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Maintenance 4-9

130485-1 Rev. B

CE 4000 Service Manual

4.6 Electrical Checkout Procedures

The test procedures in this section are used to verify
the operation of the amplifi er. You may, however, fi nd
these tests helpful in troubleshooting a problem if the
problem is not easily identifi ed.

All tests assume that AC power is from 100-240
VAC ±10%.

During each test, it is assumed that the following
conditions are set on the amplifi er unless otherwise
noted:

• Level controls fully clockwise.

• Bridge Output switch off.

• Input Sensitivity of both channels set at 26 dB.

• Filter settings in the back panel are set to FLAT.

4.6.1 Quiescent AC Power Draw

Spec

:130 watts maximum quiescent.

Procedure:

With no load connected to the amplifi er,

turn on the amplifi er. Measure AC power draw. It
should be less than 130 watts.

4.6.2 Gain Switches

Spec:

0.775V, 1.4 V, 26 dB

Procedure:

No Load. With the level controls at full

gain and the input sensitivity switches set to 1.4 V,
inject a 1 kHz, 0.775 Vrms, into each channel. At
the output of each channel measure 38.3 Vrms, ±3.8
Vrms. Switch the Input Sensitivity switches to 26 dB.
At the output of each channel measure 15.5 Vrms,
±0.5 Vrms. Switch the Input Sensitivity switches to
0.775 V, At the output of each channel measure 69.3
Vrms, ±6.9 Vrms.

4.6.3 Bridge Mono Operation

Spec:

Same voltage out both channels, channel 2

out of phase.

Procedure:

No load. Switch the Bridge Mono switch

on and inject a 1 kHz sine wave into channel 1 only.
Monitor both outputs of the amplifi er. They should be
the same voltage and 180 degrees out of phase with
each other. Remove the signal and turn the Bridge
Mono switch off.

4.6.4 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.
Measure 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.

4.6.5 Short Circuit Test

Spec:

Amplifi er 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 amplifi er should cycle
into fault mode. Every four to six seconds the Clip
LEDs will fl ash, indicating that it is checking to see if
the short is still there. Remove the short and perform
the test on channel 2.

4.6.6 Output Power

Spec:

Each channel

600 watts into 8 ohms

1,200 watts into 4 ohms

1,800 watts into 2 ohms (at

≥

200V line voltage).

Spec:

less than 0.5% THD.

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 0.5% THD. Measure at least
69.3 Vrms at the output.

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 0.5% THD. Measure at least
69.3 Vrms at the output.

Procedure 2 ohm:

When testing 2-ohm power at

line voltages under 200 VAC, 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 0.5% THD. Measure at least 60.0
Vrms at the output.

4.6.7 Intermodulation Distortion

Spec:

Less than 0.5% from 0 dB to -30 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 69.3 volts. This is your 0-dB
reference. Measure less than 0.5% IMD from 0 dB to
-30 dB in 5- dB steps.

4.6.8 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.

Terminate 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 550 µVrms at the output
using an A-weighted fi lter.