Maintenance 5-9
130446-1 Rev. A
MA-5002VZ Service Manual
©2000 Crown International, Inc.
With the amplifier powered from a variac, increase
AC mains line voltage to 12% above the line voltage
for which the amplifier is wired. The amplifier should
trip off at 10.5% to 11% above the line voltage for
which it is wired. If it does not, then set line voltage to
10.5% high and slowly adjust R780 on the control
module until the amplifier trips into protect mode. If
adjustment is performed, retest new adjustment.
Place sensitivity switches in 26 dB position; check or
place LOI (EPS) switches to OFF (BYPASS) position.
Insert a 1-kHz sine wave and adjust for 2.8 Vrms
(1 W) output into 8 ohms. Adjust to 30 Hz then to
20 Hz, level should remain constant. Switch LOI (EPS)
to ON (ENABLE). Check output at 30 Hz at –2 dB ±
0.1 dB. Adjust frequency to 20 Hz and measure out-
put level at –11 dB ± 0.1 dB. Return LOI/ESP and
sensitivity switches to initial condition (Section 5.4.1).
With each channel loaded to 8 ohms, insert a 1-kHz
sine wave and increase level until the amplifier is well
into clip. Place the compressor switches in SLOW po-
sition and check for non-clipped output. Move
switches to FAST position and again verify non-clipped
output. Return switches to OFF position.
Place the Stereo/Mono switch in the PARALLEL MONO
position. Load each channel to 8 ohms separately,
(loads must be precisely equal) and insert a 1 kHz
sine wave. Adjust for 60 Vrms output. Measure VAC
of the channel 1 + output with respect to the channel
2 + output. Verify null of less than 100 mVrms with
signal applied. If necessary adjust null via R4 parallel
balance pot on the Main Module. Make sure the Ste-
reo/Mono switch is returned to STEREO upon test
completion.
Factory set adjustment normally will not require
recalibration. Perform this check as a verification,
adjust only if the measurement is out of tolerance. With
channel 1 loaded to 1 ohm, insert a 1 kHz sine wave
and adjust for an output of 10.00 Vrms, ±20 mV. Mea-
sure TP1 pin 1 with respect to ground. Value should
be 2.00 Vrms ±10 mV. If necessary adjust V/A cal pot
R759 on the current sense module. Repeat test for
channel 2 measuring TP2 pin 1; adjust R859 if neces-
sary.
Type of Test Input Signal and Comments
or Adjustment Load Parameters
14. Over-voltage No Signal
No Load
15. LOI Sine Wave
8-ohm Load
16. Compressor 1-kHz Sine Wave
8-ohm Load
17. Parallel Balance 1-kHz Sine Wave
8-ohm Load
18. Current Sense Cal. 1-kHz Sine Wave
1-ohm Load
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