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Extracted text from pioneer cx 977 service manual (Ocr-read)
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C X-97 7
1. CIRCUIT DESCRIPTIONS
From divisional viewpoint, the CX-977 is roughly divided into four sections, namely, Preamplifier, Servo, Power Supply
and Loading Control.
This LSI realizes eight types of automatic adjustments (controls) through cooperative work between Preamplifier and
Servo unit.
Because the system uses the single power source (+ 5v) specification, reference voltages used in the servo system
(Preamplifier, Servo DSP and Pickup) are all Vref (2.1V).
1.1 PREAMPLIFIER (TA2153FN; IC101)
The Preamplifier processes output signals sent from the Pickup and generates signals to supply to each unit of the
next stage, that is, Servo, Demodulator or Control. It also performs power control of Pickup's laser diode. Signals from
the Pickup are I-V-converted by the Preamplifier, which is built-in in Pickup's photo detector, and then added-up by the
RF amplifier to obtain signals such as RF, FE and TE.
Reference voltage, Vref (2.1v), is output from #19 pin of the IC, and 2Vref (4.2v) is supplied to the Servo DSP as the
reference voltage to determine its D range of A/D input.
Fig. 1: TA2153FN circuit
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C X-97 7
1) Focus Error Amplifier unit
In this sub-unit, outputs from the photo detector, namely, (A+C) and (B+D), are processed in the differential amplifier
and further in the error amplifier, and then, (A+C-B-D) is output as FE signal from #16 pin of IC101 (TA2153FN).
Low frequency component of voltage FE is expressed as:
FE = (A+C-B-D) x (150k/(51k+1k)) x (60k/60k) x (120k/60k) = 5.77 times
In FE output, "S" curve of approximately 1.45 Vpp on the basis of Vref is obtained. The cutoff frequency of the
succeeding amplifier is 11.4 kHz.
2) Tracking Error Amplifier unit
In this sub-unit, outputs from the photo detector, namely, E and F, are processed in the differential amplifier and
further in the error amplifier, and then, (E-F) is output as TE signal from #14 pin of IC101 (TA2153FN).
Low frequency component of voltage TE is expressed as:
TE = (E-F) x 300k/100k x 82k/20k = 5.8 times
In TE output, "TE" waveform of approximately 1.51 Vpp on the basis of Vref is obtained. The cutoff frequency of the
succeeding amplifier is 20 kHz.
Fig. 2: FE circuit
Fig. 3: TE circuit
