Sony Mavica MVC-FD85, Руководство по обучению

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51
HI
Controller
IC404
EVR
IC902
Memory
IC406
Key
Input
Buttons
RM-95
Serial Bus
to Cam
IC501
EVR IC902 Input
Name Location Voltage
XCS Panel D/A IC902/pin 22 3.2Vp-p
HI SCK IC902/pin 19 3.4Vp-p
Time Base = 50 usec/div.
IC901 - Changes the color, contrast and brightness during the
conversion
During the video to RGB conversion within IC901, the DC levels and am-
plitudes of the signals can be altered to change the color, contrast and
brightness of the output signal. The settings for these levels are con-
trolled by DC voltages from EVR IC902.
EVR IC902 is a digital to analog converter. Serial data input instructs
IC902 to make a DC voltage that is output. Since this IC is multifunc-
tional, it produces different DC voltages to set the color, contrast and
brightness of the display. The source of the digital input data can be seen
as the EEPROM memory IC406 in this diagram:
CH1!2.00 V= PKD
CH2!2.00 V= MTB50.0us- 1.72dv ch1-
1
2
Not for
IC902
XCS
Chip
Select
SCK
clock
The data that sets the color, contrast and brightness levels are stored in
EEPROM IC406. At power On this information is accessed by HI Control-
ler IC404 and transmitted on the same common (shared) serial bus line to
IC902. A portion of the IC406 memory information is sent to EVR IC902.
From this information, IC902 makes the corresponding DC voltages for
this and other sections.
Although the information on the serial bus is present to all the ICs at the
same time, groups of information must be targeted to specific ICs on the
bus. There is a CS (chip select) line going from HI Controller IC404 to
each IC on the bus. When this CS line changes level, the information on
the bus is just for that IC.
This scope shot of the CS signal (XCS) and the serial clock (SCK) show-
ing these groups of clock/data signals is allocated to IC902, except the
very last group at bottom right. The last group has no corresponding CS
pulse into IC902, so this bus data is for another IC.
The data stored in EEPROM IC406 can be adjusted using the RM-95
Remote Commander. The service procedure for adjusting the LCD’s color,
contrast and brightness of the display is in the adjustment section of the
service manual.
IC901 - Inverts every other line of the RGB output signal
LCD Drive IC901 also inverts every other line of the RGB output signal to
keep the display operational. To understand this need, the basic LCD
operation has to be understood. As a voltage is applied to a LCD picture
element, it passes more light. The higher the voltage, the more light is
passed. Unfortunately, after a short time the LCD element no longer re-
sponds and remains dark. To keep the LCD element active, the next
voltage to the element is reversed. If the potential across the element
remains the same although the polarity has changed, the picture element
will still pass the same amount of light.
Back
Light
Picture element
+ / --
-- / +
User