Electrical Adjustment - JVC HR-P201ER Service Manual

3.3 Electrical adjustment

Note:
The following adjustment procedures are not only necessary
after replacement of consumable mechanical parts or board
assemblies, but are also provided as references to be referred
to when servicing the electrical circuitry.
In case of trouble with the electrical circuitry, always begin a
service by identifying the defective points by using the measur-
ing instruments as described in the following electrical adjust-
ment procedures. After this, proceed to the repair,
replacement and/or adjustment. If the required measuring in-
struments are not available in the field, do not change the ad-
justment parts (variable resistor, etc.) carelessly.
3.3.1 Servo circuit
3.3.1.1 Switching point
Signal (A1) • Stairstep signal
(A2) • Alignment tape(SP,stairstep,PAL) [MHPE]
(A3) • Alignment tape(LP,stairstep,PAL) [MHPE-L]
Mode (B) • PB
Equipment (C) • Oscilloscope
Measuring point (D) • VIDEO OUT terminal (75 ohm terminated)
• TP106 (PB. FM)
External trigger (E) • TP111 (D.FF)
Adjustment part (F) • Jig RCU: Code "5A"
Specified value (G) • 6.5 ± 0.5H
Adjustment tool (H) • Jig RCU [PTU94023B]
<2 Head Model>
(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).
<4 Head Model>
(1) Play back the signal (A1) of the alignment tape (A3).
(2) Perform the above steps (2) to (6).
Trigger point
Switching point
Fig.3-3-1a Switching point
1-18 (No.82992)
3.3.1.2
Signal
Mode (Notes)
Measuring point (D)
Adjustment part (F)
Specified value (G)
Adjustment tool (H)
(1) Record the signal (A2) in the mode (B), 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 mon-
itor 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) Record the signal (A3) in the mode (B), and play back the
recorded signal.
(8) Repeat steps (2) to (6).
(9) Repeat steps (2) to (8) in the REV slow (-1/6x) mode.
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.
• For 2 Head models, adjustments should generally be
performed in SP recording mode. However, for 2 Head
models equipped with LP (or EP) mode, adjustments
should be performed in LP (or EP) recording mode only.
3.3.2 Syscon circuit
Notes:
• When perform this adjustment, remove the Mechanism
assembly.
3.3.2.1
Signal
Mode
Equipment
Measuring point (D1)
V.sync
Adjustment part (F)
Specified value (G1) • 1024.008 ± 0.001 Hz
(1) Connect the frequency counter to the measuring point
(D1).
V. rate
(2) Connect the short wire between the short point (D2) and
(D3) to GND.
(3) Short the point (D4) and GND in order to reset the micro-
processor of the Syscon.
(4) Disconnect the short wire between the short point (D3) and
GND.
(5) Adjust the Adjustment part (F) so that the output frequency
becomes the specified value (G).
Slow tracking preset
(A1) • Ext. input
(A2) • Color (colour) bar signal [PAL]
(A3) • Color (colour) bar signal [NTSC]
(B) 2 Head Model
• VHS LP (EP)
4 Head Model
• VHS SP/LP (EP)
• TV-Monitor
• Jig RCU: Code "71"or "72"
• Minimum noise
• Jig RCU [PTU94023B]
Timer clock
(A1) • No signal
(B) • EE
(C) • Frequency counter
• IC3001 pin 29
(D2) • IC3001 pin 31
(D3) • IC3001 pin 32
(D4) • IC3001 pin 25
• C3042 (TIMER CLOCK)
(976.554 ± 0.001 µsec)