3. Connect a distortion analyzer with a resolution of
20-20kHz (or better) to the
output terminals of the amplifier. Enable the 80kHz low pass filter.
4. Connect a dual-channel oscilloscope to the following test points:
Chl - a 1OX (vertical sensitivity - 2V/cm) scope probe to the channel speaker output.
Ch2 - a IX scope probe (vertical sensitivity - 0.
to the distortion analyzer
output.
5. Set amp gain pots fully clockwise and turn on power switch.
6. Connect the output of the signal generator to the input terminals of the amplifier and
select an output of 1.50 VRMS 1 kHz sine wave.
7. Plug the amplifier into a variac and set up an AC line current monitor.
l
POWER UP & MUTE DELAY TEST
CAUTION: To avoid damage to the main printed circuit board, place a 50 ohm 225W resistor (100 ohm,
240VAC) in series with the high (+) lead on the AC cable during variac ramp up. if the switching power
supply has a shorted device at initial power up, this AC resistor pad will help prevent undue damage. After
the amplifier has been fully powered up via the variac, confirm that the amplifier has achieved
stable operation during idle. Remove AC power from the amplifier and disconnect the series
resistor for normal operation. Continue with the test & calibration process.
1. Slowly raise the variac voltage and watch for excessive current draw (line current
greater than 0.5A a.c at 60 Volts).
is
24OV. Pause at 9OVAC
European)
for three seconds until the mute / protect circuit disengages.
Continue to 12OVAC
European).
2.
Verify that the fan is operating at low speed.
3. Turn the power switch off and on a few times to verify the 3 second power-up muting
delay.
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CHANNEL OUTPUT
I. Look for amplified signal on the scope for channel 1. Switch the input signal and scope
to channel 2 and repeat output test. Check for noisy / contaminated gain pots by
observing general instability on the distortion waveform while adjusting the gain control
levels.
2. Select an 8 ohm load and confirm that this amplifier is producing 425 watts at 1 kHz just
below the point of clipping. Check both channels.
l
BRIDGE MODE
1. Turn the power switch off.
2. Set Mode Switch #7 in the on position. The gain control, limiter, and filter switch positions
on CH2 are disabled with Mode Switch #7 on.
3. Set load to both red output binding posts
positive and CH2 negative).
4. Apply a 1.30 VRMS, 1 kHz sinewave input to channel 1 of the amplifier. Check the power
and verify that the output does not immediately collapse. Check for 1500 watts at 8
ohms.
5. Turn power off and place the amplifier under test back into the Stereo mode with output
loads connected to each channel.
l
B I A S
1. Let the amplifier cool down to room temperature.
2. With an input amplitude of 1.5OVrms, increase the input frequency to 2OkHz. Reduce the
input signal 20dB (80%) from full output. Adjust the crossover trimpot VR43
and
VR166 (CH2) for about a 4OOmVpk-pk crossover spike protruding from the noise trace
on the oscilloscope. It will be necessary to have the oscilloscope measure unfiltered
distortion from the amplifier in order to see the crossover spike. It is necessary to
Summary of Contents for PLX Series
Page 2: ... PLX 1202 PLX 1602 PLX 2402 PLX 3002 ...
Page 58: ...H z _ _ _ _ Fi G g u ...
Page 59: ...Q 55 ...
Page 60: ...PLX MAIN MOOULE ASSEMBLY smm 6 20 Y 5 r I_ 1 w ...
Page 81: ... ...
Page 82: ......
