smartphone remains in black screen

[RINXD]

I have a problem with my LG-P505 its system is a cyanogenmod version 9, when the screen goes black for the sleep mode and I try to turn it on it remains black, I need help, please can someone tell me what can i do because the system seems to work good and the phone works, it had have some problems before i reinstalled its system because it was corrupted and now there is this, please help me solve this.

 

[shahbaz200]

Back screen when you lock it and screen goes off and wont turn off after minutes or restart? When this happens phone turns off almost everything to save battery (mostly in custom ROMs). Try using "SetCPU" app from play store and try increasing minumum clock rate of processor. Link to app https/play.google.com/store/apps/details?id=com.mhuang.overclocking&hl=en

Also are you using "Greenify" ? If yes see that system apps aren't selected.

If this doesn't work you can see if any other kernels are available for your device else report this isssue to Cyanogenmod developers.

 

[RINXD]

Thanks i'll try what you have told to me and i'll report the error thanks, and i wanted to tell you i haven't installed any app besides a virtual.keyboard so i don't have greenify installed.