JVC DR-MV2SEU Service Manual page 34

Good
FM envelope signal
FM envelope output signal
is adjusted at maximum.
No Good
FM envelope output signal is low.
(6) Set the Tracking Control Circuit to the preset position by
pressing "PR +" button and then the VCR " " button on
the unit.
4.4.2.3 Checking/Adjustment of Envelope Waveform
Purpose:
To achieve a satisfactory picture, adjust the Guide Rollers so
that the PB FM envelope becomes as flat as possible.
Symptom of Misalignment:
If the envelope output is poor, noise will appear in the picture.
The tracking will then lose precision and the playback picture
will be distorted by any slight variation of the Tracking Control
Circuit.
(1) Connect the oscilloscope to TP301 (C-PB) on the Main
CBA. Use TP504 (RF-SW) as a trigger.
(2) Playback the Gray Scale on the Alignment Tape(MHPE-L).
Set the Tracking Control Circuit to the preset position by
pressing "PR +" button and then VCR " " button on the
unit. Adjust the height of Guide Rollers [2] and [3](Fig. 3,
Page 1-33) watching the oscilloscope display so that the
envelope becomes as flat as possible. To do this adjust-
ment, turn the top of the Guide Roller with the Guide Roller
Adj. Screwdriver.
(3) If the envelope is as shown in Fig. 7, adjust the height of
Guide Roller [2] (Refer to Fig. 3) so that the waveform looks
like the one shown in Fig. 9.
(4) If the envelope is as shown in Fig. 8, adjust the height of
Guide Roller [3] (Refer to Fig. 3) so that the waveform looks
like the one shown in Fig. 9.
(5) When Guide Rollers [2] and [3] (Refer to Fig. 3)are aligned
properly, there is no envelope drop either at the beginning
or end of track as shown in Fig. 9.
1-34 (No.YD087)
2ms
Center Position
CTL signal
Fig.7
Dropping envelope level at the beginning of track.
Dropping envelope level at the end of track.
Envelope is adjusted properly. (No envelope drop)
Note:
Upon completion of the adjustment of Guide Rollers [2] and [3]
(Refer to Fig. 3), check the X Value by pushing the "PR +"or
"PR -" buttons on the unit alternately, to check the symmetry
of the envelope. Check the number of pushes to ensure preset
position. The number of pushes of the "PR +" button on the unit
to achieve 1/2 level of envelope should match the number of
pushes of the "PR -" button on the unit from center. If required,
redo the "X Value Alignment."
Fig.8
Fig.9
Fig.10