Crown Com-Tech CT-800 Service Manual page 15

Com-Tech 800 Amplifier Service Manual
Electrical Checkout Procedures
Test 18: Intermodulation Distortion
Spec at 0 dB output: 0.01%.
Spec at -35 dB output: 0.05%.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a
SMPTE standard IM signal (60 Hz and 7 kHz sine wave
mixed at 4:1 ratio). Set the 60 Hz portion of the sine
wave to 38 volts RMS. Set the 7 kHz portion to 25%.
With an IM analyzer measure less than 0.01% IMD.
Repeat test at -35 dB (reference 38 volts RMS, 60 Hz
portion) and measure less than 0.05% IMD.
Test 19: Clipping
Spec: No protective action during test.
Initial Conditions: Controls per standard.
Procedure: Load each channel to 8 ohms. Inject a 1 kHz
sine wave into each input and drive the output 6 dB
into clip for 10 seconds. The amplifier should not
activate any protective circuits (ODEP, Fault, or LF
Protection).
Post Testing
After completion of testing, if all tests are satisfactory,
the amplifier controls should be returned to the posi-
tions required by customer. If conditions are unknown
or unspecified, factory settings are as follows:
Level Controls: 9 to 11 O'Clock.
Sensitivity Switch: 0.775V 8/4 Ohm.
Stereo/Mono Switch: Stereo.
70-V Mode Switches: 8/4 Ohm position.
Power: Off
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