Height And Tilt Of The A/C Head; A/C Head Phase(X-Value) - JVC HR-J691U Service Manual

3.2.3 Height and tilt of the A/C head

Note:
• Set a temporary level of the height of the A/C head in
advance to make the adjustment easier after the A/C
head has been replaced. (See "Mechanism Assembly
and Disassembly".)
•
Signal (A) Alignment tape(SP, stairstep, NTSC) [MHP]
•
Mode (B) PB
•
Equipment (C) Oscilloscope
•
Measuring point (D1) AUDIO OUT terminal
•
(D2) TP4001 (CTL. P)
•
External trigger (E) TP111 (D.FF)
•
Adjustment part (F) A/C head [Mechanism assembly]
•
Specified value (G) Maximum waveform
(1) Play back the alignment tape (A).
(2) Apply the external trigger signal to D.FF (E), to observe
the AUDIO OUT waveform and Control pulse waveform
at the measuring points (D1) and (D2) in the ALT mode.
(3) Set the VCR to the manual tracking mode.
(4) Adjust the AUDIO OUT waveform and Control pulse
waveform by turning the screws (1), (2) and (3) little by
little until both waveforms reach maximum. The screw (1)
and (3) are for adjustment of tilt and the screw (2) for azi-
muth.
(2)
A/C head
(3)
Fig. 3-2-3a
Head base
(1)
AUDIO OUT
CTL. P
3.2.4 A/C head phase (X-value)
•
Signal (A1) Alignment tape(SP, stairstep, NTSC) [MHP]
•
(A2) Alignment tape(EP, stairstep, NTSC) [MHP-L]
•
Mode (B) PB
•
Equipment (C) Oscilloscope
•
Measuring point (D) TP106 (PB. FM)
•
External trigger (E) TP111 (D.FF)
•
Adjustment part (F) A/C head base [Mechanism assembly]
•
Specified value (G) Maximum V.PB FM waveform
•
Adjustment tool (H) Roller driver [PTU94002]
(1) Play back the alignment tape (A1).
(2) Apply the external trigger signal to D.FF (E), to observe
the V.PB FM waveform at the measuring point (D).
(3) Set the VCR to the manual tracking mode.
(4) Loosen the screws (4) and (5), then set the Roller driver
to the innermost projected part of the A/C head. (See Fig.
3-2-4a.)
(5) Rotate the roller driver so that the A/C head comes clos-
est to the capstan. From there, move the A/C head back
gradually toward the drum until the point where the FM
waveform is maximized for the second time, and then
tighten the screws (4) and (5) temporarily.
(6) Play an alignment tape (A2) and set to the manual-track-
ing mode.
(7) Fine-adjust A/C head base position to maximize the FM
waveform, and then tighten the screws (4) and (5) firmly.
(8) Play alignment tapes (A1) and (A2) and confirm that the
FM waveforms are maximized when the tracking is at the
center position.
Roller driver
To the drum
Toward the capstan
Screw (4)
Head base
Toward the drum
A/C head
Screw (5)
To the capstan
Fig. 3-2-4a
Alignment tape
[SP, stairstep]
played with the
SP head
Drum side Control head position
Fig. 3-2-4b
Alignment tape
[EP(LP), stairstep]
played with the
EP(LP) head
X-value adjustment point
Capstan side
Maximum
3-3