Sony MHC-6800 Service Manual page 89

RF PLL Free-run Frequency Check
Procedure :
1. Connect frequency counter to test point (PCK) with lead
wire.
€D board frequency counter
TP(PCK) rae
2. Turn Power switch on.
3. Confirm that reading on frequency counter is 4.3218MHz.
Focus/Tracking Gain
This gain has a margin, so even if it is slightly off.
There is no problem.
Therefore, do not perform, this adjustment.
TUNER SECTION
Precautions in Repairing
@FM SECTION
FM Discriminator Adjustment (NULL Adjustment)
Setting :
BAND: FM
FM RF stereo signal
generator
Carrier frequency : 98MHz
Modulation: 1kHz, 75kHz
deviation (100%)
Output level: ImV (60dBy)
FM ANTENNA terminal
VOM
TP51 (DC range)
NULL terminal
Procedure :
1. Tune the set to 98MHz.
2. Adjust IFTS51 for 0V reading on the VOM.
Note: FM Tuning Level adjustment should be made after
FM discriminator alignment.
FM Tuning Level Adjustment
Setting:
BAND: FM
FM RF stereo signal
generator
759 coaxial
Carrier frequency: 98MHz
Modulation: 1kHz, 75kHz
deviation (1009)
Fl TENN) inal
Output level: 0.018mvV (25dBy)
SECRTENN
feeoniy
Procedure :
1. Tune the set to 98MHz.
2.
Adjust RV52 so that the TUNED indicator goes on.
@ AM SECTION
AM Tuning Level Adjustment
Setting :
BAND: MW
Loop antenna B
Loop antenna A
AM RF signal
generator
Carrier frequeny: 999kHz
30% amplitude
modulation by 400Hz signal
Procedure :
1.
Set loop antenna A so that the loop antenna B input level
becomes 58dBy/m (0.8m V/m)
2. Tune the set to 999kHz.
3. Adjust the RV51 so that the TUNED indicator goes on.
Setting:
BAND: SW
Procedure :
1. Connect digital voltmeter to front end FE1 pin © (VT)
and ground.
2. Adjust for a following value reading on digital voltmeter.
Set frequency | Adiustment | Reading on
' h a s pags part _ | digital voltmeter
f min. 5.95MHz T2 0.9 to 11V.
f max. 17.9MHz cv2 8.3 to 8.7V