Panasonic Palmcorder VHSC PalmSight PV-L759 Service Manual page 89

4. A/C HEAD HORIZONTAL POSITION
ADJUSTMENT
Purpose:
To adjust the Horizontal Position of the A/C Head.
Symptom of Misadjustment:
If the Horizontal Position of the A/C Head is not properly
adjusted, maximum envelope can not be obtained at the
Neutral Position of the Tracking Control Circuit.
1. Put the unit into the service mode "I. Tracking Fix" to
defeat Auto Tracking. Refer to "Service Mode
Specification" in "Service Notes," page 1-18.
2. Connect the oscilloscope to Pin 30 (Envelope signal) on
the TP Adjustment P.C.B. Use Pin 33 (Head Switch
signal) as a trigger.
3. Play back the Alignment Tape (VFMS0004H6C).
4. Set the Screwdriver into the Hole (A) as shown.
A/C Head Unit
Screw (D)
Fig. M6-1
5. Slowly move the A/C Head Unit to the direction "A" or
"B" as shown so that the envelope is at maximum.
When move the A/C Head Unit to the direction A.
A/C Head Unit
When move the A/C Head Unit to the direction B.
A/C Head Unit
Fig. M6-2
Screwdriver
Hole (A)
Screwdriver
A
Screwdriver
B
6. To find the center of the maximum period of the
envelope, move the A/C Head Unit to confirm the limits
on either side of the maximum period.
Note:
It will be possible to confirm step 6) after performing the
following steps.
(1) Exit the "I. Tracking Fix" mode, then skip the "J. PG
Shifter" mode to enter other modes (except these 2).
Or, close the service mode.
(2) Press the Tracking Control Up Button on the
camcorder several times (count the number of times
pressed) until the maximum envelope is reduced to
1/2.
(3) Press the Tracking Control Down Button on the
camcorder several times (count the number of times
pressed) until the maximum envelope is reduced to
1/2.
(4) If the number of pressing is not the same, readjust
A/C Head horizontal position.
5. CONFIRMATION OF ENVELOPE
OUTPUT
Purpose:
To achieve a satisfactory picture and secure precise
tracking.
Symptom of Misadjustment:
If the envelope is output poorly, much noise will appear
in the picture. Then the tracking will lose precision and
the playback picture will be distorted by any slight
variation of the tracking control circuit.
1. Connect the oscilloscope to Pin 30 (Envelope signal) on
the TP Adjustment P.C.B. Use Pin 33 (Head Switch
signal) as a trigger.
2. Play back the Alignment Tape (VFMS0004H6C).
3. Confirm that the envelope waveform is as flat as
possible (V1/V(max) ≥ 0.7).
If adjustment is required, adjust S Post and/or T Post
with "–" Screwdriver. Refer to "1. Envelope Output
Adjustment."
Theoretical Waveform
V1
V1/V(max) ≥ 0.7
2-41
V V1
Fig. M7