Symptoms:

• You can take exposures, but they show little or no sensitivity to light.
• Each exposure looks like a bias frame. The pixel values change from exposure to exposure, but no spectrum or image is formed.
• The bias (overscan) regions show abnormally low values, like ~40 or 50 DN, instead of the nominal value of ~700 DN.

Problem:

• Analog power to the CCD is not enabled, possibly due to a problem during rebooting of the CCD crate.

Solution:

• Reboot the CCD crate from a TIP session as described here. Good output should resemble this. An example of bad output is here.
• If, after several reboots, the problem still exists, try cycling power on the CCD controller