Electrical Adjustment; Xm-754Sx Qq - Sony xm-754sx Service Manual

XM-754SX
QQ
3 7 63 1515 0
Bias Adjustment
Note : The Bias adjustment should be performed only if any of
Q109 and Q110 for RV104, Q209 and Q210 for RV204,
Q309 and Q310 for RV304, and Q409 and Q410 for RV404
are replaced.
Setting :
Stabilized
Power supply
B+,REM terminals
GND terminal
Procedure:
1. Rotate variable resistors RV104 (FRONT L-CH), RV204
(FRONT R-CH), RV304 (REAR L-CH) and RV404 (REAR
R-CH) full counterclockwise as seen from the pattern side to
minimize the bias current.
2. The input signal is with no signal.
3. Connect the stabilized power supply between B+ and REM
terminals and gradually increase the voltage to 14.4 V while
checking for any abnormal current.
4. Adjust RV104 (FRONT L-CH), RV204 (FRONT R-CH), RV304
TE
L 13942296513
(REAR L-CH) and RV404 (REAR R-CH) so that the digital
voltmeter connected between the respective test points reads
19.5±0.5 mV.
RV Ref. No. Test points
RV104 TP11 and TP12
RV204 TP21 and TP22
RV304 TP31 and TP32
RV404 TP41 and TP42
5. After this adjustment, verify that the current value of the
stabilized power supply is 2.5±0.5 A.
(When the set is cool, more current will flow. If the observed
value is out of specification, wait unit the set is warmed up and
then perform this adjustment again.)
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SECTION 3

ELECTRICAL ADJUSTMENT

Digital
Voltmeter
set
+
_
test points
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Adjustment Location :
– MAIN BOARD (CONDUCTOR SIDE) –
RV304
BIAS ADJUSTMENT
(REAR L-CH)
RV404
BIAS ADJUSTMENT
(REAR R-CH)
Test Point Location :
– MAIN BOARD (CONDUCTOR SIDE) –
TP31
TP32
TP33
Q Q
3 6 7 1 3
TP41
TP42
TP43
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2 9 9 4 2 8
RV204
BIAS ADJUSTMENT
(FRONT R-CH)
RV104
BIAS ADJUSTMENT
(FRONT L-CH)
TP22
TP23
1 5 0 5 8 2 9 9 4
TP12
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9 9
TP21
2 8 9 9
TP11
TP13