Control Of Brightness And Contrast - Sony UP-897MD Service Manual

3-2-8. Read of Buttons
The [PRINT], [OPEN], [COPY], [FEED], and jog dial
buttons on the front panel and the button on
the rear panel are monitored. Each button (not including
jog dial buttons UP and DOWN) is shifted to operation
after the falling of a signal is detected. Jog dial buttons UP
and DOWN are shifted to operation after the rising of a
signal is detected.
IC202 Signal name Function
Pin7 KEY1 OPEN
Pin 98 KEY2 PRINT
Pin 55 KEY3 COPY
Pin133 KEY4 FEED
Pin 6 JOG3 ENTER
Pin 54 JOG_UP Rotates the jog dial upward.
Pin 97 JOG_DOWN Rotates the jog dial downward.
woat) Lt Ly Ld
yous) Ly LL
JOG_UP LL Le
JOG_DOWN
UP rotation
woot) | aa Soe a ee Fa
woes) a ee
JOG_UP
DOWN rotation
UP-897MD
3-3. Video Circuit Block
3-3-1. Outline
A composite video signal is input from the BNC connector
(VIDEO IN) to the MA-132 board. 75 Q termination is
turned on and off using a slide switch on the rear panel.
After that, a signal is input to a video circuit C501) for
sync separation, low-pass filter processing, brightness/
contrast, and AGC processing. The output signal is input
to an A/D converter. The digitized signal is read to a
system control block.
3-3-2. Control of Video Circuit Block
A chroma trap filter, low-pass filter, and AGC are turned
on and off, and NTSC/PAL and THR/EE are switched
using a general-purpose port of IC202, respectively.
1¢202 Signal name Function
Pin 29 TH/EE_OUT Switches TH/EE.
H: EE L: TH
Pin 76 NTSC/PAL_SW Switches NTSC/PAL.
H: NTSC L: PAL
Pin 31 AGC_SW Turns on and
off AGC.
H: ON L: OFF
Pin 30 LPF_SW Turns on and
off the low-pass filter.
H: ON L: OFF
Pin 115 TRAP_SW Turns on and
off the trap filter.
H: ON L: OFF
3-3-3. Control of Brightness and Contrast
Brightness and contrast are controlled by inputting the
voltage, obtained using a volume control on the front
panel, to IC501 (BRIGHT: pin 38, CONTRAST: pin 39).
The gain of an internal video amplifier then changes and
can be adjusted.
3-3