Popping Noise Protective Circuit; Led Meter Operating Chart - ADC Sound Shaper Three Service Manual

II
off".
POPPING NOISE PROTECTIVE CIRCUIT
This circuit eliminates the popping noise in the speakers when the power switch is turned "on" or
This circuit consists of TR201, TR202, TR203 and a Reed Relay.
When power is switched "on", -0.5 VDC is provided to the baseof TR201 through R238. TR201
will turn off. After about 6 seconds, TR202, TR203 will turn on. Thus the Reed Relay will restore
connections to the OUTPUT Terminals.
When the power switch is "off", 1.7 VDC is provided to the baseof TR201 through R237. TR201
will turn on, TR202 and TR203 will turn off. And thus the Reed Relay will disconnect the
OUTPUT.
LED METER OPERATING CHART
AC INPUT AT VR301
RECTIFIED DC V LED METER LED METER VOLTAGE ACROSS
(Max. CW)
AT C807 (-) INDICATION CURRENT EACH LED
mV RMS
@
1 KHz
(mA)
DC VOLTS
See NOTE 1.
See NOTE 2. See NOTE 3.
12 mV -53 mV DC -12 dB 2.63 mA 1.84 V DC
15 mV
-76 mV DC -10dB 2.63 mA 1.84 V DC
19 mV
-102 mV DC -8dB 2.63 mA 1.84 V DC
24 mV
-132 mV DC -6 dB 2.63 mA 1.84 V DC
29 mV
-166 mV DC -4dB 2.63 mA 1.84 V DC
35mV
-205 mV DC -2dB 2.63 mA 1.84 V DC
46 mV
-278 mV DC OdB 2.63 mA 1.84 V DC
65 mV
-395 mV DC +2 dB 2.63 mA 1.84 V DC
74 mV -453 mV DC
+4 dB
2.63 mA
1.84 V DC
100 mV
-618 mV DC +6 dB 2.63 mA 1.84 V DC
120 mV
-740 mV DC +8dB 2.63 mA 1.84 V DC
150 mV
-940 mV DC +10 dB
2.63 mA
1.84 V DC
190 mV
-1.18 V DC +12 dB 2.63 mA 1.84 V DC
- 9 -
Rectified DC V and LED Meter data for actual levels used for LED Meter indication. (LED "ON"
condition)
NOTE:
1. AC signal applied to INPUT jacks of Equalizer.
BY-PASS/EO switch to EO, METER switch to IN, LINE/REC to REC and MONITOR to OUT.
2. Rectified DC voltages measured from C807 (-).
3. Indicated voltages across each LED indicator are obtained with LED Meters calibrated as
specified in the CALIBRATOR PROCEDURE section of this manual.
4. All DC voltages are within
±
10%, measured with AC\ VTVM and DC Voltmeter (over 10 Kn/V).
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