Circuit Description - Sony BVP-500 Maintenance Manual

2-3. Circuit Description

2-3. Circuit Description
Circuit description for the BVP-500/500P and CCD unit
OHB-400/500/500WS series (available separately) is
described here. The BVP-500/500P is called as BVP, and
OHB-400/500/500WS 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 CCD is mounted on the BI-91(R)/91(G) /91(B) board
respectivly. 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 source 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.
2-2
DR-302 board (OHB-400/400P 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.
DR-306 board (OHB-500/500P/500WS/500WSP)
The DR-306 is a driving board for two optical filter disks.
The main function is almost the same as the DR-302 board.
However, the DR-306 board is provided with the shortest-
turn function, which automatically selects the shortest-turn
according to a selection of optical filter using a microcom-
puter.
(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.
BVP-500
BVP-500P