Crown D-150 - Checkout Procedure - 10 Khz Square Wave Input; Checkout Procedure - IM Intermodulation) Distortion Test; Checkout Procedure ~ 20-20 Khz. Hunvand.noise Test

FIGURE 5-2.
TYPICAL PROTECTION CLIPPING, 2-OHM LOAD
5.7.7 Checkout Procedure — 20 KHz
1. Set the signal generator at 20 KHz at the amplifier input with an »
8-ohm load connected to the amiptifier output.
2. Turn the level control up.until clipping occurs: Clipping must
take place above 85 watts (typically in the 95-100 watt range).
* Refer to Figure 5-3 for duitpuit Waveforit Characteristics.
NOTE:
The.output must.clip before it distorts elsewhere, The dotted
fine in Figure'5-3 shows typical unacceptable distortion on the
leading edges of the waveform.
FIGURE 5-3.
TYPICAL 20KH2z SINE WAVE TEST OUTPUT WAVEFORM
5.78. Checkout Procedure — 10 KHz
Square Wave input
This test is designed to.critically examine the frequency response
and. rise time of the arnplifiér to show how fast the amplifier can
follow rapid signal changes.
1. Set the signal generator for a 10 KHz square wave, 20V p-p at
the amplifier input.
2, Connect an 8-ohm load to the amplifier output.
3.-Turn-up the level control to maximum.
4, The output waveform (Refer to Figure 5-4) should be clean and
sharp throughout the entire range of the level control.
5.7.9 Checkout Procedure -~ IM (intermodulation)
Distortion Test
.
Use
the
IM
distortion
test
setup
shown
in
Figure
5-1.
. Calibrate the IMA and set up the IM input signal at 60-7 KHz,
4:1 ratio as described in the IMA manual.
3. Connect an 8-ohm load to the amplifier output.
Sa ol
4. Measure the IM distortion at 5 dB intervals from 75 watts out-
put
to
7.5
milliwatts
output
as
shown
below.
Ail
distortion
readings must be less thary 0.01%.
BOTH RIGHT AND LEFT CHANNELS
0 % | 78Wout 0 % 237MW
0 % 237Wout 0 % 75 MW
0% | 7 5Wout 0 % 237MW
0 % 23Wout 0 % 7.5MW
0 % .75Wout
syMeTOM PROBABLE CAUSE AND REMEDY.
Sani ttt a
High IM distortion (Ci. defective. Replace.
Change transistor, 04.
Change routing of leads from
from Main PC board to output
transistors and the output ~
binding. posts.
FIGURE 5-4.
TYPICAL 10 Kir SQUARE WAVE TEST OUTPUT WAVEFORM
§.7.10 Checkout Procedure — 20-20 KHz
Hum and Noise Test
Use the noise test setup shown in Figure 5-1.
. Remove input from the amplifier.
Set level controls at minimum (CCW).
. Set AC voltmeter to 100 micravott scale.
Measure the noise level relative to 75 watts into 8 ohms. The
humand noise level must be 115-dB or greater below the tull 75
watt output power. A typical value is -118 to -122 dB.
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