Adjustment Procedures; Signal Gain Control Adjustment; Led Meter Calibration Procedure; Calibrator - ADC Sound Shaper Three Service Manual

ADJUSTMENT PROCEDURES
(1) SIGNAL GAIN CONTROL ADJUSTMENT
EOUIPMENT REOUIREO (See Figure 10)
1. Audio Oscillator
2. AC Voltmeter
3. Calibrator (dB Attenuator)
4. Oscilloscope
NOTE: • Maintain voltage at 120 V AC (UL, C.S.A. and PX) (220/240 V AC for European models).
• Input - INPUT Jack
• Output - OUTPUT Jack
• Set TAPE MONITOR Switch to "OUT".
• Set BY-PASS/EO Switch to "EO".
• Set SIGNAL GAIN Control on Front Panel at center position.
SIGNAL GAIN LED PROCEDURE (See Figure 11)
(2) LED METER CALIBRATION PROCEDURE
Connect LED Meter calibration set-up as shown in Figure 10.
CALIBRATOR: OFF
AC VOLTMETER: 0.3 V Range
AUDIO OSCILLATOR: Frequency - 1 KHz
OUTPUT - 1.5 V min. into ext. 600 rl load.
INT/EXT LOAD SWITCH (if any) - EXT. (Calibrator box to provide
approximately 600 rl load to generator).
FREOUENCY EQUALIZER: Frequency Control - Flat position
Center Frequency Selector switch - Center position
METER switch - IN
BY-PASS/EO - EO
TAPE MONITOR - OUT
LlNE/REC - REC
Left (VR301) - Max. counterclockwise
Right (VR401) - Max. clockwise
Step
1.
Step
2.
Step 3.
Adjust Audio Oscillator output for 1 V at 1 KHz as read on AC Voltmeter.
Set Calibrator at 0 dB. Adjust VR 101 (left) for 1 Volt reading on output AC Voltmeter
and VR 102 (right) for 1 Volt reading on output AC Voltmeter.
Adjust VR201 (left) for both LED's (01002 and 01003) to light with equal intensity
and VR202 (right) for both LED's (01004 and 01005) to light with equal intensity.
METER CONTROL:
Step
1.
CALIBRATION PROCEDURE (Figure 12)
Step
2.
Step
3.
Step 4.
Set Trimmer Resistors on PCB as indicated below:
VRB01, VRB03, VRB05(L)
VRB02, VRB04, VRB06(R): at 12 o'clock position
Adjust Audio Oscillator output for 1BO mV as read on AC voltmeter.
Set Calibrator at 0 dB. Adjust VRB01 (left) for 12 dB on left LED Meter. And VRB02
(right) for 12 dB on right LED Meter. (All LED's are lit.) (Figure 10A)
Set Calibrator at -1 dB point: check that both 12 dB (left and- right) LED's are turned off.
(Figure 10B)
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