Crown Macro-Tech MA-5002VZ Service Manual page 35

130446-1 Rev. A
WARNING: Many of the following checks are done by connecting a resistive load to the output of the
amplifier. Use caution and follow check-out procedures carefully to ensure correct results. These
tests require a resistive load capable of over 3000 W continuous into as low as 1 ohm.
WARNING: The MA-5002VZ is capable of drawing in excess of 80 Amperes of current from 120VAC
Mains when loaded to 2 ohms per channel and with both channels driven by a 1 kHz sine wave.
CAUTION: 30 A fuses should be replaced after completion of tests, as they will be stessed during high
power tests. Special 30 A test fuses may be used during testing if they are replaced with the stock
fuses after the tests. 30 A fuse part number is A10285-30.
Type of Test
or Adjustment
7. CMR Null
8. Sensitivity (Gain)
9. Bridge Mono
©2000 Crown International, Inc.
Input Signal and
Load Parameters
0.775V (0 dBu), With the sensitivity switch in the high gain position
1-kHz Sq. Wave (0.775V), insert a common mode 1-kHz 0 dBu square
No Load wave into channel 1 (phono tip & ring shorted or XLR
pins 2 and 3 shorted). At the output jacks measure
less than 25 mV. If necessary adjust R105. Repeat
test for channel 2, adjust R205 if necessary. This ad-
justment is easiest when done with an oscilloscope
at the output and adjusting the square wave for a flat
line. (Set scope for high vertical sensitivity.)
1-kHz Sine Wave Set the sensitivity switches to the 26-dB position,
No Load check both level controls full clockwise. Insert a .775V
1-kHz sine wave and measure 14.8V–16.1V at the out-
put of each channel. Set sensitivity to the 0.775V po-
sition and measure 95V–104V at the output of each
channel. Set the sensitivity switches to 1.4V position
and measure 51.8V–57.2V at the output of each chan-
nel.
1kHz Sine Wave
No Load Note: Always turn power to the amplifier off prior to
changing the position of the Stereo/Mono Switch. With
the dual/mono switch in the bridge mono position, set
the channel two input level control to full CCW. Insert
a .775 Vrms 1-kHz signal into channel one input. There
should be signal present on both channel outputs,
equal in amplitude, with channel two 180 degrees out
of polarity from channel one (see Figure 5.2). Chan-
nel one input level control should control the output
level for both channels. Return the amplifier to stereo
operation.
MA-5002VZ Service Manual
Comments
Maintenance 5-7