Panasonic Palmcorder VHSC PalmSight PV-L759 Service Manual page 87

1. ENVELOPE OUTPUT ADJUSTMENT
The height of the S and T Posts replacement part is preset
at the factory.
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. 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. Confirm that the RF envelope is flat enough. If not, with
Flat Headed (–) Screwdriver, adjust S and T post height
so that the envelope waveform becomes as flat as
possible (No envelope drop). If the envelope drop
appears on the left-half of the waveform, adjust S post
height. If the envelope drop appears on the right-half of
the waveform, adjust T post height.
CAUTION: Do not apply excessive pressure onto the S
and T Posts when adjusting S and T post height.
Before Adjustment
Left-half
Adjust S Post
Oscilloscope
After Adjustment
Make flat (square) as possible.
Oscilloscope
Fig. M3-1
Right-half
Adjust T Post
S Post
Cylinder
Note:
It will be possible to confirm step 4) 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 or Down button on the
camcorder. Make sure that the envelope waveform
remains flat. If not, readjust S and/or T post heights.
5. After adjustment, confirm that the tape travels without
curing at S and T posts.
If curing is apparent, readjust the height of posts.
Curing
No Good
2-39
T Post
Tape
A/C Head
Fig. M3-2
Curing
Good
No Good
Fig. M3-3