I have an S3U in my home. WHEN I turn it on I get a message no input signal. How do I fix this?

No. The T-Con board controls the picture. The main board has partially failed. You can get parts from here:

check cables first...and then go to menu to assess if the unit itself is responsible for.

The "PROTECT" and "PUSH POWER" messages will flash alternately when the protective device of the amplifier has been activated because a strong signal was input, or if there is a short-circuit detected. Press the POWER button on the unit to turn off the system, and check the following items after "STANDBY" disappears.

1) Are the + and - speaker cords short-circuited?
2) Are you using only the specified speakers?.
3) Is anything blocking the ventilation holes of the system?

You may also refer to the following link for additional troubleshooting steps.
PROTECT and PUSH POWER flash alternately on the amplifier screen

Go into HP screen menu and turn off the display notification

Turned on computer (Pavilion a1657c), HD light operates, Monitor has little window saying:
HDMI Input: No Input Signal
VGA Input: No Input Signal
Recommended Settings: 1920x1080 - 60hz
Changed from the monitor that came with it (HP f2105 digital ouyput) to my Samsung analog and same message comes on dark screen.

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Be sure you have your input corrected to the feed you are accepting. You may need input 1, per say, you may be on input 2. If you select to use antenna, be sure you are on the correct channel advised by your Direct TV Servicer. The only other possibility would be, you are not getting a signal into the TV box. Follow the lead that comes into the box and see if it does connect to the outdoor antenna. As you suggest, one or both boxes work on the other TV. Thanks for asking and show all hands of support!

The message input signal means no signal is being feed to the monitor.
Check the cable use to connect the monitor to the video card.. fix and secure the connection.
If the computer is reading and you know its working, check the video card.
Turn off the CPU disconnect the video card from the motherboard and reconnect.
Try to open your CPU and see if it reacts with your monitor. If nothing happens replace your video card

first thing I would do is to make sure your cable box is turned on. if not fixed, make sure you have the correct input. this can be done by viewing all the inputs that the tv has by pressing the input button on your remote until you find a picture. if it is still not working, make sure you have you cable run right. there should be one cable running to the cable box and into the port labeled antenna or input, then anouther labed cable running from the output port to the tv. there might also be a vcr or dvd play inbetween. if that is the case, the cabel running from the cable box should go to the input of the vcr or dvd play and the output line should go to the tv. any equipment inbetween the cable box and tv should be turned on when viewing you cabel tv. you will also have to make sure that any equipment inbetween is running off the cabel input.

well overall the tv isn't too reliable but perhaps you have the input on comp(vga) if you do that it says no signal and shuts off, try changing the channel by click either the channel up or down button, or just press the input button.
that would be the easy fix, or your tv is just broken like so many others, myself included