Hitachi 61swx01w Hd-ready Projection Tv Power-on And Video-gain Problems.

Equipment: Hitachi 61SWX01W HD-Ready Projection TV receiving input from a cable company. During the last couple of months, when the TV is turned on, for about the first 10 minutes or so any non-HD channel displays a skewed screen compressed vertically, but is perfectly normal when tuned to an HD channel; regardless of the channel selected, the audio is appropriate to the channel selected.  After this startup abberation ends, all channels present normal video and audio until the TV is turned off for the night.  Then... For the last two days, the brightness of the screen has progressively darkened and guidance provided in the Operating Guide, whether manual or using the Advanced Settings Ultra AI (Artificial Intelligence) feature.  No combination of Brigntness, Contrast, Color, Tint or Color Temperature had a significant effect though increasing the Brightness to maximum showed promise initially.  It is becoming difficult to make out Menu selections as the image gets darker as I don't know any way to get a light background on the screen to provide additional contrast. I hold an Extra Class Amateur Radio license so have some experience working with HV circuitry and as an operating engineer have done electrical power switchboard circuit trouble-shooting up to and including 440V. Are there any service adjustments that would boost the gain and correct the HD vs non-HD anomaly that occurs when the TV is powered up?  NOTE: I have eliminated the HD cable box as the culprit by leaving it on overnight.