Maintenance 5-5
130446-1 Rev. A
MA-5002VZ Service Manual
©2000 Crown International, Inc.
Type of Test Input Signal and Comments
or Adjustment Load Parameters
WARNING:
Do not connect any load to the MA-5002VZ power amplifier during these tests
until specifically instructed to do so.
Check for a delay of approximately 4 seconds from
the time the power push button is pressed until the
IOC indication clears and ODEP indicators come on.
If the IOC fails to clear in one channel, check for pres-
ence of rail voltages and for a DC offset. Also check
circuit board LED for indication of a fault - DC/LF,
Output Module, and OV/TSW. Turn unit off, discon-
nect the power cord, discharge power supplies, and
check for a failure in the output stage of the affected
channel, or other applicable circuit area. If the fans
lock in high speed after delay times out, check fan
control components, ODEP output, and LM334Z de-
vices on the output modules.
With the input level controls turned fully clockwise,
the DC offset for both channels should be less than
±15 millivolts.
Note: There are no output offset adjust-
ments for the
MA-5002VZ.
A small DC offset may in-
dicate an ODEP failure. A large DC offset usually indi-
cates a failure in the output stage, though such an
offset should have shut down the amplifier on a DC/
LFI signal.
While there is no published specification on quies-
cent power, it should be checked. A power draw with
the fans off or operating slowly will normally be less
than 150 W (<1.5 A).
If quiescent power greatly ex-
ceeds expectation then turn the amplifier off immedi-
ately and search for power supply or output failure. If
quiescent draw exceeds expectation by a “small”
amount check bias immediately.
Bias voltage is set while the amplifier is at room tem-
perature. If the amplifier is hot from prior testing for
repair or other purposes, it should be set aside until it
has cooled before continuing with this check. Bias,
once factory set, normally will not require adjustment.
For channel 1: Measure the voltage at TP1 pin 2 with
respect to pin 4 (DO NOT measure from ground refer-
ence). The bias voltage should equal .330VDC ± 10
millivolts. If the bias voltage needs to be adjusted,
adjust R505 on the channel 1 output assembly for the
correct bias voltage. For channel 2: Measure the volt-
age at TP2 pin 2 with respect to pin 4 (DO NOT mea-
sure from ground reference). The bias voltage should
equal .330VDC ± 10 millivolts. If the bias voltage needs
to be adjusted, adjust R505 on the channel 2 output
assembly for the correct bias voltage.
1. Turn-on Delay No Signal
No Load
2. DC Output Offset No Signal
No Load
3. Quiescent Power No Signal
No Load
4. High Side Bias No Signal
No Load
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