User's Manual

C. VIDEO AMPLIFIER & DDC2B
VIDEO AMPLIFIER:
The video circuit mainly consists of pre-amplifier STV9211, STV9556 post amplifier and DC coupling
application, the video DC level and gain at cathode are controlled via I2C bus & software.
The red, green and blue video signals are amplified by pre-amplifier and post-amplifier, then DC couple
to CRT cathodes , three cut-off adjustments are provided to set the video black level at cathode for all
three guns, three individual gain adjustments are also provided to adjust the white balance, both cut-off
and gain controls are digital control via micro-controller.
For the beam current limit and preventing the local doming, the beam current limit will automatically
reduce the video swing in case the maximum beam current is exceeded.
A spot-killer circuit is also added to prevent the CRT damage due to spot burn out when the set is
switched off.
DDC 2B:.
Via SDA and SCL, the data about the information of the monitor, including the serial number,
production Codes, CRT type and applicable timings are stored in the EEPROM, to avoid picture
interference, the reading and writing processes are executed via I
2
C.