Servo Circuit; Switching Point; Slow Tracking Preset; Video Circuit - JVC HR-A37U Service Manual

3.2

Servo circuit

3.2.1 Switching point

Signal (A1) • Stairstep signal
(A2) • Alignment tape (SP,stairstep,NTSC) [MHP]
Mode (B) • PB
Equipment (C) • Oscilloscope
Measuring point (D1) • VIDEO OUT terminal (75Ø terminated)
(D2) • TP106 (PB. FM)
External trigger (E) • TP111 (D.FF)/slope : –
Adjustment part (F) • Jig RCU: Code "5A"
Specified value (G) • 6.5 ± 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) Set the VCR to the Auto adjust mode by transmitting the
code (F) from the Jig RCU. When the VCR enters the
stop mode, the adjustment is completed.
(6) If the VCR enters the eject mode, repeat steps (1) to (5)
again.
(7) Play back the alignment tape (A2) again, confirm that the
switching point is the specified value (G).
Trigger point
Switching point
Fig. 3-2-1a

3.2.2 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 RCU: 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).
3-2
V.sync
V. rate
Switching point
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.
3.3

Video circuit

3.3.1 Auto picture initial setting
Signal (A1) • Ext. input
(A2) • Video: Optional
(A3) • VHS tape
• EE ¥ Auto adjust (SP/LP REC ¥ PB)
Mode (B)
Adjustment part (F) • Jig RCU : Code "58"
Specified value (G) • STOP mode
Adjustment tool (H) • Jig RCU [PTU94023B]
(1) Insert the cassette tape (A3).
(2) Set the VCR to the Auto adjust mode by transmitting the
code (F) from the Jig RCU. When the VCR enters the
stop mode, the adjustment is completed. When the VCR
enters the eject mode, repeat steps (1) to (2) again.