S1, S2, And S3 Boards; Outline - Sony BVM-L230 Service Manual

2-4. S1, S2, and S3 Boards

2-4-1. Outline

S1, S2, and S3 boards are constituted by a measurement circuit of LED light emission amount using an
RGB color sensor (S9702) and an LED temperature measurement circuit using a digital temperature
sensor (LM75).
Figure 1 shows the location of S1, S2, and S3 boards in a BVM-L230 system. Sub addresses are assigned
to each digital temperature sensor so that they are correlated with the position information of sensors.
Therefore, backlight control does not normally operate when S1, S2, and S3 boards are not located in the
order shown in Figure 1.
S1, S2, and S3 board location (Viewed from the front panel of the unit)
Figure 2 shows the block diagram of an S1 board. S1, S2, and S3 boards only differ in a reference
2
number and the I C sub address of a digital temperature sensor. The I
ture sensor is described in 2.2 Digital temperature sensor measurement circuit.
A power supply of 5 V from the LMD2 board is used as the power of an operational amplifier
(NJU7064). A power supply of 3.3 V stepped down from 5 V using a three-terminal regulator
(R1114Q331D) is used as the power of a digital temperature sensor (LM75) and ADC (A/D converter)
(ADS7841). A SENSCNT signal is the sensor gain switching variable power output from the D/A port of
an H8 microcomputer on the LMD2 board. The SENSCNT signal is used as the reference voltage of
ADC as well as the power of an RGB color sensor. Sensor gain switching is described in 2.1.3 Sensor
gain switching. A digital temperature sensor sends LED temperature information to the H8
microcomputer on the LMD2 board through an I
sensor is output as a current. The output current is converted from a current to a voltage using an
operational amplifier in the next stage and input to the multiplexer of ADC for each RGB. ADC converts
an SENSCNT signal from analog to digital as a reference signal in the quantization precision of 12 bits.
The A/D-converted information sends the light quantity information of LED to the H8 microcomputer on
the LMD2 board through a three-wire bus.
2-12
S1 S2
RGB color sensors (Front panel of unit)
Digital temperature sensors (Rear panel of unit)
Figure 1
2 C bus. The light quantity measured using an RGB color
S3
2
C sub address of a digital tempera-
BVM-L230