Pioneer cx 961 service manual
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Extracted text from pioneer cx 961 service manual (Ocr-read)
Page 1
2 C X-961 1. CIRCUIT DESCRIPTIONS This unit is roughly divided into the preamplifier stage, servo unit, power supply unit and loading control unit. This LSI (large scale integrated circuit) implements eight automatic adjustments according to the combination of the preamplifier stage and servo unit used. Besides, because this system conforms to the single power supply (+5 V) specifications, the reference voltages of servo systems (preamplifier, servo DSP and pickup) are all Vref (2. 1 V). 1.1 Preamplifier (TA2150FN; IC201) The preamplifier processes output signal from the pickup, then generates signals to the servo unit, demodulator unit and control unit at the next stage, and controls power for the pickups laser diode. The signal from the pickup is I-V converted by the preamplifier built into the pickups photodetector, then added by the RF amplifier to obtain such signals as RF, FE and TE.Reference voltage Vref (2.1 V) is output from pin 19 of this IC and 2 Vref (4.2 V) is supplied as the reference voltage which determines the D range of the servo DSP A/D input. Fig.1:TA2150FN CIRCUIT
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3 C X-961 2) Tracking error amplifier unit This tracking error amplifier unit outputs photodetector output E or F from pin 14 of IC201 (TA2150FN)via an amplifier and an error amplifier assuming (E - F) as a TE signal. The low frequency component of voltage TE is expressed as TE = (E - F) ×300 k / 100 k ×155 k / 328 k ×82 k / 20 k = 5.8 times. A TE waveform of approximately 1.51 Vpp is obtained in the TE output on the basis of Vref. The cutoff frequency is 44.5 kHz or 29.4 kHz. 1) Focus error amplifier unit This focus error amplifier outputs photodetector output (A + C) or (B + D) from pin 16 of IC201 (TA2150FN) via a differential amplifier and an error amplifier assuming (A + C - B -C) as an FE signal. The low frequency component of voltage FE is expressed as FE = (A + C - B - D) ×(150 k / 62 k) ×(60 k / 60 k) ×(12 k / 60 k) = 4.84 times. An S curve of approximately 1.45 Vpp is obtained in the FE output on the basis of Vref. The cutoff frequency is 26 kHz or 133 kHz. Fig.2:FE CIRCUIT Fig.3:TE CIRCUIT