Crown 460CSL TEST 4 AC POWER DRAW, TEST 5 COMMON MODE REJECTION, TEST 6 VOLTAGE GAIN

Power Base-1 & 460CSL Amplifier Service Manual

Checkout Procedures

TEST 4: AC POWER DRAW

Spec: 90 Watts maximum quiescent.

Initial Conditions: Controls per standard.

Procedure: With no input signal and no load, measure AC line wattage draw. If current draw is excessive, check for high AC line voltage or high bias voltage.

TEST 5: COMMON MODE REJECTION

Spec at 100 Hz: –70 dB.

Spec at 20 kHz: –50 dB.

Initial Conditions: Controls per standard.

Procedure: No load. Inject a 0 dBu 100 Hz sine wave into each channel, one channel at a time, with inverting and non-inverting inputs shorted together. At the output measure less than –44 dBu. Inject a 0 dBu 20 kHz sine wave into each channel, one channel at a time, with inverting and non-inverting inputs shorted together. At the output measure less than –24 dBu. Adjust R921 or R1021, if necessary, to obtain the required measurements. (In older units the adjust- ments are done using N100/N200.)

TEST 6: VOLTAGE GAIN

Spec: ±3% when the Sensitivity Switch is set for 26dB gain, ±6% when the Sensitivity Switch is set for 0.775V or 1.4V sensitivity.

Initial Conditions: Controls per standard.

Procedure: No load connected. Inject a 0.775 VAC 1 kHz sine wave with the Sensitivity Switch in the 26 dB position. Measure 15.5 VAC ±0.07 VAC at the ampli- fier output. Inject a 0.775 VAC 1 kHz sine wave with the Sensitivity Switch in the 0.775V position. Measure 39.9 VAC ±1.2 VAC at the amplifier output. Inject a 1.4 VAC 1 kHz sine wave with the Sensitivity Switch in the 1.4V position. Measure 39.9 VAC ±1.2 VAC at the amplifier output. Return the Sensitivity Switch to the 26 dB position.

TEST 7: PHASE RESPONSE

Spec: ±10° at 1 Watt.

Initial Conditions: Controls per standard, 8 ohm load on each channel.

Procedure: Inject a 1 kHz sine wave and adjust for 1 Watt output (2.8 VAC). Check input and output signals against each other, input and output signals must be within 10° of each other.

TEST 8: LEVEL CONTROLS

Spec: Level controlled by level controls.

Initial Conditions: Controls per standard.

Procedure: No Load. Inject a 1 kHz sine wave. With level controls fully clockwise you should see full gain. As controls are rotated counterclockwise, observe similar gain reduction in each channel. When com- plete, return level controls to fully clockwise position.

TEST 9: CURRENT LIMIT

Spec: Current Limit at 13 ±2 Amps

Initial Conditions: Controls per standard.

Procedure: Load each channel to 1 Ohm. Inject a 1 kHz differentiated (or 10% duty cycle) square wave and increase output level until current limit occurs. Current limit should occur at 11 ±1 Amps. Observe clean (no oscillations) current clipping.

TEST 10: SLEW RATE & 10 KHZ SQUARE WAVE

Spec: >13V/µS.

Initial Conditions: Controls per standard.

Procedure: Load each channel to 8 ohms. Inject a 10 kHz square wave to obtain 40 volts peak-to-peak at each output. Observe the slope of the square wave. It should typically measure 17 to 25 V/µS. Also, the square wave must not include overshoot, ringing, or any type of oscillation.

TEST 11: CROSSTALK

Spec: <33 mVAC at 20 kHz.

Initial Conditions: Controls per standard. Short input of channel not driven.

Procedure: 8 ohm load on each channel. Inject a 20 kHz sine wave into the Channel 1 input and increase output level to 37.4 VAC. Measure less than 33 mVAC at the output of Channel 2. Inject a 20 kHz sine wave into the Channel 2 input and increase output level to 37.4 VAC. Measure less than 33 mVAC at the output of Channel 1.

TEST 12: OUTPUT POWER

Spec at 8 Ohm Stereo: 205W at 0.1% THD.

Spec at 4 Ohm Stereo: 230W at 0.1% THD.

Initial Conditions: Controls per standard.

Procedure: Load each channel to 8 ohms. Inject a 1 kHz sine wave and measure at least 40.5 VAC at the output of each channel. Load each channel to 4 ohms. Inject a 1 kHz sine wave and measure at least 30.3 VAC. All power measurements must be at less than 0.1% THD.

TEST 13: REACTIVE LOADS

Spec: No oscillations. Safe with all types of loads.

Initial Conditions: Controls per standard.

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