Adjustment Instructions - Hitachi VTMX900ECT Manuel D'entretien

ADJUSTMENT INSTRUCTIONS

Test equipment:
1. Dual-trace oscilloscope
Voltage range : 0.001 ~ 50 V/div
Frequency : DC ~ 50 MHz
Probe : 10:1, 1:1
2. DVM (Digital voltmeter)
3. Frequency counter
4. Sinus generator
Sinus : 0 ~ 50 MHz
5. Test pattern generator
6. VHS Alignment Tape 4822 397 30103
SPC Alignment Tape 4822 397 30268
VHS-test cassette
Counter Reading Start 0 0040 ±8
Video Blank B&W Pattern
Audio Blank 6kHz (mono)
How to read the adjustment procedures:
tape section
measuring
equipment
component
TP ADJ.
Pin 2 of
R3054 SP . PLAYBACK
Con.1911
(FMRV)
TAPE MEAS. EQ.
Blank Frequency-
Tape
Measuring
equipment
adjustment
0310 ±12
Color Bars
40Hz, 3kHz, 15kHz (Mono & Stereo)
MODE INPUT
SPEC.
3,800MHz
Counter ±10kHz
Specification
1. 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.
1.1 3.3 MHz adjustment [3089] (for SECAM)
Purpose: To adjust the mixing oscillator
Consequences of incorrect settings:
Cross patterns in coloured areas, coloured noise.
TP ADJ. MODE
Dummy mode
IC7072
step 10
R3089
pin 17
playback
TAPE MEAS. EQ.
Oscilloscope
Video pattern
generator
Sinus generator
A: AC, 50mV/Div, 50ns/Div
IC 7072 Pin 17
1.2 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.
TP ADJ. MODE
Dummy mode
CSRP
Record
R3088
pos.9034
Preset E2
TAPE MEAS. EQ.
Oscilloscope
Blank
Video Pattern
Tape
Generator
Notes: With varying frame amplitudes, the setting is made for the
greatest amplitude.
A: AC, 50mV/Div, 20us/Div
Testpoint slider Pos. 3131
2-25
INPUT
1.2 MHz sinus
100mVpp,
wire 9021
(FMPV)
SPEC.
adjust to
optimum
sinus
PB
0V
INPUT
(VIDEO IN E2)
Red Picture SECAM
75% Saturation
SPEC.
A=240 ± 15 mV
pp,
REC
A
GB