Hitachi C1422R Service Manual page 8

Adjustments
H. T. Setting
The HT should be adjusted using R818 to obtain correct width with normal brightness and contrast settings.
A Philips complex test pattern is ideal for the operation.
A1 Control
This should be set using the 'screen' control on T401 to achieve 140V black level at the tube base cathodes
with the brightness and contrast settings normalized. In practice the black level of the individual guns will
differ and are set by I501 to achieve equal cut-off points.
White Points
These should be adjusted via service parameters 0C, 0D and CE whilst viewing a picture with little light area
to prevent beam current limiting. The parameters should be adjusted for a black to white swing of 50V ±1V
(14"), 55V ±1V (20") or 60V ±1V (21") on each of the three cathodes with the picture normalized.
Text Contrast
White balancing of the red and blue outputs, relative to the green, should be carried out to ensure pure white
text, using RV317 (R) and RV319 (B). As the picture outputs are automatically balanced, text white may be
set using picture white as a reference once the black and white points (See adjustments section) have been
set. The text contrast itself should be adjusted such, that the Text/OSD white parts are approximately 75% of
the intensity of a test pattern peak white area: this corresponds to the 75% grey blocks in part of a 'Philips
5544' type test pattern. When the text contrast service parameter is selected the TV switches to teletext mix
mode, page 101. If no text is present P100 will still appear in the top left corner of the screen together with
some text on the bottom row of the display. There is no on-screen parameter: adjust with volume control as
normal and change parameter with programme up/down keys.
AGC
The AGC take-over point should be adjusted via service parameter 13 such, that the tuner output to the
SAW filter is 600mV pk-pk (300mV per side for symmetrical tuner output) using a test pattern with no sound
carrier.
Focus
Adjust the upper control on the rear of the flyback transformer for best focus.
Positioning
Horizontal position should be adjusted via service parameter 03 so as to centre the picture. Vertical position
should be adjusted via service parameter 0B so as to centre the picture. This may be simplified by pressing
'1' with service parameter 0B selected to activate service blanking which blanks the lower half of the picture.
The edge of the blanked area may then be aligned with the tube centre marks. Service blanking is disabled
by once again pressing the '1' key.
Linearity
Horizontal linearity is fixed; no adjustment is possible. Vertical linearity is adjusted using service parameters
08 and 0A (linearity and S-correction) whilst displaying a cross hatch pattern. Adjust the linearity for evenly
spaced intervals at the top and bottom of the picture, then adjust the S-correction to achieve equal spacing
accross the whole screen.
Vertical Protection Disable
Vertical protection is used to shut down the chassis in the event of field-scan failure. For diagnostic purposes
this can be disabled by selecting service parameter OA (S-correction) and pressing the number 2 key on the
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