Not turning on, is dead

Yes this sounds like a power board related problem. Either replace the capacitors that may look like they are bulging (the tops) or have leaked ; or replace the power board with another unit -- used they are around only $30

1. When the TV powered up, please measure the 24V, 12V & 5V are there, if one voltage is missing, you may have a defective power supply.

2. If the power supply lost the 24V source, you may unplug the power supply connector on both the inverter board, then power it up, if you got the 24V back, you do have a defective inverter board, you may unplug them one at a time to locate the bad one.

3. If the power supply & inverters are good, you may have a defective main board. The common problem on the main board is that a voltage regulator is bad, you may use your millimeter to measure them 1 x 1. The out put voltage (on the heat sync) should be 1.25V + the control voltage (Pin 1), for example: if the control pin voltage is 0, the output voltage should be 1.25V, if the control voltage is 2.05V, the output voltage should be 3.3V, if one of them is out of range, replace it, you may find the part from Digikey Co. The part number printed on the regulator is AMC1117.


Good luck!

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yes after to the fuse you must have a reading of 120vac if none the fuse get busted. if the 120v is present then it will goes through the rectifier bridge diode and primary capacitor of the power supply board to have an stand by voltage at the power supply board. when you press the power button it will send signal voltage coming from the main board to turn on the power supply board. the you will need to get an output voltage at the power supply board of 5v dc, 12v-16vdc and 24v to turn on the all the circuit, the main board sound amplifier and the inverter board for screen back light.if you can get those supply the tv unit will not turn on.

tried to disconnected the 24v supply connectors going to the power inverter board which may the cause of voltage drop. after you disconnect then if still no output 24v dc coming from the power supply board the cause will be bad power supply board. check for an open resistance or bad regulators going to the 24vdc out. by the way you should connect all the connectors going to the main board to turn on the processor and the inv_on voltage going to the inverter board.

Sounds like the circuit board is a good suspect.
Sometimes a resoldering of compoment leads will fix things.
You can also replace the circuit traces with individual wires

Sounds like you have already done a good trouble shoot, so I hope this info helps you get back in action

First thing to do is measure the output voltages of the power board. You're looking for the one that provides standby power, usually +5V or +3.4 V and in some rare cases other voltages.

Don't know what it is for your TV, but it will sure be available on the power board if you see the red LED there.

Next you look to see if upon pressing power the main board signals to the power board to turn itself fully on, i.e. start generating the rest of the supply voltages.

There's a pin on the power board's connectors that is labelled "PS_ON" or just "ON" or something similar.

It should raise to +3V or so when you press the ON button.

For an example of a simple power board see this:
http://blog.coppelltvrepair.com/2010/09/how-to-test-power-supply-r0804-0901.html

If you do not receive that signal then the problem is in the main board.
if you receive that signal, but the power board does not generate the additional voltages that it outputs to the other boards then the problem is in there.
And if it wakes up and provides those voltages but the TV is still dead then the problem is in the main board, which usually needs to be replaced.

Hope this helps. If it does do not forget to rate it :-)

if you need more help - supposedly paid though - feel free to contact us.

www.coppelltvrepair.com

Ur main Tuner board is dead also,must be changed to get this tv fix,because the power board when it had bad caps,it send to much voltage it also kill the Tuner board.This happen in some cases,it not only the power board it dead,but their over flow of voltages kill the Tuner board too.

The buzzing sound your hearing is a transformer that is producing 24v ac current to the main control Board, this is what controls the unit. you can check for 24v to the main board by removing the front panel access door and finding the safty shut off switch that the door touches, and depress it or tape it so you can test for voltage.. if you have 24v ac from the transformer next test at the board, if you have voltage there you may have board issues??? check the fuse on the board, make shure all connections are good... if you do not have 24v to the board your transformer is bad, have a hvac technician service this, don't attenmpt to do this yourself if you don't have experince, you could destroy your cont. board.....
hope this helps

power supllay