Hello all. Working on a sharp LC-50LB370U. A few days ago, I turned the tv on and immediately left the room, came back in and tv was black. Turned it off then on and all good (didnt think much of it at the time) for about a week. Did the same thing again but stayed black this time. When turning on, the word "sharp" is dimmer than normal I think then tv goes black. I do have sound and do have a display with the flashlight test. I trided unplugging and also holding in the power button for 30 sec, no change. I opened the back up and the backlights do turn on to some extent for a moment then off. Proceeded to take voltage readings, I am trying to determine if I have a backlight issue or a PS issue. I took voltage readings at the PS LED connector with reference to chassis ground. Here are the readings:
Pin 1, V+, 1 wire, 65.6v, spike to 96.3v, back to 65.6v
Pin 4, V-, 1 wire, 17.9v, spikes to 39v for a split second then quickly drops to what appears to be 0v, back to 16.8v
Pin 9, V-, 2 wires, 17.9v, spikes to 39v for a split second then quickly drops to what appears to be 0v, back to 16.8v
Pin 12, V+, 2 wires, 65.7v, spike to 96.9v, back to 65.7v
Since I have voltage on the v-, I am getting a return voltage so the ICs seem to be working but not sure when it drops to 0v for a second. Only thing not able to isolate the 2 wire set on pin 9/12 without further disassembly. I also unpluggged the TV, unplugged the multiconductor cable to the main board, plugged tv in and no backlights came on. Any advice would be appreciated. Thank you in advance.
Pin 1, V+, 1 wire, 65.6v, spike to 96.3v, back to 65.6v
Pin 4, V-, 1 wire, 17.9v, spikes to 39v for a split second then quickly drops to what appears to be 0v, back to 16.8v
Pin 9, V-, 2 wires, 17.9v, spikes to 39v for a split second then quickly drops to what appears to be 0v, back to 16.8v
Pin 12, V+, 2 wires, 65.7v, spike to 96.9v, back to 65.7v
Since I have voltage on the v-, I am getting a return voltage so the ICs seem to be working but not sure when it drops to 0v for a second. Only thing not able to isolate the 2 wire set on pin 9/12 without further disassembly. I also unpluggged the TV, unplugged the multiconductor cable to the main board, plugged tv in and no backlights came on. Any advice would be appreciated. Thank you in advance.
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