The monitor for my Dell optiplex 745 computer shows, "no input signal" than proceeds to go to sleep a few minutes later. what can I do to correct this.

Make sure the resolution is set to the correct settings to match the TV

old post.
Fergusion Dv3?
well does the FERG run on other known working PC?
test the FERG first.
or try a known good PC monitor to the 745,
these simple tests prove what end is bad.
easy no? just do it.
"it is displaying no signal."
does those words show on the screen
or are thinking this, I see no signals.
my guess is the FERG texted to the screen live no SIGNAL
that means the PC is dead, in all cases.
(or cable bad sure)
so the post her changes to DEAD PC>
1: does the PSU fan in the PC spin? PC silent is it?
ill stop here, as that is 1 step. if i show 5 steps folks get scared.

Found these Dell™ OptiPlex™ 745 Tech Specs

https://www.dell.com/downloads/global/products/optix/en/opti_745techspecs.pdf



Dell OptiPlex 745 Desktop Product Details



Dell OptiPlex 745 Ultra Small Form Specs CNET



Dell OptiPlex 745 specs Engadget

control panel add device

go to start,then pc settings,then monitor or power options the to power and sleep and change on plug to 4 hours and on battery to 10 minutes

In regards to your issue with your monitor: For a monitor to display "no signal input" there is likely a problem with the monitor making a connection to your input source (yes I know duh). First and easiest thing to fix this is to check your cables going between your computer and monitor, if your computer and monitor start out working and then fail to communicate, there is a good chance that the cable might be coming loose just enough that the connection fails. I might suggest that if you have, as you say another computer, that you try swapping monitors to check where the problem lies.

Hope this helps some.

If you want to create a new Basic Input/Output System (BIOS) password on a Dell Optiplex 745, reset the password. Resetting the password also applies if you want to remove an existing BIOS password. BIOS passwords are used to add an additional level of security to your machine. Without the correct BIOS password, your Dell Optiplex 745 will not complete the boot process. The password can be reset whether you know your current password or not.

Turn off your Dell Optiplex 745. Start the computer. Press "F2" the moment the Dell logo appears on the screen. You will only have two to three seconds to press the key. Enter your BIOS password. Navigate to the "Exit" screen. Select the "BIOS Password" setting. Enter your BIOS password and a new password if desired. Do not enter anything in the "New Password" box if you want to remove the BIOS password completely. Press "Enter" to save your password settings. Reset Forgotten Passwords Turn off your Dell Optiplex 745 and remove the power cord from the computer. Disconnect any external hardware and cables. Slide the release latch located on the back of your Optiplex 745. Lift the cover as you slide the latch. Hold the cover firmly and pivot it back on the hinges. Remove the cover from the hinges. Find the "PSWD" jumper on the motherboard. This is a two-pin jumper and should be clearly labeled. Use a flashlight and magnifying glass if you have trouble locating it. Remove the jumper from the motherboard. Replace the cover and slide it into place until the latch snaps into place. Reconnect the power cable and restart your computer. Shut down the computer after it has completely restarted. Disconnect all cables and remove the cover again. Replace the PSWD jumper. Replace the cover. Reconnect all cables and restart your computer.
b> Clearing forgotten passwords http://phubner.eng.ua.edu/Files/Optiplex 745/advfeat.htm - wp1117484

No you need another display adapter to run dual monitors

I see that this monitor has a DVI input, in additon to the VGA input. I suggest getting a suitable cable to use the DVI input, to see if the fault replicates. If it doesn't, you have identified the problem - an issue with the analogue signal processeing circuitry in either the monitor or the computer. The monitor's auto sleep analogue circuitry, for example, may not be sensing a signal, and going to sleep. BTW, if you use a DVI-DVI cable, you avoid the video signal ever going through an analogue stage, and the image will also be purer.

Press the ON/OFF switch, and hold it in for 10 seconds -- the computer will turn itself off.