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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 completed.
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 channel "
▼
" or "
▲
"
button first, then the "PLAY" button (VCR’s 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 play-
back.
Symptom of Misadjustment:
May cause Head Switching noise or vertical jitter in
the picture.
Test Point
Adj. Point
Mode
Input
TP751(V-OUT)
TP302(RF-SW)
TP511(GND)
VR501
(Switching Point)
(MAIN CBA)
PLAY
(SP)
----
Tape
Measurement
Equipment
Spec.
MH-1
Oscilloscope
6.5H
±
1H
(412.7
µ
s
±
60
µ
s)
Connections of Measurement Equipment
Figure 1
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(412.7
µ
s) delayed position from the rising
edge of the CH2 head switching pulse waveform.
Oscilloscope
Main CBA
TP751
CH1 CH2
Trig. (+)
TP511
TP302
EXT. Syncronize Trigger Point
1.0H
CH1
CH2
Switching Pulse
6.5H
V-Sync
0.5H
1-7-1
Summary of Contents for VT-FX685A
Page 23: ...1 9 3 1 9 4 1 9 5 Main 1 4 Schematic Diagram PWR VCR PM REC ...
Page 24: ...1 9 6 1 9 7 1 9 8 Main 2 4 Schematic Diagram ...
Page 26: ...1 9 11 1 9 12 Main 4 4 Schematic Diagram ...
Page 27: ...1 9 13 1 9 14 Function Schematic Diagram ...
Page 28: ...Function CBA Top View Function CBA Bottom View 1 9 15 1 9 16 ...
Page 54: ... 48 49 S 17 Slide Holder S Slide Holder T S 18 50 L 3 Fig DM17 52 51 Slide P 9 Fig DM18 2 4 8 ...