Marantz Sm-10 - Page 8

ADJUSTMENT
DC offset adjustment
Adjustment: R715 (22 kQ)
Input:
Output: 8Q load
Measuring point: SP. OUT
Connect a digital voltmeter to the SP. out terminals and
adjust R715 until the output voltage is O mV.
Bias current adjustment
. CLASS B (Set the rear panel CLASS A/B selector switch
to CLASS B.)
Adjustment: RNO1 (1 k&2)
Input:
Output: 8Q load
Measuring point: J707 (pins 1 ~ 3)
Connect a digital voltmeter to J707. After the terminal
Voltage stabilizes (approx. 30 ~ 60 seconds later), adjust
RNO1 until the voltmeter reads 27 mV.
_ CLASS A (Set the rear panel CLASS A/B selector switch
to CLASS A.)
Adjustment: RNO2 (4.7 kQ2)
Input:
Output: 82 load
Measuring point: J707 (pins 1 ~ 3)
REQUIRED MEASURING INSTRUMENTS
Table 1. List of required measuring instruments
r
Item
Connect a digital voltmeter to J707. After the terminal
voltage stabilizes (approx. 30 ~ 60 seconds later), adjust
RNO2 until the voltmeter reads 220 mV.
Peak indicator LED adjustment
Adjustment: RX03 (1 kQ2)
Input: 1 kHz
Output: 8Q load
Measuring point: SP. OUT
1) Set the rear panel CLASS A/B selector switch to
CLASS B.
2) Apply the specified input signal to the amplifier input
and adjust the output level control until an output
power of 120 watts (31.0V) is obtained. Then increase
the generator output level further by 1 dB. (The input
voltage is approximately 1.5V.)
3) Adjust RX03 so the power indicator LED’s indicating
120 and 200 watts both light in the same brightness.
Set the rear panel CLASS A/B selector switch to
CLASS A.
Check that the power indicator LED indicates 30 watts
when the amplifier delivers a power of 30 watts into
8Q load.
4
Purpose
Distortion meter
Measures distortion in amplifier output and its voltage.
——r
Audio frequency generator
Signal source for audio-frequency sine and square waves.
Oscilloscope
Waveform analysis and troubleshooting.
VTVM
Voltage and resistance measurement.
T ay (| eS
AC power meter
Monitors amplifier’s primary power consumption.
Voltmeter
Monitors amplifier’s primary supply voltage.
Slidac (0 ~ 140VAC, 10A)
Adjusts amplifier’s primary supply voltage.
Shorting plug
Used to short input jacks for noise prevention.
Output load resistor
(8Q + 0.5%, 250W)
Load to amplifier output (8Q).
Output load resistor
(42. £ 0.5%, 250W)
Load to amplifier output (4Q).