Maintenance; Cautions And Warnings; General Information; Test Procedures - Crown Macro-Tech MA-3600VZ Service Manual

130366-1 Rev. A

4 Maintenance

4.1 Cautions and Warnings

DANGER: The outputs of this amplifi er can produce
LETHAL energy levels! Be very careful when making
connections. Do not attempt to change output wiring
until the amplifi er has been off at least 10 seconds.
WARNING: This unit is capable of producing high
sound pressure levels. Continued exposure to high
sound pressure levels can cause permanent hearing
impairment or loss. User caution is advised and
ear protection is recommended when using at high
levels.
WARNING: Do not expose this unit to rain or mois-
ture.
WARNING: Only properly trained and qualified
technicians should attempt to service this unit. There
are no user serviceable parts inside.
WARNING: When performing service checks with
the power off, discharge the main power supply fi lter
capacitors fully before taking any measurements
or touching any electrical components. A 300-ohm
10-W resistor is recommended for this. Hold the
resistor with pliers, as the resistor may become
extremely hot.
WARNING: Under load, with a sine wave signal
at full power into both channels, the amplifi er may
draw in excess of 30 amperes from the AC service
mains.
WARNING: Do not change the position of the Mode
Switch when the amplifi er is turned on. If the position
of this switch is changed while the amplifier is
powered, transients may damage your speakers.
WARNING: Heatsinks are not at ground potential.
Simultaneously touching either heatsink and ground,
or both heatsinks will cause electrical shock.
CAUTION: Eye protection should be worn at all
times when protective covers are removed and the
amplifi er is plugged in.
CAUTION: Disconnect the power cord before install-
ing or removing any cover or panel.

4.2 General Information

The following test procedures are to be used to verify
operation of this amplifi er. DO NOT connect a load
or inject a signal unless directed to do so by the
procedure. These tests, though meant for verifi cation
and alignment of the amplifier, may also be very
helpful in troubleshooting. For best results, tests
should be performed in order.
©2000 Crown International, Inc.
All tests assume that AC power is from a regulated
AC source appropriate for the unit under test.. Test
equipment includes an oscilloscope, a DMM, a signal
generator, loads, and I.M.D. and T.H.D. noise test
equipment.

4.3 Test Procedures

4.3.1 Standard Initial Conditions
Level controls fully clockwise.
Stereo/Mono switch in Stereo.
Sensitivity switch in 26 dB fi xed gain position.
Ambient Temperature: 20 to 30 degrees C.
It is assumed, in each step, that conditions of the
amplifier are per these initial conditions unless
otherwise specifi ed.
4.3.2 Test 1: DC Offset
Spec: 0 VDC, ±5 mV.
Initial Conditions: Controls per standard, inputs
shorted.
Procedure: Measure DC voltage at the output
connectors (rear panel). There is no adjustment for
output offset. If spec is not met, there is an electrical
malfunction. Slightly out of spec measurement is
usually due to U104/U204 out of tolorance.
4.3.3 Test 2: Output Bias Adjustment
Spec: 310 ±10 mVDC.
Initial Conditions: Controls per standard, heatsink
temperature less than 40°C.
Procedure: Measure DC voltages on the output PWA
across R02, adjust R26 if necessary. Measure DC
voltages on the output PWA across R21, adjust R23 if
necessary. Repeat for second channel.
4.3.4 Test 3: ODEP Voltage Adjustment
Spec: Bias Per Chart, ±0.1V DC.
Initial Conditions: Controls per standard, heatsink
at room temperature 20 to 30°C (68 to 86°F). Note:
This adjustment should normally be performed
within 2 minutes of turn on from ambient (cold)
conditions. If possible measure heatsink temperature,
if not measure ambient room temperature. Use
this information when referencing the chart on the
following page.
MA-3600VZ Service Manual
Mantenance 4-1