HD700 Grayscale Tracking
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Tip from Louis Carliner: "I
have not been satisfied with the best attainable grayscale tracking of the Dwin HD700
despite best effort. However, I believe that I have found what I was doing wrong and what
Basically, the solution is simply to "Hold your nose and defocus the blue".
In the case of the Dwin, the blue electrical focus is correct for the amount of defocus
required and should not be disturbed. On my third HD700 I was tasked to do recently, I
started immediately to rough-in the grayscale. The results ranged from some 5700 degrees K
at 20 IRE with good dX/dY-dE values to 6800 at the mid-range and dropping to some 6200 at
the top end and with a respectable looking grayscale on the vertical pluge pattern of
Video Essentials. However, when I performed my usual stuff and tightened up all of the
tube focus, including the blue tube, the grayscale appearance went south. It ranged from a
slightly greenish tinge below 20-IRE peaking at some 8900 at the low mid region to some
5700 at the top end. I immediately proceeded to restore the blue defocus, taking advantage
of the fact that centering shifts at the focus point (I had not yet recentered convergence
after focusing, fortunately) with the result that the original readings were restored, as
well as that realistic look that was not fully present in the sharp blue focus version.
Normally, with most displays (the Panasonic r/p's being an exception and may also need
the blue defocus) the linear blue circuitry focus so well that the loss of definition
becomes more noticeable than the loss of depth and realism. The best grayscale tracking I
have yet seen (after adjustment, of course!) has been with the Mitsubishi ...7 models and
without any defocusing! The most that blue defocus will gain is some 400 to 600 degrees
flattening of the grayscale. Values not enough to influence differences in the depth and
realism portion of the picture improvement versus definition.
What is happening is by defocusing the blue gun, more of the tube phosphor surface is
being used. In the case of the Dwin a blue outlining of the letters can be observed.
Limits on scan rates is imposed by blue defocus to the extent that lines cannot be allowed
to gun together, including the blue! If it happens, blurriness big time happens and the
effects of line doubler artifacts become more annoying."