Sony DXC-S500, Service Manual

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6-2
DXC-S500 (E)
Protection function
Timer latch-type short-circuit protection circuit
An SCP comparator detects each comparator output voltage level for output short-circuit detection.
When at least one output voltage exceeds 2.1 V, a timer circuit operates and the capacitor externally
installed at pin 23 (SCP pin) of IC201 starts charging. A latch circuit operates when an output voltage
does not return to the normal voltage until this voltage increases to a Vbe voltage. At that time, an output
transistor is turned off to stop the function. The power can be turned on again for recovery when this
protection circuit operates.
Malfunction prevention circuit at the time of low input voltage
The transition state during the power-on sequence or the instantaneous decrease in a supply voltage
induces the malfunction of a control circuit and causes the damage or deterioration of a system. At the
time of a low input voltage, the malfunction prevention function turns off an output transistor to prevent
malfunction by detecting the level of a supply voltage and resetting a latch circuit.
In circuit configuration, T201 on the PS-613 board outputs
_
7.5 V and 15 V of a camera at the winding
ratio of a transformer.
Q202 through Q204 control each power supply and contain that exceeding the output current of each
power supply.
The voltage generated on the PS-613 board is fed from each pin of CN201 to the CA-46 and PA-267
boards .
CN202 is a cooling device connector. Power supply is fed from each pin of CN202. A voltage is not
fixed because the control voltage corresponding to the CCD temperature is input from pin 10 of CN201.
6-2. IF-874 Board
The IF-874 board is a connector interface board into which a PC card is inserted.
A card power of 5 V and a circuit power that are used in a PC card are supplied from CN301. A control
line that turns on and off the power to the card is input when the insertion of a card is detected. The
control line consists of a RD/WR signal and reset signal in the power I/O mode. ARMCPU card bus
address signals FA1 to FA10, data bus lines FD0 to FD15, and card control lines are input from CN302.
CN303 is a 68-pin PC card connector into which a PC card is inserted.
IC301 to IC307 are used to make the internal interface between the PC card and ARMCPU. IC301 to
IC307 convert a power signal of 3 V to 5 V and open the bus according to the card insertion and
extraction.
6-3. PD-106 Board
The PD-106 board is a 3.5-inch LCD monitor display drive board that has internal CCU.
The PD-106 board mainly consists of a lighting circuit in the back light block adjacent to the rear of 3.5-
inch LCD, a circuit that converts a video (Y/C input) signal into a Y signal (luminance) and color-
difference signal (constituted by an R-Y signal and B-Y signal), and a circuit that converts a color-
difference signal into an LCD RGB signal and generates an LCD panel driving signal. The PD-106 board
also mounts a D/A converter for an electronic variable resistor (EVR) to perform each control operation.
This board stores the adjustment data on the PD-106 board by mounting EEPROM.