My Samsung 60" smart tv has no picture and no sound. What do I need to replace to fix the problem?

A power board will never cause a sound delay issue, if it's doing it on all channels its most likely an input issue, such as your cable box, fire stick ect

Yes, replace the tcon board, good chance it will fix it.

Start by thinking there is no problem with the tv. Look over your remote control and see if something was accidentally pushed. Check the source selections. You said you can barely see the logo. Check picture adjustment in menu. Start with the obvious before you buy.

If your Samsung TV does has sound but no picture showing up on the TVs screen you will need to reset the TV then. By unplugging your TV and wait a about 60 seconds. While the TV is unplugged press and hold the power button for about 30 seconds. After 60 seconds are plug your Samsung TV back in again after.

the voltage is ok doo you have constantly 150 v if not led blocks is bad

Here is what to check when your TV is turned on, power light is ON, but no picture is seen or sound is heard:

1 - Be sure the component you are using (Xbox, Cable, SAT, ROKU) is turned ON.
2 - Check to be sure all cable and cords are securely connected to the TV inputs and component outputs.
3 - Make sure you are on the correct input as some TV's will show a black screen if there is nothing connected to that input.
4 - Unplug the input you are trying to use from the TV (such as an HDMI Cable) and plug it back in.
5 - Check for signs of damage on all cords and cables from the TV to all components.
6 - Make sure the TV is not in ENERGY SAVE MODE, press the button on the remote control to go back to normal mode.
7 - Unplug the TV for 10 minutes to see if there was a temporary one time issue with the TV.
8 - Disconnect the TV from power for 2 minutes, then when plugging it back in PRESS AND HOLD THE POWER BUTTON ON THE TV FOR 10 to 20 SECONDS to try and force the TV to reset.
9 - If after checking all these different issues, you may have a Faulty Power Supply Board, A Bad Capacitor on the Power Supply Board, Loose Wire Harness, or Loose Ribbon Connector in the TV itself.
10 - Most likely when a TV has the power light ON but NO PICTURE and NO SOUND, it is the Power Supply Board that has failed.

BTW, here are solutions for you to play iTunes movies on Samsung smart TV

It all depends on the connections and cable.
If you are using a HDMI cable and have sound but no picture, then your TV probably needs to be fix.
if you are using a RCA cable or component cable, make sure that you have the correct TV input.
you don't specify what type of TV you have, but if I were you, I'll check the connections first.

Check the warranty, it is likely the panel will need to be replaced.

Open back an replace the video board, or converter board. Get em from Jimmys tv repair.