Description Of Qd Board Circuit Operations; Rs232C Communication; Reception Of Remote Control Signals; Video Input - Sony VPL-PX20 Service Manual

3-9. Description of QD Board Circuit Operations

The functions of this board include buffer of RS232C communication, reception of remote control signals
(CIRCS signal), and video input.

3-9-1. RS232C Communication

In RS232C communication, IC1901 is used as the buffer. Signals are connected to the computer by
CN1904, and passed through IC1901, CN1903, BB board, and then the Y board for communication with
the CPU on the Y board.

3-9-2. Reception of Remote Control Signals

Signals from the remote controller connected by cable are input from I1902.
They are then inverted by Q1904, and output from Pin 5 of CN1903 to the Y board.
If not connected by remote control cable, signals received by the NF and NR boards are input from Pin 6
of CN1903, passed through J1902, and output from Pin 5 of CN1903 to the Y board again.

3-9-3. Video Input

Video signals are input from J1901, and output from CN1901 to the BA board.
The video audio signals are output from CN1902 to the QA board.

3-10. Description of K Board Circuit Operations

This board amplifies audio signals and outputs them to the main speaker.
Signals input from Pin 1 of CN2900 are amplified by IC2900 and output to the main speaker from
CN2903.
Pin 3 of CN2900 inputs mute signals. When this line is High (about 4.5V), no more signals are output to
the speaker.

3-11. Description of KS Board Circuit Operations

This board amplifies audio signals and outputs them to the sub speaker.
Signals input from Pins 3 and 5 of CN2951 are amplified in IC2950, passed through the H board from
CN2952, and output to the sub speakers.
Pin 7 of CN2951 inputs mute signals. When this line is High (about 4.5V), no more signals are output to
the speaker.
VPL-PX20/PX30
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