Television comes on and then screen goes very dark. We have been able to check the menu contrast, tint, brightness, etc, but nothing helps. What do we do now?

Most likely a defective Z-SUSTAIN board failure if the video looks somewhat correct and the tv is just dark. the Z-SUSTAIN board basically powers the plasma panel and if it fails a certain way it will cause this problem with the dark video. if you can get the tv taken apart and look for part numbers off of the board on the far right looking from that back then you may be able to find the part on the internet somewhere otherwise Contact Sanyo Manufacturing Corp 1-800-877-5032. good luck