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3.2
Servo circuit
3.2.1 Switching point
•
Signal
(A1)
Stairstep signal
•
(A2)
Alignment tape(SP, stairstep, NTSC) [MHP]
•
Mode
(B)
PB
•
TBC: OFF
•
Equipment
(C)
Oscilloscope
•
Measuring point (D1)
VIDEO OUT terminal (75Ø terminated)
•
(D2)
TP106 (PB-FM) [Main board]
•
External trigger
(E)
TP111 (D.FF)/slope : –
•
Adjustment part
(F)
Jig RCU: Code "51" or "52"
•
Specified value
(G)
8.0 ± 0.5H
•
Adjustment tool
(H)
Jig RCU [PTU94023B]
(1) Play back the signal (A1) of the alignment tape (A2).
(2) Apply the external trigger signal to D.FF (E) to observe
the VIDEO OUT waveform and V.PB FM waveform at the
measuring points (D1) and (D2).
(3) Set the VCR to the manual tracking mode.
(4) Adjust tracking so that the V.PB FM waveform becomes
maximum.
(5) Transmit the code (F) from the Jig RCU to adjust so that
the trigger point of the VIDEO OUT waveform is changed
from the trailing edge of the V.sync signal becomes the
specified value (G).
(6) Set the VCR to the stop mode or eject mode.
Trigger point
Switching point
Fig. 3-2-1a
3.2.2 D-VHS switching point
•
Signal
(A1)
Color (colour) bar
(A2)
(STD)
(A3)
(HS)
•
Mode
(B1)
PB
•
TBC: OFF
•
(B2)
D-VHS STD
•
(B3)
D-VHS HS
•
Equipment
(C)
Oscilloscope
Measuring point (D)
(STD)
(HS)
External trigger
(E)
(STD)
(HS)
•
Adjustment part
(F)
Jig RCU: Code "51" or "52"
•
Specified value
(G)
230 ± 20µsec
•
Adjustment tool
(H)
Jig RCU [PTU94023B]
(1) Play back the signal (A1) of the alignment tape (A2).
(2) Apply the external trigger signal to D.FF (E) to observe
the D-VHS envelope waveform at the measuring point
(D).
(3) Set the VCR to the manual tracking mode.
(4) Adjust tracking so that the D-VHS envelope waveform
becomes maximum.
V.sync
V. rate
Switching point
•
Alignment tape [MD-1]
•
Alignment tape [MD-1H]
•
TP606 (PB DATA1)
•
TP616 (PB DATA2)
•
TP111 (VIDEO/STD/HS1 FF)
•
TP112 (A/HS2 FF)
(5) Transmit the code (F) from the Jig RCU to adjust so that
the duration "a" from the waveform end (Hi/Low switch-
ing point of D.FF) to the rising edge of subcode area be-
comes the specified value (G).
(6) Set the VCR to the stop mode or eject mode.
(7) Play back the signal (A1) of the alignment tape (A3).
(8) Repeat steps (2) to (6) in the mode (B3).
a
D-VHS
envelope
End of waveform (D.FF signal Hi/Low switching point)
Fig. 3-2-2a
D-VHS switching point
3.2.3 Slow tracking preset
•
Signal
(A1)
Ext. input
•
(A2)
Color (colour) bar signal [NTSC]
•
Mode
(B1)
VHS SP
•
(B2)
VHS EP
•
Measuring point (D)
TV-Monitor
•
Adjustment part
(F)
Jig code "71" or "72"
•
Specified value
(G)
Minimum noise
•
Adjustment tool
(H)
Jig RCU [PTU94023B]
(1) Record the signal (A2) in the mode (B1), and play back
the recorded signal.
(2) Set the VCR to the manual tracking mode.
(3) Set the VCR to the FWD slow (+1/6x) mode.
(4) Transmit the code (F) from the Jig RCU to adjust so that
the noise bar becomes the specified value (G) on the TV
monitor in the slow mode.
(5) Set the VCR to the Stop mode.
(6) Confirm that the noise bar is (G) on the TV monitor in
the slow mode.
(7) Repeat steps (3) to (6) in the REV slow (–1/6x) mode.
(8) Repeat steps (1) to (7) in the mode (B2).
Note:
• For FWD slow (+1/6x) playback, transmit the code "08"
from the Jig RCU to enter the slow playback mode, and
transmit the code "D0" for REV slow (–1/6x) mode.
Sub code area
3-2
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