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Power Base-1 & 460CSL Amplifier Service Manual
14
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.
Checkout Procedures
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.