Wrong Screen resolution - lost use of monitor even on rebooting

[newtusmaximus]

Switched monitor off - and unplugged for half an hour.
Rebooted - using nomodeset grub edit , F10 and promptly switched off monitor
and let it finish boot.
Had other things to do so left pc booted and running but not logged on , monitor off.
Came back and log on screen was at higher resolution - icons smaller size.
Went into menu/settings/display = default  BUT set as 1024x768 @ 61Hz - Could not change either Hz or rsesolution.

tty1
HP-Compaq-dc7700p-Ultra-slim-Desktop:~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 1024 x 768, maximum 1024 x 768
default connected 1024x768+0+0 0mm x 0mm
  1024x768      61.00*
  800x600      61.00 
  640x480      60.00 

Restart via menu  ( not  via off)
reboots - logon  flash screen  bigger fonts, login  and x/y oscillations again.

tty1 login, poweroff
Reboot, escape key, nomodeset grub alteration, F10, large fonts/icons  back to 640x480.  again can't alter via menu/settings/display.

HP-Compaq-dc7700p-Ultra-slim-Desktop:~$ xrandr
xrandr: Failed to get size of gamma for output default
Screen 0: minimum 640 x 480, current 640 x 480, maximum 640 x 480
default connected 640x480+0+0 0mm x 0mm
  640x480      73.00*

Round and round we go again