Disassembly; Electrical Adjustment; Idling Current Adjustment; Side Plate,Sub 1/Sub 2 And Filter Board - Sony XM-7557 Service Manual

DISASSEMBLY

Note: Follow the disassembly procedure in the numerical order given.

3-1. SIDE PLATE,SUB 1/SUB 2 AND FILTER BOARD

1 Three screws
(BTP3x8)
2 Three screws
(BTP3x8)
!ª Screw (BTP3x8)
@º Sub 2 board
@¡ Sub 1 board
@§ Fan motor block
@¢ Screw (BTP3x8)
@∞ TR board
0 Side plate (R)
8 Three screws
(BTP3x8)
@£ CNP708 (2P)
@™ CNP803 (3P)

3-2. AMPLIFIER/POWER BOARD AND LED BOARD

!¡ Six screws
2 Four screws
(P4x40)
!£ Sub heat sink
(Amplifier)
0 Screw (BTP3x8)
9 Four screws
(P3x10)
8 Two screws
(P3x14)
!™ Three screws
(P3x6)
!¢ Two insulating sheets
(AMP)
!∞ Two screws
(P2x10)
!§ LED board
!¶ LED holder
SECTION 3
4 Bottom plate
3 Two screws
(BTP3x8)
!§ Filter board
!∞ Screw (BTP3x8)
5 Three screws
(BTP3x8)
!¢ Auto fuse
!™ Screw (M4)
!£ Cover
!¶ CNP710 (10P)
!• Screw (BTP3x12)
9 Screw (BTP3x8)
!¡ Screw (M4)
3 Six screws
(BVTP3x14)
(P3x10)
4 Two Retainers
5 Two screws (BVTP3x10)
6 Power board
7 Amplifier board
1 Five screws
(BTP3x12)

IDLING CURRENT ADJUSTMENT

• Perform adjustments in the HI-VOLTAGE mode.
1 Adjustment point
Semi-fixed resistors VR101, VR201, VR301, VR401, VR501,
VR502 of amplifier board
2 Precautions on adjustments
1. Set the RCA input terminal to open.
2. Apply a voltage of 14.4V between the +12V terminal, REMOTE
terminal, and GND terminal.
3. Rotate the above semi-fixed resistors completely in the counter-
clockwise direction while observing the component side.
4. Check that the voltage at the adjustment point becomes 0 mV in
7 Side plate (L)
step 2.
5. Fine adjustments may be required according to the characteris-
tics of the MOS-FET used.
• When adjusting the idling current
Rotating the semi-fixed resistor in the clockwise direction:
Increases the idling current
6 Screw (BTP3x8)
Rotating the semi-fixed resistor in the counterclockwise direction:
Decreases the idling current
(F901 to F904) * Take note that rotating excessively in the clockwise direction
will increase the idling current suddenly.
3 Approximate adjustment values
Adjust as follows so that the following voltages become
1.2 to 0.3 mV around 0.7 mV .
FL channel :
Voltage between TP7 and TP6: Use VR101 of the amplifier board
FR channel :
Voltage between TP7 and TP5: Use VR201 of the amplifier board
RL channel :
Voltage between TP7 and TP4: Use VR301 of the amplifier board
RR channel :
Voltage between TP7 and TP3: Use VR401 of the amplifier board
SUBWOOFER Channels :
First, adjust so that the voltage between TP1 and TP2 becomes
1.2 to 0.3 mV around 0.7 mV using VR501 of the amplifier
board.
Next, adjust so that the voltage between TP1 and TP2 becomes
2.4 to 0.6 mV around 1.4 mV using VR502 of the amplifier
board."
Connection :
TP7
TP1
(SUB WOOFER) TP6 (FL-CH)
TP5 (FR-CH)
TP4 (RL-CH)
TP3 (RR-CH)
TP2 (SUB WOOFER)
TP1 (SUB WOOFER)
7 7
SECTION 4

ELECTRICAL ADJUSTMENT

Adjustment Location
– AMPLIFIER BOARD – (Component side)
Digital voltmeter
JW307
JW230
TP7
TP5 TP4
TP6
VR201
VR101 VR301
TP2
TP3
TP1
VR401 VR502
VR501