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8. Electrical alignments
8.1
Measuring instruments
The following instruments are required to carry out the
electrical setting work:
1. Dual trace oscilloscope
Voltage range
Frequency range
Probe
2. Digital Multimeter
3. Frequency meter
4. Sine-wave generator
5. Test pattern generator
6. Plastic adjustment tool
7. Isolating transformer (regulating transformer)
8. VHS test cassette 4822 397 30103
SPC test cassette 4822 397 30268
VHS test cassette
Counter Reading Start
0
0040 ±8
Video
Blank B&W Pattern
Audio
Blank 6kHz (mono)
8.2
Setting instructions
Operating mode:
Example: SP, Record & Play
Record video signal and play
back section just recorded
Test point: Connection
point for the measuring
instrument (signal)
The element
to be set
TP
ADJ.
Emitter
R3045
7513
TAPE
MEAS. EQ
Oscilloscope,
Blank tape
Video Pattern
Tape required for the
setting work
: 0.001 ~ 50V/Div.
: DC ~ 50 MHz
: 10:1; 1:1
: 0 ~ 50MHz
0310 ±12
Color Bars
40Hz, 3kHz, 15kHz (Mono & Stereo)
Required test signal and
signal input:
Example: White picture
video signal to SCART
input
MODE
INPUT
SP.Record &
SCART-Input
Playback
White picture
SPEC.
1V
pp
±40mV
Generator
Measuring
instrument
Required value
Electrical alignments
8.3
Video signal processing (VS-SEC)
Service tasks after replacement of ICs 7004, 7072:
Before commencing adjustment:
Call the service test program and enter Step 10 (Dummy
mode). Remove the drive from the motherboard.
8.3.1
3.3 MHz adjustment [3089] (for SECAM)
Purpose:
To adjust the mixing oscillator
Consequences of incorrect settings:
Cross patterns in coloured areas, coloured noise.
A: AC, 50mV/Div, 50ns/Div
IC 7072 Pin 17
8.3.2
SECAM chrominance record current adjustment [3088]:
Purpose:
To set the optimum record SECAM chroma level.
Symptom, if incorrectly set:
If the record level is too high, beats may appear on the
picture. If the level is too low, the colour may be degraded.
VR120
8.
PB
GB 91
0V
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