This may be a simple fix.
Do you still have the original cable that came with it for the video OUT?
Plug this back into your playstation and TV while leaving the HDMI cable connected.
check now both HDMI channels and AV/Composite options on your source selection this should give you the display,
Now what we need to do is setup your HDMI output again.
From the menu bar,
- Go to settings
- Display Settings
- Video output settings
- choose HDMI
if you have the choice to choose OK choose it. If your screen goes blank go through your HDMI channels again and if the Playstation screen is there then select OK,
Then you can remove the composite cable again