Marantz 250 - Meter Operation and Description; AC Voltage Conversion (100;220 V)

CHANNEL A
AUDIO OUT
METER DESCRIPTION
Overall am
eter R430.
Audio from the amplifier output terminals is applied 0 dB = 0.7!
to METER RANGE switch S2, which selects as a is in the 0
reference two different power output levels: 0 dB =
0.75W or 0 dB = 75W. Meter cali
METER R
Output from the range switch is applied to the ing potenti
input stage (Q403) of the meter drive amplifier. 0 dB = 75
Two diodes (CR411, CR412) limit excessive voltage DC feedbac!
spikes from reaching the input stage. * by R426.
The output stage (Q404) drives a bridge rectifier Zener diod
circuit (CR415, CR416, CR417, CR418) which age for the
generates DC power for the VU meter (M2). Two
zener diodes (CR413, CR414) connected back-to- *NOTE:
back protect the meter and rectifier circuits from 89 load.
possible overload. 82 load.
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100220-V0
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Sa
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220-VOLT
AC
CONV
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To
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B. 250 Metering Circuit Simplified Diagram
perform the following}
1. Remove the top
2. Orient the Mode
facing toward the
Locate TB1, the|
transformer half
which terminate:
mary wires.
Unsolder the big
wires and all jur;
3.