Test Procedures; Standard Initial Conditions; Equipment Required - Crown Macro-Tech MA-5002VZ Service Manual

MA-5002VZ Service Manual
Indicator Condition
ODEP Both OFF
SPI/IOC Both ON
I /I Both OFF
LOAD LIMIT
STBY Both OFF
OV/THERM Both OFF
DC/LF Both ON
OUTPUT MOD Both OFF
ODEP One OFF
SPI/IOC Either OFF/ON
I /I Either OFF/ON
LOAD LIMIT
STBY Both OFF
OV/THERM Both OFF
DC/LF Both OFF
OUTPUT MOD One ON
ODEP Both OFF
SPI/IOC Both OFF
I /I Both OFF
LOAD LIMIT
STBY Both OFF
OV/THERM Both OFF
DC/LF Both OFF
OUTPUT MOD Both OFF

5.4 Test Procedures

The following test procedures are to be used to verify
operation of this amplifier. DO NOT connect a load or
inject a signal unless directed to do so by the proce-
dure. These tests, though meant for verification and
alignment of the amplifier, may also be very helpful in
troubleshooting. For best results, tests should be per-
formed in order.
All tests assume that AC power is from a regulated 120
VAC source. Test equipment includes an oscilloscope,
a DMM, a signal generator, loads, and I.M.D. and T.H.D.
noise test equipment.
WARNING! Most adjustments are made with the cov-
ers removed. Prior to any AC power off testing, dis-
charge all power supply capacitors. Also, use ex-
treme caution when making internal adjustments
when the unit is powered.
5-4 Maintenance
Cause
Both ODEP indicators off coupled with both IOC and DC/LF indi-
cations indicates a DC offset at both outputs. If possible, inquire if
the user was operating the amplifier in a mono mode when the
failure occurred. If so, then it is likely that output stage damage
has occurred in both channels. If not, two unique problems may
have occurred, or there may be an unexpected short on the ter-
minator/current sense module. Other unexpected shorts may be
possible. Mechanical integrity should be carefully checked.
An ODEP indicator off coupled with one internal OUTPUT MOD
indicator lit may be accompanied with IOC and I
affected channel. Such a fault is latching and keeps the high volt-
age rails off. This type of fault is caused by conduction in both the
positive and negative half of the output stage simultaneously.
Under normal conditions this cannot occur at levels much above
100mW, assuming the amplifier is properly biased. A fault like this
is usually the result of a failed output device, or possibly a failed
bias network. It may also be caused by operating the amplifier at
extremely high levels with ultra-sonics.
Both ODEP indicators off with no other abnormal indication is al-
most impossible unless both relays fail, or the Power Loss IC
(U111A) circuit has failed.

5.4.1 Standard Initial Conditions

The start of each step assumes all switches are pre-set
to the following positions:
Dual Mono Switch: STEREO position.
Sensitivity Switches: Both to 0.775V position.
Compressor Switches: Both to OFF position.
LOI Switches: Both to OFF position.
VZ Mode Switches: Both to VZ position.
Level Controls: Both up (clockwise) fully.

5.4.2 Equipment Required

The following is a list of standard equipment needed to
perform all the tests listed in Section 2.3.3:
Line Voltage Variac: 5 kW or larger.
Oscilloscope: 2 Channel, 10 MHz or better.
Digital Multimeter: Various measurements.
Watt Meter: For AC line draw.
ACVM: Peak reading RMS calibrated (all AC line
voltage and amplifier output voltage checks).
I.M.D. Analyzer: 60 Hz/7 kHz in 4:1 ratio, accurate to
0.001% I.M.D.
T.H.D. Analyzer: Accurate to 0.001%.
Loads: 3000 W continuous at 1 ohm.
130446-1 Rev. A
/I for the
LOAD LIMIT
©2000 Crown International, Inc.