dbx 3BX III, Руководство по обслуживанию

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Model 3BX III Service Manual
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7.3.4 Low-Band Tests
7.3.4.1 Set the oscillator to 100 Hz at 0 dBV (1 V rms).
7.3.4.2 Adjust the Transition-Level control for 0 dBV at the
3BX III output.
7.3.4.3 Reduce the oscillator output to –10 dBV (316 mV rms).
7.3.4.4 Verify that the 3BX III output level decreases to
-15 dBV (178 mV rms) ±1 dB.
7.3.4.5 Reduce the oscillator output to –20 dBV (100 mV rms).
7.3.4.6 Verify that the 3BX III output level decreases to
-30 dBV (31.6 mV rms) ±2 dB.
7.3.4.7 Repeat for the other channel.
7.3.5. Mid-Band and High-Band Tests
Repeat the steps in 7.3.4, but use 1 kHz for the mid-band and
10 kHz for the high-band.
7.4 Distortion
7.4.1 Set the unit as follows:
Expansion Minimum
Impact Restoration Minimum
Transition Level Mid-Point
Pre/Post Pre
Source/Tape Source
Bypass Out
(not set)
7.4.2 Connect the sine-wave oscillator to the unit’s left and right
inputs.
7.4.3 Connect the output of one channel of the 3BX III to a
distortion analyser or THD meter.
7.4.4 Low-Band Distortion
7.4.4.1 Set the oscillator to 100 Hz at 0 dBV (1 V rms).
7.4.4.2 Verify that the THD is less than 0.15%.
7.4.4.3 Repeat for the other channel.
7.4.4.4 Now set the Expansion and Impact-Restoration controls
to their maximum positions.
7.4.4.5 Adjust the Transition-Level control for 0 dBV at the
3BX III output.
7.4.4.6 Verify that the THD is less than 0.25%.
7.4.4.7 Repeat for the other channel.
7.4.5 Mid-Band Distortion
Repeat the steps in 7.4.4 using 1 kHz. The first (minimum-
position) THD reading should be 0.15%, and the second 0.2%.
Don’t forget to do the second channel.