The 7.2–inch monochrome LCD is provided with a contrast adjustment
potentiometer and video signal adjustment switches.
The contrast is adjusted when the printed–circuit board for LCD or panel
is replaced. Otherwise, it should not be necessary to use the adjustment
7.2–inch monochrome LCD (rear view)
This adjustment is made to compensate for variations between,
printed–circuit board for LCD and LCD panel. When a printed–circuit
board for LCD or panel is replaced, the following adjustment must be
made. If the entire LCD unit is replaced, however, no adjustment is
(a) First, adjust potentiometer VRP1 until the displayed characters (all
black areas) appear white.
(b)Rotate the potentiometer in the opposite direction until the
characters appear clear and black.
This potentiometer is factory–set and normally need not be adjusted
by the user. If the setting is changed by mistake, re–adjust it according
to the following procedure. Note that some versions of this
printed–circuit board do not have this potentiometer; adjustment is
(a) Using the check pins, observe HS and CLK on an oscilloscope.
(b)Over part of the range of potentiometer VR1, the positive–going
edge of HS will be almost in phase with the positive–going edge
of the CLK. Rotating the potentiometer a little does not change the
phase difference. Set the potentiometer to the midpoint of this
(c) After completing the adjustment, confirm that the display does not