Circuit Description; Power Supply; Front Panel; Back Panel - Hitachi DV-P345E Service Manual

12.

CIRCUIT DESCRIPTION

12.1 POWER SUPPLY:

• Socket PL2 is the 220VAC input.
• 2.5A fuse F1 is used to protect the device against short circuit.
• Line filters and capacitors L1, C1, L5 and L6 are used to block the parasitic
coming from the mains. They also prevent the noise, produced in the circuit,
from being injected to the line.
• Voltage is rectified by using diodes D1, D2, D3 and D4. Using capacitor C3
(470µf) a DC voltage is produced. (310- 320VDC).
•
The current in the primary side of the transformer TR1 comes to the SMPS
IC (IC1 STR-A6351). The SMPS IC has a eight-pin DIP case.
•
Voltages on the secondary side are as follows: -22V, -12V, 3.3V, 5V, 15V.
• IC3 TL431 is a constant current regulator. TL431 watches the 5 volts and
supplies the required current to IC2. There are a LED and a photo transistor
in IC2. The LED inside the IC2 transmits the value of the current from IC3 to
phototransistor. Depending on the current gain of the phototransistor IC1
keeps the voltage on the 5-volt-winding constant.
• –22 Volts is used to feed the VFD (Vacuum Fluorescent Display) driver IC on
the front panel.

12.2 FRONT PANEL:

• All the functions on the front panel are controlled by IC1 (ZR36768) on the
mainboard.
• IC1 sends the commands to IC2 PT6311 via socket PL1 (pins 3,4 and 5).
• There are 16 keys scanning function, 2 LED outputs, 1 Stand-by output and
VFD drivers on IC2.
• Pin 52 is the oscillator pin and is connected via R5 56K.
• LED D6 is red in stand-by mode and green when the device is on. When
entering stand-by mode, pin 48 goes HIGH (+5V) and controls the transistor
Q2 on the power board.
• Vacuum fluorescent display MD2 is specially designed for DVD.
• The scanned keys are transmitted via IC2 pin 5 and 6 to IC1 on the
mainboard.
• IR remote control receiver module IC3 (TSOP1836) sends the commands
from the remote control directly to U1.
• Socket PL2 carries the VFD filament voltage and –22 Volts.

12.3 BACK PANEL:

• There are 1 SCART connector (PL2), 2 pieces RCA audio jacks, for audio
output, 1 coaxial digital audio output JK1 and 1 laser digital audio output MD1
on the back panel.
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