Block Diagram - Marantz MA-9S1 Service Manual

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 R641
and R642 on the PCB(P641) 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
Insert an adjustment screw driver to the adjustment hole on the cupper cover of the HDAM Q501 on
the PCB P501 and adjust.
• Offset voltage between the SPEAKERS–1 "–" terminal and GND
Insert an adjustment screw driver to the adjustment hole on the cupper cover of the HDAM Q502 on
the PCB P501 and adjust.
Idling Current Adjustment
1. After DC Offset Voltage Adjustment is completed, adjust the idling current with the variable resisters
R641 and R642 on the PCB(P641).
2. Connect a digital voltage meter in between the 1 pin and the 3 pin of J639 and in between the 1 pin
and the 3 pin of J641 each. Connect the 1 pin terminals of J639 and J641 to "+" and the 3 pin to "–".
3. With seeing the digital voltage meter, turn the variable resisters clockwise slowly to adjust the idling
current.
• Idling current adjustment with R641
R641 is to adjust the idling current for the power transistor(s) on the upper side of the heat sink.
Turn R641 clockwise to increase the idling current. The voltage measured by the digital voltage
meter connected to J639 will increase.
• Idling current adjustment with R642
R642 is to adjust the idling current for the power transistor(s) on the lower side of the heat sink.
Turn R642 clockwise to increase the idling current. The voltage measured by the digital voltage
meter connected to J641 will increase.
4. The voltage of the idling current will be 10mV(50mA) for each.
The voltage reaches approx. 12mV(60mA) 3 minutes after turning on power then the voltage decreases
slowly to approx. 10mV(50mA) about 40 minutes after and becomes stable.
Meter Adjustment
1. Connect an oscillator to the input terminal UNBALANCED-1 and connect an AC voltage meter to the
speaker output terminals. ATTENUATOR is set to 0dB and no load is connected to the speaker output.
2. Turn on power and adjust output power (output frequency 1kHz) of the oscillator to set the speaker output
voltage to 49.0V.
3. When the speaker output voltage becomes 49.0V, adjust the variable resistor R917 on the PCB P801
to set the meter 0dB. (Output voltage 49.0V means 300W for 8Ω, 600W for 4Ω.)
4. Assuming this point as 0db, decrease the output power of the oscillator like –10dB ➔ –20dB ➔ –30dB
➔ –40dB, the meter will show the corresponding measurements.
3

4. BLOCK DIAGRAM

UNBALANCED
2 1
3
ATT
INPUT
1
BALANCED
2
ATT
INPUT
SELECTOR
SOFT
START
REGULATOR
I/V
I/V
I/V
I/V
PROTECT
FINAL STAGE
INPUT / DRIVE STAGE
METER / PROTECT
4
SPEAKER
OUTPUT