Video Block - Sony CPD-G400 Training Manual
Computer monitor
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Also See for CPD-G400:
- Specifications (2 pages) ,
- Operating instructions manual (58 pages) ,
- Service bulletin (9 pages)
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Video Block
The Video Processing Block contains several stages:
•
RGB signal processing from the computer to the CRT cathodes
•
OSD for Menu features
•
CRT Bias
RGB Signal Process
Two computers can be connected to the CPD-G400 monitor. A front
panel switch selects the input used. The switch signal is applied to IC008,
which selects the RGB signal. The input switch is also connected to IC009
to simultaneously select the sync. The selected horizontal and vertical
sync signals are used to lock the oscillator inside CPU IC001.
The RGB signal is amplified by RGB Pre-amplifier IC001 and will output
this IC unless the alternate OSD signal containing menu information is
switched in. The Input/OSD switch is controlled by IC003's Blk signal.
IC002 amplifies the input or/and OSD input to a high level to drive the
CRT cathodes.
OSD
The OSD IC003 makes the menu characters, white screen (for the Aging
Mode and the Image Restoration feature) and translates the analog cath-
ode current levels (Ik) into digital data for CPU IC1001.
IC003 needs serial data, clock and the H & V oscillator inputs to support
the RGB and Blk outputs. These two outputs are used to make a menu
display or white screen. The Ik input is used when the image restoration
feature is activated from the menu. The Ik voltages are then sent out as
data to the CPU for computation.
CRT Bias
Memory IC1005 stores the CRT bias parameters. They are loaded into
the CPU when the CPU is reset at the time the power switch is pressed.
G2 and cathode DC threshold (background/cutoff) voltage data are sent
along the IIC bus into RGB Preamp IC001. IC001 translates the data into
analog voltages to make G2 and background voltages for the CRT. Addi-
tional G2 and background driver ICs are needed to make the high volt-
37
ages necessary. Adjustments to this data are made using an external
computer using DAS software.
Troubleshooting
Dark screen - Even if RGB video is input, the monitor the signal can be
inhibited at several ICs along the path:
RGB Signal Inhibited causing a Dark Screen
Blockage Location
Reason for blockage
IC008 Input Switch
Input not selected.
IC001 RGB
CPU detects no input
Preamp
sync.
No IIC data input
IC003.
IC003 Blanking
output line held HIGH
IC002 RGB Output
+80V B+ missing.
CRT
No G2 voltage.
Cutoff voltage set too
high.
No Menu Messages
No OSD or White Screen in the Aging Mode
Location
Reason
IC003 OSD
Blk output held HIGH
No H or V input
No Data or Clock
IC1001 CPU
No H or V osc output
No Data or Clock out
Check for
Slide front panel input
switch to correct position
Blk signal from IC003.
LOW = Normal. HIGH =
OSD/blk interval.
Data/Clk from CPU to
OSD IC003.
H & V sync input CPU.
Check for +80V from LV
power supply.
G2 voltage from FBT.
IC004 in and out
voltages.
IC001 Bkg output
voltages.
Check for
OSD RGB output from IC003
when Blk is HIGH.
H & V sync, data and clock
input.
H & V oscillator, data and
clock input.
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