Fm Waveform Linearity; Height And Tilt Of The A/C Head - JVC HR-S5950EU Service Manual

3.2.2 FM waveform linearity

•
Signal (A1) Alignment tape(SP, stairstep, PAL) [MHPE]
•
(A2) Alignment tape(LP, stairstep, PAL) [MHPE-L]
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Mode (B) PB
•
Equipment (C) Oscilloscope
•
Measuring point (D) TP106 (PB. FM)
•
External trigger (E) TP111 (D.FF)
•
Adjustment part (F) Guide roller [Mechanism assembly]
•
Specified value (G) Flat 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) Make sure that there is no significant level drop of the V.PB
FM waveform caused by the tracking operation, with its
generally parallel and linear variation ensured. Perform the
following adjustments when required. (See Fig. 3-2-2b.)
(5) Reduce the V.PB FM waveform by the tracking opera-
tion. If a drop in level is found on the left side, turn the
guide roller of the pole base assembly (supply side) with
the roller driver to make the V.PB FM waveform linear.
If a drop in level is on the right side, likewise turn the guide
roller of the pole base assembly (take-up side) with the
roller driver to make it linear. (See Fig. 3-2-2b.)
(6) Make sure that the V.PB FM waveform varies in parallel
and linearly with the tracking operation again. When re-
quired, perform fine-adjustment of the guide roller of the
pole base assembly (supply or take-up side).
(7) Unload the cassette tape once, play back the alignment
tape (A1) again and confirm the V.PB FM waveform.
(8) After adjustment, confirm that the tape wrinkling does not
occur at the roller upper or lower limits. (See Fig. 3-2-2a.)
[Perform adjustment step (9) only for the models
equipped with SP mode and EP (or LP) mode.]
(9) Repeat steps (1) to (8) by using the alignment tape (A2).
Improper
(a) GUIDE ROLLER
(b) GUIDE POLE
Fig. 3-2-2a
• Proper waveform variation
• Improper waveform variation

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 "section 2 mechanism".)
Signal
Mode
Equipment
Measuring point
External trigger
Proper
Adjustment part
Specified value
(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
Up Down
B
A
C D
Fig. 3-2-2b
•
(A) Alignment tape(SP, stairstep, PAL) [MHPE]
•
(B) PB
•
(C) Oscilloscope
•
(D1) AUDIO OUT terminal
•
(D2) TP4001 (CTL. P)
•
(E) TP111 (D.FF)
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(F) A/C head [Mechanism assembly]
•
(G) Maximum waveform
Head base
(1)
(3)
Fig. 3-2-3a
Roller driver
Guide roller
(supply side)
AUDIO OUT
CTL. P
3-3