Keyboard Block Diagram - Wyse WY-60 Maintenance Manual

-12 volt supply (8)--The -12V supply is derived from one of the
main transformer taps. The low voltage AC output is rectified
and filtered. The -12 volt supply is VEE for the RS-232 drivers.
+12 volt supply (9)--The +12 supply is derived from one of
the main transformer taps. The low. voltage AC output is rectified
and filtered. This supply provides filament voltage and VCC for
U26 and U27.
Flyback transformer (10)--The flyback transformer steps up the
output of the horizontal driver to provide the high voltage for
the CRT itself. In addition, the flyback transformer generates
+50 volts for the video amplifier, the +600 focus voltage, and
the brightness bias voltage (-100 VDC).
Vertical deflection circuit (11)--The vertical deflection circuit
provides the yoke with the correct vertical drive frequency to
ensure that the electron beam scans the face of the CRT at the
correct vertical repetition rate. This circuit also controls
display height and linearity.
Video amplifier (12)--The video amplifier varies the voltage on
the CRT cathode, pin 2. This modulates the beam current. Higher
beam current causes a brighter spot on the screen.
CRT
(13)--The CRT displays data by receiving a modulated electron
beam with the video signal while the beam moves across the face
of the screen. The horizontal and vertical drive signals
determine the rate of movement.
KEYBOARD
Figure 6-3 is a block diagram of the keyboard.
Figure
6-3
Keyboard Block Diagram
P1.5
- -
CMD
KEY
8051
KEYBOARD
SWITCH
DATA
CHIP
MATRIX
P1.6
,II
II
6-8