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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 CH UP button on the remote control unit.
and then "PLAY" button.
1-C. Checking/Adjustment of Enve-
lope Waveform
Purpose:
To achieve a satisfactory picture, adjust 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 Test Tape
(9HSFL6NS8). Set the Tracking Control Circuit to the
preset position by pressing CH UP button and then
"PLAY" button on the unit. Adjust the height of Guide
Rollers [2] and [3] (Fig. M3, Page 2-3-3) watching the
oscilloscope display so that the envelope becomes
as flat as possible. To do this adjustment, turn the top
of the Guide Roller with the Guide Roller Adj. Screw-
driver.
3. If the envelope is as shown in Fig. M7, adjust the
height of Guide Roller [2] (Refer to Fig. M3) so that the
waveform looks like the one shown in Fig. M9.
4. If the envelope is as shown in Fig. M8, adjust the
height of Guide Roller [3] (Refer to Fig. M3) so that the
waveform looks like the one shown in Fig. M9.
2ms
Center Position
CTL signal
Fig. M7
5. When Guide Rollers [2] and [3] (Refer to Fig. M3) are
aligned properly, there is no envelope drop either at
the beginning or end of track as shown in Fig. M9.
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. M3), check the X Value
by pushing the CH UP or DOWN buttons alternately, to
check the symmetry of the envelope. Check the number
of pushes to ensure preset position. The number of
pushes CH UP button to achieve 1/2 level of envelope
should match the number of pushes CH DOWN button
from center. If required, redo the "X Value Alignment."
2-3-4
Fig. M8
Fig. M9
Fig. M10
H9745MA
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