NEC FP1355 Service Manual

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Contents

NEC FP1355 Service Manual Manual pdf 51 page image

1 - 451.8 Deflection processor block1.8.1 OutlineThe deflection processor block mainly composed of deflection processor IC generates andcontrols a variety of the following compensation waveform that are produced by this IC.The deflection processor IC is a 64pins IC of uPD61882 of IC601.The following seven points are generated and controlled by the deflection processor IC.(Refer to the block diagram of IC601 in the figure 21.)(1)Vertical deflection waveform generating circuit(2)Horizontal deflection drive waveform generating circuit(3)Distortion compensation waveform generating circuit(4)DBF compensation waveform generating circuit(5)Convergence compensation waveform generating circuit(6)Blanking waveform generating circuit(7)Moire canceling circuitMoreover, the block is provided with a small both-face board (PWB-DEFL-SUB) of 60mm X70mm.The power of the deflection processor block is +3.3V that is converted from P-OFF+5V by theregulator of IC602, and the power and GND are divided into the digital system and analogsystem in the inner circuit of IC601 in order to prevent noise interference for the waveforms.OP amplifier of IC603 uses the power of +5V and -15V, and works as the trace filter and volt-age amplification of the amplitude of the saw-toothed waveform for vertical deflection.1.8.2 Vertical deflection waveform generating circuitThe deflection processor IC (IC601) does 10-bit DAC output of the saw-toothed wave for verti-cal deflection that is synchronized with the vertical frequency input to pin 42, from pin 1 andpin 11 at both polarities (approx. 1.2V.p-p). Moreover, the center voltage IMID (approx.1.6VDC) of the saw-toothed wave is output from pin 2.To remove the noise, the OP amplifier (pins 1, 2 and 3) of the front step of IC603 removes thedifference between the waveforms of both polarities of the saw-toothed wave for vertical de-flection, using the center voltage IMID of the saw-toothed wave as the reference. From theoutput of the amplifier, the digital gradation component of the saw-toothed wave is removedwith the low pass filter that is made of R642 and C628. Moreover, pin 62 and pin 63 of IC601are the analog switch turning ON the retrace term, prevents the waveform deformation that isproduced by the low pass filter, and prevents the degradation of the linearity and the fluctua-tion of the scanning line.Moreover, the saw-toothed wave for vertical deflection is controlled to adjust the vertical pic-ture width, vertical phase and linearity.R645, R646, R647 and R649 connected to pair GND on the filter output composed of R642 andC628 are the resistor to improve the linearity of the saw-toothed wave for input vertical deflec-tion, and switches the resistance into four steps with the transistor switch of Q603 and Q604according to the vertical frequency. (Refer to Table 12.)The saw-toothed wave for vertical deflection is output to the low output impedance with the OPamplifier (pins 5, 6 and 7) of the rear step of IC603.