Overall Function Of Ipm-92 And Ipm-93 Boards (Infrared Ir Receiver Board); Overall Function Of De-54 Board (Fm Demodulator Board); Overall Function Of Rx-47 Board - Sony PCS-1500 Service Manual

3-2. Circuit Description of the Respective Boards

3-2-2. Overall Function of IPM-92 and IPM-93 Boards (Infrared IR Receiver Board)

The block diagram of the IPM-92, IPM-93 and DE-54 boards is shown in Fig. 3-20.
The infrared signal is converted to an electrical signal by D701 and D801 (photodiode: PP701). The
electrical signal is amplified by [PRE AMP] and sent to the DE-54 board. D701 and D801 are reverse-
biased by the ANALOG_27V (27 ± 3 V) that is generated by the DE-54 board.

3-2-3. Overall Function of DE-54 Board (FM Demodulator Board)

IC301 generates a rectangular wave of about 9 kHz to which a DC component is superimposed by D301,
D302, C304 to C306 in order to generate and apply the reverse-bias (ANALOG_27V (27 ± 3 V)) across
the photodiode on the IPM-92 and IPM-93 boards. [STEP-UP]
The electrical signal (TP401, TP421) that is converted by the IPM-92 and IPM-93 boards is separated of
its carrier bandwidth signal only [BPF], and amplified by about 10 dB [RF_AMP].
These signals (TP401, TP421) are added together. However, the waveform after the signal component
below 4.1 V is sliced and removed when the input infrared light intensity is high (TP101).
The added signal is amplified by IC101 (MC10H105MEL) and its amplitude limited [LIMITER] in order
to generate the rectangular wave of 0.8 Vp-p (TP102).
In the demodulator IC121 (MC10M107MEL), the signal whose phase is delayed by the two-stage delay
elements consisting of resistor and capacitor, and the direct signal that is input after a simple buffer are
logic-EXNORed. [DEMODULATOR]
The output signal (TP121) of the EXNOR gate is the demodulated signal that still includes the high
frequency component. Only the video signal bandwidth is separated and the video signal is obtained.
[LPF (integrator)]
Because the demodulated output signal (TP141) is emphasized by the infrared transmitter, the high
frequency component is removed at the first stage of IC141 (TK15403MTL) to restore the original video
waveform (TP142). [DE_EMPHASIS]
The restored video signal is amplified by the second and the third stage of IC141 (TK15403MTL) by
about 14 dB so that output of 1 Vp-p (TP143) is obtained across the 75 Z termination. [VIDEO AMP]
The video output signal from the first stage is amplified up to 2 Vp-p from which the simple signal
detection is performed by the circuit block that has the parts reference number of the 160 series. Detec-
tion whether video signal is present or not, is performed by this circuit. When the presence of video
signal is not detected, the signal output is muted. [MUTE CONTROL]

3-2-4. Overall Function of RX-47 Board

The SIRCS signal that is transmitted from the remote commander is converted from the infrared signal to
the electrical signal and is sent to the MA-97 board via the buffer.
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