Pioneer cx 3016 service manual

Page 1

21 234 1234 CX-3016 F E D CB A 1.1.1 APC circuit The light output of laser diodes (LD) has largely negative thermal characteristics. If they are driven with a constant current, the laser power level will not be constant. The APC circuit is designed to control the current so that the laser power becomes constant through the monitor diode (MD). The IC AN8703FH contains two APC circuits, one for DVDs and the other for CDs. The LD current values for DVDs can be calculated by dividing the voltage between the DVDLD1 (or CDLD1 for CDs) and 5V line by 15.6 ohms (3.9 ohms x 4): approximately 26mA and 44mA for DVDs and CDs respectively. 180mV LPC01 LPC1 AN8703FH For DVD PU UNIT 2 1++ +5V DVDLD0DVDLD1 26DV D LD+5V MD 65LD 65MD 7 3.9-„¦3.9-„¦3.9-„¦ 3.9-„¦ -“ + 170mV LPC02 LPC2 For CD 4 3+ +5V CDLD0CDLD1 24 CD LD 78LD CN1101 78MD 5 3.9-„¦3.9-„¦3.9-„¦ 3.9-„¦ -“ + 1.Circuit descriptions 1.1 Front-end processor (FEP) section (AN8703FH: IC1101) The IC1101 generates servo signals for focus and tracking operations, processes the RF signal, and controls the laser power of the pickup. For servo signal processing, the IC contains a focus operational amplifier, a focus balance adjustment circuit, a three- beam tracking operational amplifier, a phase-difference tracking detection circuit, a tracking balance adjustment circuit, and an envelope detection circuit. For the RF signal processing, the AGC and equalizer functions are contained in the IC.

Page 2

3 56 78 56 78 CX-3016 F E D CB A 1.1.2 Focus error (FE) generating circuit Focus error (FE) generating circuit The signals B1 through B4, obtained by dividing the output in the pickup, are applied to the FE generating circuit. Inside the circuit, the (B1 + B3) and (B2 + B4) signals are generated via the internal resistors, fed into the variable amplifier for the focus balance adjustment, and finally the FE signal is generated by amplifying the {(B1 + B3) -“ (B2 + B4)} signal. The pin numbers and names in the brackets are for CDs. The circuits for CDs and DVDs are identical, except for the input terminals of the signals B1 through B4. B1 CN1101 16 15 13 11 AN8702 FH 60 VIN4 (52 VIN8)57 VIN1 (49 VIN5) 58 VIN2 (50 VIN6) 59 VIN3 (51 VIN7) B2 B3 B4-“ + G4 1-“f G4 1+f + -“ VHALF 1.65V22 FEOUT 21 FEN FEY FEX FE 117 AD0 VHALF MNZS26EDCUB FBAL 7Control