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1. Clock Frequency Check
Settings:
• Test point: TP2 (CLK IC770 pin30)
Method:
Set to MW 1602kHz and check that the test
point becomes 2052kHz 45Hz (EZ).
2. MW VT Check
Settings:
• Test point: TP1 (VT)
Method:
Set to MW 1602kHz and check that the test
point is less than 8.0V.
Then set to MW 531kHz and check that the
test point is more than 0.6V.
3. MW IF Adjustment
Settings:
• Test point: TP5, TP6
L772 .............................................. 450kHz
4. MW Tracking Adjustment
Settings:
• Test point: TP5, TP6
• Adjustment location: L981
Method:
Set to MW 999kHz and adjust L981 so that the
test point becomes maximum.
5. FM VT Check
Settings:
• Test point: TP1 (VT)
Method:
Set to FM 87.5MHz, 108.0MHz and check that
the test point is more than 0.5V (87.5MHz) and
less than 8.0V (108.0MHz).
6. LW VT Adjustment
Settings:
• Test point: TP2 (VT)
• Adjustment location: L942
Method:
Set to LW 144kHz and adjust L942 so that the
test point becomes 1.3V 0.05V.
Then set to LW 290kHz and check that the test
point is less than 8.0V.
7. LW Tracking Adjustment
Settings:
• Test point: TP5, TP6
• Adjustment location:
L941 .............................................. 144kHz
TC942 ........................................... 290kHz
Method:
Set up TC942 to center before adjustment.
The level at 144kHz is adjusted to MAX by
L941. Then the level at 290kHz is adjusted to
MAX by TC942.
8. DC Balance/Mono Distortion Adjustment
Settings:
• Test point: TP3, TP4
• Adjustment location: L771
• Input level: 54dB
Method:
Set to FM 98.0MHz and adjust L771 so that
the voltage between TP3 and TP4 becomes
0V 0.04V.
Next, check that the distortion is less than
1.3%.
PRACTICAL SERVICE FIGURE
< TUNER SECTION >
< FM SECTION >
IHF Sensitiviy:
(THD 3%)
Distortion:
Stereo separation:
Intermediate frequency:
< MW SECTION >
Sensitivity:
(S/N 20dB)
Distortion:
< LW SECTION >
Sensitivity:
71
Less than 13dB
(at 108.0/98.0MHz)
Less than 14dB
(at 98.0MHz)
Less than 1.2% (98.0MHz)
More than 12dB (98.0MHz)
10.7MHz
Less than 60dB (at 600kHz)
Less than 58dB
(at 1000/1400kHz)
Less than 1.5%
(at 1000kHz)
Less than 70dB (at 144kHz)
Less than 68dB (at 198kHz)
Less than 66dB (at 290kHz)
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