Electrical Adjustment Instructions; Test Equipment Required; Head Switching Position Adjustment - Hitachi DV-PF2U Service Manual

ELECTRICAL ADJUSTMENT INSTRUCTIONS

General Note: "CBA" is an abbreviation for
"Circuit Board Assembly."
NOTE:
1.Electrical adjustments are required after replacing
circuit components and certain mechanical parts.
It is important to do these adjustments only after
all repairs and replacements have been com-
pleted. Also, do not attempt these adjustments
unless the proper equipment is available.
2.To perform these alignment / confirmation proce-
dures, make sure that the tracking control is set in
the center position: Press either "L5 ? ? " or "K" button
on the remote control unit first, then the "PLAY"
button (Front Panel only).

Test Equipment Required

1.Oscilloscope: Dual-trace with 10:1 probe,
V-Range: 0.001~50V/Div.,
F-Range: DC~AC-20MHz
2.Alignment Tape (MH-1)
Head Switching Position Adjust-
ment
Purpose:
To determine the Head Switching point during
playback.
Symptom of Misadjustment:
May cause Head Switching noise or vertical jitter
in the picture.
Test point
TP751(V-OUT)
TP302(RF-SW) (Switching Point)
GND (MAIN CBA)
Measurement
Tape
Equipment
MH-1 Oscilloscope
Connections of Measurement Equipment
TP751
Main CBA
GND
TP302
2-4-1
Adj.Point Mode
VR501
PLAY
(SP)
Spec.
6.5H±1H
(412.7µs±60µs)
Oscilloscope
CH1
Trig. (+)
CH1
CH2
Reference Notes:
Play back the Alignment tape and adjust VR501 so
that the V-sync front edge of the CH1 video output
waveform is at the 6.5H(412.7µs) delayed position
from the rising edge of the CH2 head switching pulse
waveform.
Input
-----
CH2
Figure 1
EXT. Syncronize Trigger Point
1.0H
6.5H
Switching Pulse
V-Sync
0.5H