Secam Band 1 - Afc Adjustment [3730]: (Secam L / L' Only) - Hitachi VTMX900ECT Manuel D'entretien

2-26
2. Front End (FV)
Service tasks after replacement of IC 7705, coil L5702 and TUMOD:
2.1 AFC Adjustment:
Purpose: Correct adjustment of demodulator AFC - circuit
Symptom, if incorrectly set:
Bad or disturbed TV channel reception.
2.1.1 PAL - AFC adjustment [5702]:
TP ADJ. MODE
IC 7705
Pin 17
L5702 E to E
(AFC
TP9719)
TAPE MEAS. EQ.
DC Voltmeter
Frequ. Generator
2.1.2 SECAM band 1 - AFC adjustment [3730]:
(SECAM L / L' only)
Before commencing adjustment:
- Switch to a band 1 SECAM L' preset.
- Is the system switch, in the menu 'MANUAL SEARCHING', not
possible, press the right cursor key of the remote in the
'CHANNEL NUMBER' line for a short moment.
- A fine-tuning will be done and the system will switch to the
'AUTO' function.
TP ADJ. MODE
E to E,
IC 7705
pin 17
SECAM L' tuned
R3730
(AFC
on this preset
TP9719)
TAPE MEAS. EQ.
DC Voltmeter
Sinus Generator
2.2 HF - AGC adjustment [3707]:
Service tasks after replacement of ICs 7705, or TUMOD:
Purpose: Set amplifier control.
Symptom, if incorrectly set:
Picture jitter if input level is too low and picture distortion
if input level is too high.
TP ADJ. MODE
Tuner
1701
Set tuned to
R3707
Pin 17
channel 27
(TP9713,
ZF-out)
TAPE MEAS. EQ.
Oscilloscope
Video Pattern
Generator
GB
2.3 Attenuating the 40.4 MHz [5704]:
Service tasks after replacement of coil 5704:
Purpose: To attenuate the band I carrier rests.
Symptom, if incorrectly set:
INPUT
38,9MHz 500mV
pp
at Tuner 1701 Pin 17
(TP9713,ZF-out)
SPEC.
2,5V ±0,2V
If the adjustment is correct the signal at pin 1 of SFW [1704] must be
smaller than the input signal amplitude by at least 5 dB.
3. Deck electronics (DE)
Service tasks after replacement of IC 7463:
3.1 Motor frequency - adjustment [2492]:
Purpose:
Result of an incorrect adjustment:
INPUT
Before commencing adjustment:
33,9MHz 500mV
pp
- bring VCR in to EJECT state
at Tuner 1701, pin 17
- disconnect set from main power source
(TP9713, ZF-out)
- remove cable 8004 from connector 1948
- connect test point DRUM [9417] with 5VS1 [9869] (wires
SPEC.
- reconnect to main power source
2,5V ±0,2V
Connector
INPUT
4,5mV(74dBµV)
on aerial input
PAL white picture,
audio IF on,
no modulation
SPEC.
550mV +/-50mV
pp
(use a 10:1 probe )
(SECAM only)
Bad picture quality when the filter attenuates the picture
carrier (38.9MHz).
TP ADJ. MODE
OFW
E to E
1704
L5704
Pin 1
TAPE MEAS. EQ.
Oscilloscope,
Sinus Generator,
Counter
To adjust the working frequency of the head motor driver.
Head motor doesn't start correctly.
on component side)
TP ADJ. MODE
EJECT
1948
C2492
Pin 1
TAPE MEAS. EQ.
Oscilloscope,
Counter
2e
A: DC, 5V/DIV, 50ms/Div
Connector 1948 PIN1-3
153.6 ms = 6e
INPUT
40.4 MHz, 300mV
at Tuner 1701 Pin 17
(TP9713,ZF-out)
SPEC.
adjust minimum
amplitude
INPUT
SPEC.
153,6 ms ±1,5ms
see Diagram
0V
1e 2e 1e
rms