Circuit Description - Sony BVP-550 Maintenance Manual

2-4. Circuit Description

Circuit description for the BVP-550 and CCD unit OHB-
450/451/550/550W series (available separately) is de-
scribed here. The BVP-550 is called as BVP, and OHB-
450/451/550/550W series is called as OHB in this section.
(1) CCD Drive System (OHB)
TG-159 board
The TG-159 outputs the pulses for driving the CCD to the
DR-271 board and outputs the pulses for sampling the
CCD output to the PA-181 board.
The driving pulses are synchronized with the HD and VD
pulses input from the BVP and are output.
Pulses are generated from the VCO clock (36 MHz) of the
board. The clocks for the digital processing circuit (36
MHz, 18 MHz)are also output to the BVP.
CCD V-sub voltage, white shading data and so on are also
stored in the EEPROM of the TG-159 board.
DR-271 board
The DR-271 board converts the pulses from the TG-159
board to directly drive the CCD. The converted pulses are
transmitted to the CCD via the BI-91(R)/91(G)/91(B)
board respectively. The board also has a circuit which
makes +29 V from +15 V for the V-sub voltage. Further-
more, the board also has an interface circuit for the optical
filter.
BI-91(R)/91(G)/91(B) boards
The CCDs are mounted on the BI-91(R)/91(G) /91(B)
boards. These boards supply the driving pulses and control
voltages to the CCD.
The signals output from the CCD are sent to the PA-181
board via the emitter follower.
PA-181 board
The PA-181 board extracts video signals from the CCD
signals output from the BI-91(R) /91(G)/91(B) boards by a
correlated double sampling circuit, and amplifies the R and
G signals by one time, and the B signal by three times. The
resultant signals are output to the VA-163 board of the
BVP.
BVP-550
DR-302 board (OHB-451/451P only)
The DR-302 is a driving board for one optical filter disk,
which motor-drives a filter selected by the RCP or MSU.
The DR-302 board consists of a motor-drive circuit, and a
servo circuit comprised of a selected filter detection and
filter position voltage generation circuits.
(2) Video Signal System
VA-163 board
The VA-163 board amplifies the video signals output from
the OHB and performs the following processings:
• Black shading correction
• Gain-up control
• Blanking cleaning
• White shading correction
• Feedback clamping
• White balancing
• Flare compensation, and
• Pre-knee
In addition, it also switches between the video signals,
TEST SAW(TEST1) signal and 3-STEP TEST(TEST2)
signal.
PR-211 board
The PR-211 board converts the analog R, G, and B video
signals into digital signals with an A/D converter having
sampling/holding functions.
It generates clocks required for the A/D conversion and the
digital processings from the clocks generated by the OHB.
In addition, the PR-211 board adds a linear matrix and
detail signals to the analog-to-digital-converted R, G and B
signals.
It performs the processings such as pedestal control,
gamma correction, knee correction and white clipping for
the signals. It also performs the followings.
• Generates an internal color-bar signal and switches
between this signal and the main line signals.
• Creates detail and aperture signals from digital R and G
signals.
• Creates a skin tone singal.
• Detects signals for an auto iris, flare compensation,
DCC, and auto white/black balancings.
• Detects black/white shadings, generates a waveform to
compensate them and outputs the wavefoem to the VA-
163 board.
• Detects black levels and outputs the feedback clamp
voltage to the VA-163 board.
• Generates TEST SAW waveforms and output them to
the VA-163 board.
2-4. Circuit Description
2-3 (E)