Alignments; Dc Offset Voltage Adjustment; Idling Current Adjustment - Marantz MA-9S2 Service Manual

3. ALIGNMENTS

Adjustment Procedure
Set the power voltage to rated voltage for this adjustment.

DC Offset Voltage Adjustment

1. Before turning on power, set the attenuator switch (S201)
at –∞, and turn the variable resisters R691 and R692 on
the PWB (P691) counterclockwise to the end.
Insert digital voltage meters between the SPEAKERS–1
"+" terminal on the rear panel and the GND terminal of
C001/C002, and between the SPEAKERS–1 "–" terminal
on the rear panel and the GND terminal of C001/C002.
2. After the all preparation in Step 1 is done, turn on power.
Just after the speaker relays turning on, make the
adjustment to set the offset voltages of the
SPEAKERS–1 "+" terminal and the SPEAKERS–1 "–"
terminal to 0V ± 20mV.
Also, the difference between the offset voltages of the
SPEAKERS–1 "+" terminal and the SPEAKERS –1 "–"
terminal must be within ±3mV.
• Offset voltage between the SPEAKERS–1 "+" terminal
and GND
Adjust the variable resisters R507 on the PWB P501
so that the desired value is obtained.
• Offset voltage between the SPEAKERS–1 "–" terminal
and GND
Adjust the variable resisters R508 on the PWB P501
so that the desired value is obtained.

Idling Current Adjustment

1. After DC Offset Voltage Adjustment is completed, adjust
the idling current with the variable resisters R691 and
R692 on the PWB (P691).
The test point uses the 2pin connectors J675 and J677
on the PWB (P671).
2. Connect a digital voltage meter in between the 1 pin and
the 2 pin of J675 and in between the 1 pin and the 2 pin
of J671 each. No. 2 terminal is "+" of DC range.
3. With seeing the digital voltage meter, turn the variable
resisters clockwise slowly to adjust the idling current.
• Idling current adjustment with R691
R691 is to adjust the idling current for the power
transistor(s) on the upper side of the heat sink.
Turn R691 clockwise to increase the idling current.
The voltage measured by the digital voltage meter
connected to J675 will increase.
• Idling current adjustment with R692
R692 is to adjust the idling current for the power
transistor(s) on the lower side of the heat sink.
Turn R692 clockwise to increase the idling current.
The voltage measured by the digital voltage meter
connected to J677 will increase.
3. ALIGNMENTS
DC
1.
S201 -
R691 R692
SPEAKERS-1 " "
GND SPEAKERS-1 "-"
GND
2.
SPEAKERS-1 " "
0V 20mV
" "
3mV
• SPEAKERS-1 " "
• SPEAKERS-1 " "
1. DC
R691 R692
J675 J677
2.
J671 2
DC
3.
• R691
R691
R691
• R692
R692
R692
2
ATTENUATOR
P691
C001/C002
C001/C002
ON
SPEAKERS-1 " "
" "
GND
P501 R507
GND
P501 R508
P691
P671 2pin
J675 1 2
J675
J677
2