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Performance Check and Calibration Procedures
5–4
760A / 760D / 760N
c. Return the autotransformer to the local nominal mains voltage.
3. Check Input Termination
a. Disconnect the input from the LEFT AUDIO INPUT.
b. CHECK – that the resistance across pins 2 and 3 of each rear–panel
XLR input is greater than 10k Ω.
c. Set the Input Termination for each AUDIO INPUT to the 600 Ω position
(see Figure 5–1).
d. CHECK – that the resistance across pins 2 and 3 of each input is 600 Ω
"50 Ω.
e. Set the Input Termination for each AUDIO INPUT to the 150 Ω
position.
f. CHECK – that the resistance across pins 2 and 3 of each input is 150 Ω
"20 Ω.
g. Set the Input Termination for each AUDIO INPUT to the INF position.
4. Check Bar Graph Accuracy (0 dB "0.3 dB)
a. Connect the leveled audio signal generator output to the LEFT AUDIO
INPUT.
b. Adjust the signal generator amplitude so that the bar graph’s top green
LED is just lit.
c. CHECK – that the signal generator amplitude is within the following
limits:
760A: 748.7 – 802.1 mV
rms
(775 mV
rms
"0.3 dB)
760D: 531.4 – 569.3 mV
rms
(550 mV
rms
"0.3 dB)
760N: 750.7 – 804.2 mV
rms
(777 mV
rms
"0.3 dB)
d. Set the audio generator output level to:
760A: 308.5 mV
rms
(–8 dB TEST)
760D: 550 mV
rms
(–9 dB arrowhead)
760N: 777 mV
rms
(0 dB TEST)
e. CHECK – the bar level while holding the EXPAND SCALE button in:
760A: –8 dB "0.3 dB (3 segments)
760D: –9 dB "0.3 dB (2 segments)
760N: 0 dB "0.3 dB (3 segments)