Sony HDCAM HDW-F900R Maintenance Manual page 87

. Protection circuit when output circuit is shorted
A diode or transistor is connected to the respective output
circuits. They are reverse-biased during normal operation
of the unit so that they are turned off.
However, if any single output circuit is shorted, or if the
output power is not supplied due to any abnormality, the
above diode or transistor and Q132 on the RE-187B board
are turned on so that Q133 outputs the H SHUT DOWN
signal.
The H SHUT DOWN signal stops sending the clock signal
to the respective ICs and all of the power outputs are
stopped.
The H SHUT DOWN signal is also sent to the FET
CONTROLLER (IC109) on the CNB-23 board where
supply source of the UNREG +12 V power is stopped.
. Voltage control circuit
The power supply circuits of +1.5 V, +1.8 V, +2.5 V,
+3.3 V, +5 V and +9.3 V are step-down type chopper
circuits.
The power supply circuits of _5 V and _8.5 V are inverted
type chopper circuits. The power supply circuit of +46 V
is a step-up type chopper circuit.
The power supply circuits of +15.5 V and +28 V are
described as follows.
The primary winding of the transformer T101 of the RE-
187B board not only functions as the coil (L) of the _8.5 V
inverted type chopper, but is also used to step up its
driving current by transformer coupling, and the stepped-
up voltage is half-wave rectified to generate the above
power voltage.
The output voltage is again DC-biased by +9.3 V to
generate the powers of +15.5 V and +28 V.
The output power voltages of the above-described two
power supply systems are not controlled by the controller
IC, so the output voltages are stabilized by a series regula-
tor consisting of Q128, Q129 and IC106.
HDW-F900R/V1 (E)
1-26-9. Option Board (DC-110A Board, DC-
139 Board, MY-99 Board, PM-23
Board)
Down converter board
(DC-110A board : HKDW-702)
The down converter board DC-110A performs the follow-
ing signal processing.
The 1125 HD signal (10-bit parallel component Y/C
signal) that is input from the DCP-43 board is converted to
the D1 parallel signal (component Y/C digital parallel SD
signal) by IC23 so that the SD VBS, the SDI is output.
The parallel HD signal is down-converted to the D1
parallel signal (4 : 2 : 2) and so that the composite signal is
output via the encoder (IC202).
At the same time, the signal is multiplexed with the digital
audio signal by IC403 and the multiplexed signal is output
as the SDI signal.
The composite signal is not only output to the TEST OUT
connector via the character mix circuit on the DCP-43
board, but also output to the VIDEO OUT connector via
the 75 Z driver on the DC-110A board.
The VIDEO OUT connector can also output the SDI
signal. Selection of whether the composite signal or the
SDI signal will be output is determined by using the menu.
(OPERATION menu, OUTPUT SEL display : SD REAR
BNC OUT)
(For more details, refer to "4-4. Operation Menu".)
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