Board problem not powering - HP Compaq Motherboard

If you have checked and confirmed that the voltage at the PS_ON pin does not change when hitting the power button, it is possible that the main board (756TXBCB2K013) is the faulty component. The main board is responsible for sending the signal to turn on the power supply board (ADTVA2419XYG). You may want to try disconnecting the main board from the power supply board and then pressing the power button. If the voltage at the PS_ON pin changes, then it confirms that the main board is faulty. If there is still no change in voltage, then it is possible that the power supply board is faulty. Alternatively, you can also try checking the capacitors on both boards for any signs of bulging or leaking, as faulty capacitors can sometimes cause issues with power supply.

Bad main

Hi Mike,
I appreciate your DIY effort. Were you sure of power supply board being bad? From what you have mentioned, the main board seems to be bad. Because if the power board is good, the set will not power on unless it receives the power on command from the main board.
One more thing, in most of the Samsung sets on disconnecting power supply and main board, If you get the backlights, power supply board is OK and the main board is bad. Please try this. Good luck.

I thinks you need use a new power board instead of the old power board ,you can have a look https://www.abctay.com ,you may find what you need.

Sustain board fault. If you wish to get some details; check the site linked here. Pull up older posts. http://electronicshelponline.blogspot.com/

Hi Pam,
For a TV to come on, the power board has to send 'stand by or SB5V or 3.5V ' to the main board. On your pressing power on button on remote control, the main board sends power on command to the power board which in turn produces all the necessary supplies to run the TV. If the main board does not respond to your TV on command, the TV will not work. So It is not the power board which is responsible for not powering on of a TV every time. A voltage investigation before changing boards is always helpful. I hope it helps.

The main board is defective the power on command originates from the main board and thats what gives the signal to start powering up the set. Replacing the main board should solve the issue. You can get the main board from www.tvcircuitboards.com

The power supply board could very well be defective. I would also check the Zsus board and the Xsus boards. If either of these boards fail it could also cause the power supply board to fail.
You can unplug the connectors to the zsus board at the power supply and try to turn the set on. If it does turn on, the power supply board is ok. If not, the power supply is bad. If the power supply board is ok, undo the plug connectors that power the Xsus board and hook up the plug connectors to the Zsus board. Turn the set an and see if it stays on or shuts down. Part numbers should be on the boards. Zenith is really LG Corp. Their customer support number is 1800-243-0000.
Hope this helps,
Steve

Without the correct meters and equipment it can get exspensive replacing boards however it almost has to be located on the power filter or the power board. I would suggest the power board over the power filter.