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Performance Check and Calibration Procedures
760A / 760D / 760N
5–11
Calibration Procedure
1. Preliminary Set Up
NOTE. Unless otherwise stated, always set the Leveled Audio Signal Generator
for a 1 kHz sine wave at the following level:
760A 775 mV
rms
760D 550 mV
rms
760N 777 mV
rms
a. Set the display orientation to X–Y (on A3 Main board, J273 & J373 to
pins 1 & 2). Use the “sound stage” graticule even though the X–Y
orientation is in use. Set the Input Termination (A3 – J192, J392, and
J664) to Inf, and the Input Sensitivity (A3 – J185, J385, and J657) as
shown:
760A 0 dB
760D, 760N U
b. Set the 760A front panel controls as follows:
SELECT AUX
PEAK HOLD OFF
DISPLAY GAIN AUTO
2. Adjust +5 V
a. Connect the DMM negative lead to TP1 (GND) and the positive lead to
W1 (+5V).
b. ADJUST – R99 (+5V ADJ) for +5.0 V "0.5V. See Figure 5–2 for
adjustment locations.
3. Adjust DAC Offset and Gain
a. Connect the digital voltmeter leads to TP248 (DAC output, on A3) and
analog ground (marked A GND).
b. Set S340 (on A3) to Position 5.
c. ADJUST – R253 (DAC offset, on A3) for 0.000 Vdc.
d. Set S340 to Position 4.
e. ADJUST – R252 (DAC gain, on A3) for 5.000 Vdc.
f. Set rotary switch S340 to Position 0 (normal operation).