Video System Checks And Adjustment; X'tal Osc Check (Ma-317 Board); Sync Agc Check (Ma-317 Board); White Clip/Dark Clip Check (Ma-317 Board) - Sony SLV-478 Service Manual

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2-4.

VIDEO SYSTEM CHECKS AND ADJUSTMENT

For the video system checks, follow the checking procedures given
below as a rule. The color bar video signal supplied from the pattern
generator is used as the video input signal for the video system
adjustment of the recording mode. Check that the signal satisfies
the specified value designated in the "Check of input signal" (Fig.
6-2-2)
Unless otherwise specified, set the switches to the following
positions.
• INPUT SELECT switch ............................. LINE or LINE 1
• TAPE SPEED switch ...................... SP (Remote commander)
[Checking Sequence]
1) X'tal OSC Check
2) SYNC AGC Check
3) White clip/Dark clip Check
4) Recording Y Level Check
5) Recording Chroma Level Check
6) Playback Level Check
7) VCO frequency adjustment

2-4-1. X'tal OSC Check (MA-317 Board)

Mode Playback
Signal Alignment tape: SP Color bar portion
IC201 pin %§
Measurement point
Measuring instrument Oscilloscope and Frequency counter
Specified value 3,579,545 ± 70Hz
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L 13942296513
Note: A frequency counter should be connected through a buffer
amplifier (oscilloscope, etc.) having a high impedance and
a low capacitance.
[Check Method]
1) Check that the oscillation frequency satisfies the specified value
and that the oscillation voltage is 500 ± 200mVp-p.
3,579,545 ± 70Hz
Fig. 6-2-5.
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(Remote commander)
500 ± 200mVp-p
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2-4-2. SYNC AGC Check (MA-317 Board)

Mode
Signal
Measurement point
Measuring instrument
Specified value
[Check Method]
1) Check that the Video signal level (A) satisfies the specified
value.

2-4-3. White Clip/Dark Clip Check (MA-317 Board)

Mode
Signal
Measurement point
Q Q
Measuring instrument
3 6 7 1 3 1 5
Specified value
Connect a resistor of 3.3kΩ between IC201 pin $™ and GND.
[Check Method]
1) Check that the white clip level is 190 ± 15% to the white (100%)
level.
2) Check that the dark chip level is 50 ± 10% to the white (100%)
level.
White (100%)
100%
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6-4
9 4 2 8
E-E
Color bar
IC201 pin #•
Oscilloscope
A=2.10 ± 0.14Vp-p
White (100%)
A
H
Fig. 6-2-6.
E-E
Color bar
IC201 pin #¶
Oscilloscope
0 5 8 2 9 9 4
White clip : 190 ± 10%
Dark clip : 58.5 ± 5%
A
B
Fig. 6-2-7.
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