I have +5.0 volts running to the master controller and to all the switches (probably why the RED LED works). The other labeled power outputs (+12v & +24v) from the power board are sitting at GND. I assume this is because the unit is in "standby" waiting for the controller board to signal a power on condition. There is a 27Mhz crystal that probably feeds whatever is under the adjacent heat sink (ASIC or FPGA) on the controller board and that seems to be running okay according to my scope when the AC switch (near the plug entrance) is on. My guess is that the controller for some reason is not enabling the power on condition. Here are a couple of my questions:
1) Any safety features I can look for that would keep the controller from turning on the power. I am thinking of thermal protection, under voltage conditions, etc.
2) There is a connector from the controller board to the power board that has SB+5.0, GND and SB. The first one is sitting at +5volts, the later two at GND. I was thinking of shorting the +5.0 to the SB with a 10k resistor to see if I could force the power supply on since my guess is that it is the power on signal. I am hesistant since I don't have a schematic and only guessing.
Thanks in advance.
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Posted on Jan 02, 2017
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