Samsung un55es7150 no signal to coax. after being unplugged overnight power and hdmi. TV will power up and work fine on smart hub only .when I plug in android box to hdmi TV works for four hours appr

I will try a new main board first.

1 – Is the NO SIGNAL issue happening on just one TV?
CORRECT INPUT or SOURCE
If it is just one TV that is showing the NO SIGNAL…
-Be sure your TV is on the correct source or input as your CABLE or SAT BOX.
-Press the TV button on TV remote control to turn your TV ON.
-Press the INPUT button on your TV remote control.
-Cycle through all the inputs on your TV.
-Do this until you are on the INPUT your CABLE or SAT BOX is plugged into.
-You should then see the CABLE or SAT programming show on your TV.
HINT: Your TV will most likely list the TV INPUTS as: HDMI 1, HDMI 2, HDMI 3, VGA, Component 1, Component 2, and so on.
If you still see NO SIGNAL on your TV screen, see the next step below…

2 – If you have your TV on the correct INPUT or SOURCE and you still see NO SIGNAL…
CABLE OR SAT BOX NEEDS RESET
-Remove or unplug the power cable from the Cable TV or SAT set top box.
-Keep it unplugged for 2 to 3 minutes.
-Plug the power cable back into your Cable or SAT set top box.
-Give it some time for the Cable or SAT box to power up, get the signal, and initialize.
If you still see NO SIGNAL on your TV screen, see the next step below…

3 – If you have reset the Cable or SAT box and still have the NO SIGNAL…
UNPLUG THE CABLE GOING FROM THE TV TO YOUR CABLE OR SAT BOX
-Remove the HDMI cable or other cables from your Cable TV or SAT set top box.
-Keep the cable unplugged for 2 to 3 minutes.
-Plug the HDMI cable or other cables back in.
-Give it some time for the Cable or SAT box to get the signal and initialize.
HINT: Make sure all the cables that are connected to your Cable or SAT box and your TV are tight, undamaged, and secured.

4 – If all of your TVs are affected with the NO SIGNAL screen…
BE SURE THE COAX CABLES OR ETHERNET CABLES ARE SECURE or CABLE OR SAT IS DOWN TEMPORARILY
-Be sure to check the ones where the CABLE or SAT come into your home.
-Be sure ALL Ethernet and Coax cables are secure.
-Call your CABLE or SAT provider to see if there is an outage.
-Realign your Dish if you have SATELLITE.

You mention two separate issues, WiFi and smart hub. As you know Samsung built in manual is the worst idea ever. There is no picture of the complete rear panel connection for example.
If the smart hub is the actual WiFi antenna then if your system doesn't recognize Smart Hub then you have a bad smart hub.
to test smart hub plug something into hub ( DVD HDMI, video game) If your remote has smart hub button press and see what appears. Otherwise select source on remote see if your attached item appears. (That would indicate smart hub does talk to TV)!
Since you can access your network when hard wired your network password is stored.
Once you have verified Smart Hub is functional then work on WiFi.
i will say my Samsung is 3 ft from my router and hard wired for better streaming speed.
I use Bluetooth access to share photos from IPads.
I would leave TV hard wired.

Fault at its main digital board. Short circuited component/s at it. Contact any service technician; or the authorized service center. If you wish to get some details; check the site linked here. Surf the site with patience. Pull up older posts.
http://electronicshelponline.blogspot.com/
In most cases, the main board might have to be replaced. If so, a software [firmware] update too might be necessary.
Before going further; try a hard reset first. If it does not help you, replace the main digital board. There are two methods to reset TVs. The first is simple to do; a Hard Reset. The other is somewhat skilled; is a Factory Reset (System Reset). To make it a hard reset, just unplug the TV from AC mains wall socket, and re-plug it back after 15 minutes or so. If you do this by overnight is better. This procedure will make it a hard reset. If you want to make it a system reset [Factory Reset]; you have to enter its service mode option, and select the factory reset option. If you wish to get some details; visit the site linked here.

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What is the problem you faces with this TV? Provide more details please. If you wish to get some details, check the site linked here. Pull up older posts. Check the site in 'Mosaic' view. It will make search easy. Electro help

That HDMI connection hub port it some how got short and it dead.Tries other HDMI connections hubs.If all are like that they are all dead.All HDMI hubs ports connections are link together.If one dies usually all HDMI hubs dies together.Than ur tv Tuner signal board will not have anymore HDMI hubs functions connections at all,none of the HDMI hubs will work again ever.Have happen to mine Samung tv,so now i have to stop using HDMI hubs all together.

That HDMI connection hub might have shorted out and already dead.Tries tv unplug,replug it back in like about an hour later.For the tv to do a resetting itself back to the factory setting.Try using that HDMI connection hub again might work or not.Try other HDMI hubs for new connections for better chances for the tv to work with HDMI hubs connections again.

Tries tv and cable or satalite boxes unplug,replug it back for like about an hour later.By letting tv resetting itself back to the factory setting and those pay boxes upgrading it softwares.The tv HDMI signal for the tv incomming broadcasting signal should be back,if not, tv might have a dead HDMI cable or that the HDMI 1 hub it plug in is shorted and dead.

if u have placed your DVD next to your tv ... just maintain distance between then and check out