Screen blanking issue in raspberry pi solved

by default, the Raspberry Pi Desktop does not have any easy-to-use screensaver software installed, although the screensaver is enabled. Firstly, you should install the X Windows screensaver application.
Once this has been installed, you can find the screensaver application under the Preferences option on the main desktop menu. This provides many options for setting up the screensaver, or disabling it completely.

sudo apt install xscreensaver


go to preferences and select screen saver

got o mode and select disable screen saver
done now your raspberry pi screen will not go blank 

Raspberry Pi HDMI display not working, solution

1)open terminal

2) type(sudo nano /boot/config.txt)

3) find (hdmi_force_hotplug=1)uncomment the # simple before the line

4) find (config_hdmi_boost=4)uncomment the # simple before the line

5) press ctrl+o

6)press enter

7) press ctrl+x

8)press enter

9) reboot your system .it,done