Crown POWER BASE 1 Service Manual download pdf (Page 14)

Power Base-3 & 1400CSL Amplifier Service Manual

TEST 6: VOLTAGE GAIN

Spec 26dB Gain: ±3%.

Spec 0.775V Sensitivity: ±6%.

Spec 1.4V Sensitivity: +12%/–6%.

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 ±0.5 VAC at the amplifier

output. Inject a 0.775 VAC 1 kHz sine wave with the

Sensitivity Switch in the 0.775V position. Measure 65.7

VAC ±3.9 VAC at the amplifier output. Inject a 1.4 VAC

1 kHz sine wave with the Sensitivity Switch in the 1.4V

position. Measure 65.7 VAC +7.8/-3.9 VAC at the

amplifier output. Return the Sensitivity Switch to the 26

dB position.

TEST 7: PHASE RESPONSE

Spec: ±10° from 10 Hz to 20 kHz 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 38 ±3 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 38 ±3 Amps (38 Vpk) with output

device Vce less than 40 Vpk. Observe clean (no

oscillations) current clipping.

Electrical Checkout Procedures

TEST 10: SLEW RATE & 10 KHZ SQUARE WAVE

Spec: >17V/µS.

Initial Conditions: Controls per standard.

Procedure: Load each channel to 8 ohms. Inject a 10

kHz square wave to obtain 65 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: -60dB at 20 kHz.

Initial Conditions: Controls per standard. Terminate

input of channel not driven with 600 ohms.

Procedure: 8 ohm load on each channel. Inject a 20 kHz

sine wave into the Channel 1 input and increase output

level to 62 VAC. Measure less than 62 mVAC at the

output of Channel 2. Inject a 20 kHz sine wave into the

Channel 2 input and increase output level to 62 VAC.

Measure less than 62 mVAC at the output of Channel

TEST 12: OUTPUT POWER

Spec at 8 Ohm Stereo: 540W at 0.1% THD.

Spec at 4 Ohm Stereo: 760W at 0.1% THD.

International 8 Ohm Stereo:International 8 Ohm Stereo:

International 8 Ohm Stereo: 510W at 0.1% THD.

International 4 Ohm Stereo:International 4 Ohm Stereo:

International 4 Ohm Stereo: 680W 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 65.7 VAC at the output

of each channel. Load each channel to 4 ohms. Inject

a 1 kHz sine wave and measure at least 55.1 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.

Procedure Capacitive: Load each channel to 8 ohms in

parallel with 2 µF. Inject a 20 kHz sine wave with 55

VAC output for 10 seconds.

Procedure Inductive: Load each channel to 8 ohms in

parallel with 159 µHenries. Inject a 1 kHz sine wave

with 35.8 VAC output for 10 seconds.

Procedure Torture: Load each channel with the primary

(red and black leads) of a DC-300A transformer (D

5781-6). Inject a 10 Hz sine wave at sufficient output

level to cause 3 to 5 flyback pulses, for 10 seconds.

Procedure Short: Inject a 60 Hz sine wave at 5 VAC

minimum output. After establishing signal, short the

output for 10 seconds.

Out

.047 uF

1K Ohm

Differenciator Circuit

1 2 ... 9 10 11 12 13 14 15 16 17 18 19 ... 26 27

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