RPi Easy SD Card Setup - eLinux.org

No HDMI output at all
First make sure the display is powered on and switched to the right input before booting
Pi.
If you have the Wheezy (http://www.raspberrypi.org/archives/1435) image
(recommended) then try
hdmi_safe=1
Otherwise, try adding the following line to the configuration file (similar to interference
case above)
config_hdmi_boost=4
Your monitor/cable may not be asserting the hotplug signal. You can override this with:
hdmi_force_hotplug=1
Also try (http://www.raspberrypi.org/phpBB3/viewtopic.php?f=28&t=7513) the
following video options:
hdmi_group=2
hdmi_mode=4
which resolved an issue with DVI monitor reporting "input signal out of range"
As a last resort, try deleting (rename to keep backup) config.txt from the SD card.
Also check that the RasPi +5V voltage (measured from TP1 to TP2) is in the correct
range. One user found that his DVI-D monitor blanked out when +5V was too low. See
Troubleshooting Power Problems.
Here's a rare cause: A standard HDMI cable has five individual ground wires plus a
shield. Some cheap HDMI cables do not implement the individual grounds and just have
a common foil shield that's connected to the HDMI plug shells at both ends. This works
OK in most HDMI applications since most HDMI sources (like RasPi) and most
monitors connect the shells to circuit ground. However, some HDMI or DVI monitors
may requires individual ground lines. You can tell if an HDMI cable implements the
individual grounds by checking for continuity using an Ohmmeter or multimeter. You can
find the HDMI pinout for full-size connectors at Wikipedia (http://en.wikipedia.org/wiki/
HDMI) .