Electrical Adjustment Instructions; Head Switching Position Adjustment; Test Equipment Required - Sylvania DV225SL8 Service Manual

ELECTRICAL ADJUSTMENT INSTRUCTIONS

General Note: "CBA" is 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
procedures, make sure that the tracking control is
set in the center position: Press either [TRACKING
L] or [TRACKING K] button on the front panel
first, then the [PLAY] button on the front panel.

Test Equipment Required

1. Oscilloscope: Dual-trace with 10:1 probe,
V-Range: 0.001~50 V/Div.,
F-Range: DC~AC-20 MHz
2. Alignment Tape (FL8A)
Head Switching Position
Adjustment
Purpose: To determine the Head Switching position
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
Measurement
Tape
FL8A Oscilloscope
Connections of Measurement Equipment
TP751
Main CBA GND
TP302
EXT. Syncronize Trigger Point
CH1
1.0H
6.5H±1H (412.7µs±63.5µs)
CH2
Switching Pulse
Note: TP751(V-OUT), TP302(RF-SW),
VR501(Switching Point) --- Main CBA
Reference Notes:
Playback the Alignment tape and adjust VR501 so that
the V-sync front edge of the CH1 video output
waveform is at the 6.5H ± 1H (412.7 µs ± 63.5 µs)
delayed position from the rising edge of the CH2 head
switching pulse waveform.
1-7-1
Adj. Point Mode
VR501 PLAY
(SP)
Spec.
Equipment
6.5H ± 1H
(412.7µs±63.5µs)
Oscilloscope
CH1
Trig. (+)
Figure 1
0.5H
E8E00EA
Input
-----
CH2
V-Sync