do not have a standby light

Thank you very much for the reply, will check on this and update soon.

@jayeff I tried my multimeter on the standby reference point and both power boards are around 1 volt when connected to the wall. Out of curiosity, I removed the power board from the TV and disconnected the main board and what I’m assuming is the power connector for the backlight/LCD. With the power board plugged into the wall by itself like this, the voltage at the reference point was a perfect 13 volts! So it must be the backlight/LCD connector shorting it out and giving it low voltage. I’m afraid that if this is the case then the panel is not able to be saved?

I just confirmed that if I connect everything on the tv as usual except the large connector on the power supply (not the small connector between the power supply and the main board, this is the only other connection on the power supply) then plug the power supply into the wall, I get a red standby light, and am able to turn on the TV and hear the startup chime. Of course, the tv has no picture or back light because I disconnected that from the power supply intentionally. what could be causing this to short out?

@thill44

When you set it up so that you can start the TV and hear sound, try shining a flashlight at an angle close to the screen and check for images. They will be very faint so try this in a darkened room if possible.

If they are there then it may be the backlights.

Disconnect the power to the TV and then disconnect the backlight LED power cable where it connects into the CNL801 socket on the power board.

Using an Ohmmeter, check the resistance between the following pins on the backlight LED power cable plug

pins 1 & 3, 4 & 6, 7 & 9 and 10 & 12.

If you don't get a reading or it is a very high resistance reading reverse the meter leads and check again. By rights they should measure nearly all the same with the leads in one direction and then all the same with the leads reversed i.e. red on 3 and black on 1, red on 6 and black on 4 etc should all be the same and then with black on 3 and red on 1 etc should all be the same but most likely will be different (or should be) to the first set of measurements with the leads the other way.

This is just checking to see if there's a very low resistance path on one of the 4 LED backlight strips that may be dragging down the voltage on the power board.

Also check if there's a low resistance path between any of the pins in the LED power cable and an earth point (screwhead) in the TV just in case there's a short to earth on the strips

Want to make a late update as I was able to solve the problem. I found out that this TV had been showing signs of failing backlights before it failed, with what I would describe as a dim column on about a quarter of the TV. I was not able to measure the resistance as described above, but I decided to tear down the TV and check the backlights instead. Once I could get a look at them I immediately noticed that one of the 4 strips of backlights had burned and melted entirely inside of the tv, which was shorting the power supply and restricting the tv from turning on unless they were disconnected. So I unplugged that led strip and plugged the power supply back in and all of the other backlights immediately lit up like oldturkey03 mentioned they would. Since then I replaced the LED and the TV is repaired. Thank you all for helping me diagnose the issue.