Sony HDW-750 Maintenance Manual page 87

The combination of audio volume controls of the VCA block are specified using the menu (excluding
AGC).
The control voltages for VCA that are supplied from the FRONT VR control, the SIDE VR control or the
AGC-VR control are selected by the analog switch (IC101 and IC201) on the FP-121 board. The selected
control voltage for VCA is supplied from IC11 to VCA (IC12 : THAT2181B) or from IC15 to VCA
(IC13). The variable control range of the audio gain is from 0 dB to _∞ dB.
(1) FRONT VR control only
(When FRONT is selected by the maintenance menu
07 : VTR MODE-2 REAR 1 (or 2) WRR VR SEL)
_4.3 VDC
UNITY
+5 VDC
FRONT
-VR
X
_30 dBU
MIC/LINE
CH1
Y
(3) FRONT VR control + SIDE VR control
(When F+S1 (or 2) is selected by the maintenance menu
07 : VTR MODE-2 REAR 1 (or 2) WRR VR SEL)
+5 VDC
_4.3 VDC
UNITY
FRONT
-VR
SIDE
-VR
X
_30 dBU
MIC/LINE
CH1
Y
The playback signal passes through the DVP-18 board, MB-898 board and IC101 and the audio control IC
(IC103 : CNF1) of the APR-59 board, and is output from the audio control IC (IC103 : DA1) as the 16-bit
serial signal for D/A.
The 16-bit serial signal for D/A is sent to the monitor channel selector switch (S106) on the FP-121 board
that drives the digital switch (IC105) in order to select either one of CH1 and CH2 or CH3 and CH4 or
CA3 and CA4. The selected monitor signal is sent to the 16-bit D/A CONVERTER (IC521) on the FP-
121 board.
The selected monitor signal passes through the differential amplifier (IC504 and IC505 : balanced-to-
unbalanced conversion), T-type twin filter block (Q503 to Q506), amplifier (IC506), analog switch
(IC507 : EE sound or playback sound selector), OUT-Limiter and amplifier block (IC512 and IC513),
balanced-to-unbalanced conversion amplifier (IC514), MB-898 board, CNB-15 board and final stage
amplifier (IC101) of the AL-43 board. It is finally output from the 5-pin XLR connector on the AXM-24
board.
HDW-750/750CE V1
IC11
IC12
VCA
THAT
2181B
Already
adjusted
IC11
during SIDE
IC12
VCA
THAT
2181B
Fig.3 Block diagram, combinations of VR controls
(2) SIDE VR control only
(When S1 (or S2) is selected by the maintenance menu
07 : VTR MODE-2 REAR 1 (or 2) WRR VR SEL)
+4.7 VDC
_4.3 VDC
UNITY
R11
(SIDE-VR
voltage)
SIDE
-VR
X
_30 dBU
MIC/LINE
CH1
Y
(4) AUTO
(When AUTO is selected by the maintenance menu
07 : VTR MODE-2 AU SG (1 kHz))
+4.7 VDC
_4.3 VDC
R11
UNITY
(SIDE-VR
voltage)
RV12
X
_30 dBU
MIC/LINE
CH1
Y
1-26. Circuit Description
1-26-4. Audio System
IC11
IC12
VCA
THAT
2181B
IC11
IC12
_42 dBU
VCA
THAT
2181B
1-71