H1 Board; H2 Board; H3 Board; K1 Board - Sony FWD-40LX1 Service Manual

3-4. H1 Board

A key input signal is sent the D3 board as a DC voltage signal. The key input signal is sent to a KEY1
signal in 0.81 V and 1.55 V when the "INPUT" and "MEMU" key are pressed. It is sent to a KEY2
signal in 0.29 V, 0.81 V, and 1.55 V when the "↓", "↑", and "OK" keys are pressed. The "POWER" key
is independently sent using a POWER_INT signal. The "POWER" key is interrupted in 0 V by a
microcomputer when it is pressed. For each signal, 3.3 V is sent when no key is pressed.

3-5. H2 Board

The H2 board mounts white LED for making logo bright. Brightness is controlled by applying 5 V to the
anode of LED and controlling the potential of a cathode.

3-6. H3 Board

The H3 board has the photosensor (IC9300) of an infrared remote controller. It sends data to the D3
board as a SIRCS signal. The H3 board also has two-color LED (D9308) that displays the status of a
unit. It controls the light emitting by applying 3.3 V to an anode and controlling a cathode.

3-7. K1 Board

Input audio signals (AU_L and AU_R) are input from the D3 board to a surround processor (IC5000)
through CN5000. In the surround processor, the volume, balance, bass, and treble are controlled and the
"hall simulation" of surrounding is processed. After that, audio L and R signals are input to class D
power amplifiers (IC5001 and IC5002) and PWM-modulated and output to a square wave of
approximately one hundred and several ten kilohertz. The square wave is integrated via a low-pass filter
(consisting of L and C) in the output stage and output through CN5001 to the SP board as an analog
waveform.

3-8. SP Board

The SP board mounts a speaker terminal (TB9500) for outputting the audio signal from the K1 board to
speakers. A filter (FL9500) is mounted between CN9500 and TB9500 to take the measures for radiation.

3-9. S Board

The S board amplifies the detection voltage from a temperature sensor (IC9400), which linearly changes
with respect to the peripheral temperature, using an operational amplifier and outputs it to the D3 board
as a DC voltage.
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FWD-40LX1