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The set was working great on program material and most
test signals from the Digital Video Essentials DVD, and my own
test patterns, but not the horizontal and vertical color bars and
the red and magenta full 100% screens from the DVE DVD.
The bars showed incorrect luma for different bars and color changes
vertically across the horizontal bars.
This was traced after a VERY long session with a scope (and
the chassis in the set) looking at test points at the grids
of the first video amp, I and Q demodulators (removed from sockets),
and the three CRT grids.
The luma problem was a very slight misalignment of
the RF which I had simply not done (fixed), and the other is
(not fixed) a great sensitivity to the horizontal hold
when there is a saturated color right at the start of
a lot of horiziontal lines. Its got to be just right
so the burst sync timing is just right. This does not usually matter.
The waveform when I was aligning the burst stripper looked OK but not great.
I will have to study the circuit a lot before removing the chassis, which I will
have to do anyway to insert a UHF strip.
I was worried about signal overload, but tests show the set works
OK over a 66dB range from extreme noise and barely syncing up to
the normal power of my Blonder-Tongue modulator (which is set well below
max). At high powers one sees a few percent of nonlinearities, not
visible on pictures.
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