Pioneer cx 3098 service manual
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Extracted text from pioneer cx 3098 service manual (Ocr-read)
Page 1
21 234 1234 F E D CB A CX-3098 1. CIRCUIT DESCRIPTIONS Recently, most CD LSI's have included DAC, RF amplifier and other peripheral circuits, as well as the core circuit DSP. This series of mechanisms employ a multi-task LSI UPD63761GJ, which has CD-ROM decoder and MP3/WMA decoder in addition to the CD block as shown in the Fig.1.0.1. This enables to reproduce a CD-ROM where MP3/WMA data is recorded. Fig.1.0.1 Block diagram of CD LSI UPD63761GJ A-F UPD63761GJ Audio outputDigital servoRF amplifierCD-ROM decoder EFM Signal processor MicrocomputerSRAM(1Mbit) Buffer memory controller(BMC) DAC MP3/WMA decoder
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3 56 78 F E D CB A 56 78 CX-3098 1.1 PREAMPLIFIER BLOCK (UPD63761GJ: IC201) In the preamplifier block, the pickup output signals are processed to generate signals that are used for the next-stage blocks: the servo block, demodulator, and control. After I/V-converted by the preamplifier with built-in photo detectors (inside the pickup), the signals are applied to the preamplifier block in the CD LSI UPD63761GJ (IC201). After added by the RF amplifier in this block, these signals are used to produce necessary signals such as RF, FE, TE, and TE zero-cross signals. The CD LSI employs a single power supply system of + 3.3V. Therefore, the REFO (1.65V) is used as the reference volt- age both for this CD LSI and the pickup. The LSI produces the REFO signal by using the REFOUT via the buffer amplifi- er and outputs from the pin 133. All the measurements should be made based on this REFO. Caution: Be careful not to short the REFO and GRD when measuring. 1.1.1 APC (Automatic Power Control) A laser diode has extremely negative temperature characteristics in optical output at constant-current drive. To keep the output constant, the LD current is controlled by monitor diodes. This is called the APC circuit. The LD current is calculated at about 30mA, which is the voltage between LD1 and V3R3D divided by 7.5 (ohms). Fig. 1.1.1 APC PICKUP UNIT CD CORE UNIT MD VR LD- LD+5 7 15 145 7 15 14 100P R1 R1100/162SB1132 1SS355 1R5 x 5 ++ - + - + - PD VREF REG 1.25V APN LDS UPD63761GJLD 143 142 6R5K 1K 6R5K 1K 110K100K 100K 3P