K Series Service Manual Rev A.
5-10 Maintenance
©1999 Crown International, Inc.
5.5.5 Frequency Response
Spec: ±0.25 dB from 20 Hz to 20 kHz.
Procedure: Load the channel under test to 4 ohms.
Inject a 0.1Vrms, 1kHz sine wave into the input. Mea-
sure the output voltage. It should be 2.0 Vrms. This is
now your 1 kHz reference voltage. Switch the frequency
to 20 Hz and verify that the input voltage is still 0.1
Vrms. Measure the output voltage. It should
be the same as the 1 kHz reference voltage ±0.25 dB.
Switch the frequency to 20 kHz and verify that the input
voltage is still 0.1 Vrms. Measure the output voltage and
compare it to the 1 kHz reference voltage. Tolerance is ±0.25
dB. Remove the load and signal. Note: Many oscillators
need a frequency check at 20 kHz.
5.5.6 Short Circuit Test
Spec: Amplifier will protect itself
Procedure: Inject a 1kHz, 1Vrms sine wave into the input of
channel 1. Short the output of channel 1 to ground for 10
seconds. The amplifier should cycle into fault mode. Every
two seconds the Clip and IOC lights will flash, indicating
that it is checking to see if the short is still there. Remove the
short and perform the test on channel 2.
5.5.7 Output Power
K1 Spec: Each channel 350 watts into 8 ohms
550 watts into 4 ohms
750 watts into 2 ohms
K2 Spec: Each channel 475 watts into 8 ohms
800 watts into 4 ohms
1250 watts into 2 ohms
Measure less than 0.1% true THD.
K1 Procedure 8 ohm: Load the channel under test to 8
ohms. Inject a 1kHz sine wave and bring the level up until
the output reaches 0.1% TRUE THD. Measure at least 52.9
Vrms at the output.
K1 Procedure 4 ohm: Load the channel under test to 4
ohms. Inject a 1kHz sine wave and bring the level up until
the output reaches 0.1% TRUE THD. Measure at least 46.9
Vrms at the output.
K1 Procedure 2 ohm: Due to the duty cycle of a test signal,
the line fuse will blow if both channels are tested at the
same time. When testing 2-ohm power, test one channel at
a time. Load the channel under test to 2 ohms. Inject a 1kHz
sine wave and bring the level up until the output reaches
0.1% TRUE THD. Measure at least 38.7 Vrms at the output.
K2 Procedure 8 ohm: Load the channel under test to 8
ohms. Inject a 1kHz sine wave and bring the level up until
the output reaches 0.1% TRUE THD. Measure at least 61.6
Vrms at the output.
K2 Procedure 4 ohm: Load the channel under test to 4
ohms. Inject a 1kHz sine wave and bring the level up until
the output reaches 0.1% TRUE THD. Measure at least 56.6
Vrms at the output.
K2 Procedure 2 ohm: Due to the duty cycle of a test signal,
the line fuse will blow if both channels are tested at the
same time. When testing 2-ohm power, test one channel at
a time. Load the channel under test to 2 ohms. Inject a 1kHz
sine wave and bring the level up until the output reaches
0.1% TRUE THD. Measure at least 50.0 Vrms at the output.
5.5.8 Intermodulation Distortion
Spec: Less than 0.2% from 0 dB to -35 dB.
Procedure: Load the channel under test to 8 ohms. Inject a
SMPTE standard IM signal (60 Hz and 7 kHz mixed at 4:1).
Adjust the output voltage for a peak equivalent voltage of
60.0 volts (K1) or 70.0 volts (K2). This is your 0-dB refer-
ence. Measure less than 0.2% IMD from 0 dB to -35 dB in 5-
dB steps.
5.5.9 Signal to Noise Ratio
Spec: Greater than 100 dB below rated 8 ohm power, A
weighted.
Procedure: Load the channel under test to 8 ohms. Termi-
nate the input with 600 ohms. Verify that the gain switch is
set at 26 dB and level control is at full volume. Measure less
than 529 µVrms (K1) or 616 µVrms (K2) at the output using
an A-weighted filter.
Note: Due to the power conservation circuit you only have 6
seconds to do this test after a signal is injected. After a
signal is used, quickly remove the signal and measure Sig-
nal to Noise.
5.5.10 Crosstalk at 1 kHz
Spec: Greater that 90 dB.
Procedure: Load each channel to 8 ohms. Verify that both
gain switches are set at 26 dB and both level controls are at
full volume. Inject a 2.5 Vrms, 1 kHz, sine wave into channel
1 and terminate channel 2 with 600 ohms. Measure less
than 1.58 mV at the output of channel 2. Now remove the
signal from channel one and inject it into channel 2. Termi-
nate channel 1 with 600 ohms. Measure less than 1.58 mV
at the output of channel 1.
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