Crown CE 2000, Service Manual

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CE Series Service Manual
Rev. D
LETHAL energy levels! Be very careful when making
connections. Do not attempt to change output wiring until
the amplifier 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 moisture.
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 filter
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 amplifier may draw in
excess of 30 amperes from the AC service mains.
WARNING:
When performing tests in Section 2.3, do not
connect any load to the amplifier until instructed to do so.
There is no danger to the amplifier in operating without any
load (open outputs).
WARNING: Do not change the position of the Mode Switch
when the amplifier 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 amplifier is
plugged in.
CAUTION: When performing tests in Section 2.3 that
require a load, the load must be resistive and must be
capable of handling 1000 W (per channel).
CAUTION: Disconnect the power cord before installing or
removing any cover or panel.
CAUTION ::::: Electrostatic discharge will destroy certain
components in the amplifier. Techicians must have
approved ESD protection. Proper grounding straps and
test equipment are required.
2.3 Troubleshooting
2.3.1 Pre-AC-Checks
A number of checks can be made prior to powering up
the unit. These should be done in order to prevent an
unwanted disaster when turning the unit on. Once these
checks are made, power may be applied for further
checks. Note: It will be necessary to remove the top
panel for complete access to all modules.
2 Maintenance
Fundamentally, troubleshooting involves looking for an
abnormal situation. When a problem has been observed,
it is obvious that something is not doing what it is ex-
pected to do. A single part, solder joint, or trace is usu-
ally the root cause, and testing for typical voltages and
signal tracing can usually result in a solution for most of
the problem units. Unfortunately, there are two other sce-
narios. (1) Sometimes a single problem may cause other
parts to fail so there will be several parts that must be
replaced. In this case, however, finding the root cause is
not as important as just finding all of the blown or dam-
aged parts and replacing them. The failed part will prob-
ably (but not always) be among them and the act of
replacing the parts will fix the amplifier. (2) If the ob-
served behavior is an oscillation, high THD, or the output
slammed to one of the rails, the very nature of a feed-
back amplifier will spread this effect throughout the power
amplifier section. This troubleshooting guide and a fa-
miliarity with amplifier operation should help you fix what-
ever comes your way!
2.1 Surface Mount Technology
The CE-Series amplifiers use surface mount technology
in their design. There are several advantages to using
surface mount technology (SMT), including; (1) surface
mount devices (SMDs) are much smaller, and are
mounted to the surface of the board, so more compo-
nents can be placed on the board. (2) Components can
be attached to both sides of the board, allowing the board
size to be reduced. (3) SMT boards are lighter and pro-
vide better electrical performance signal speed.
Of course, there are also things to watch out for with
SMT. (1) The placement of the components on the board,
not through a hole, makes the components and the sol-
der joint more susceptible to damage. (2) Rework of SMDs
can often require specialized tools, equipment, or train-
ing. (3) SMDs are very small and can be difficult to handle,
see, and identify.
Remember that on the CE-Series amplifiers, the SMDs
on the bottom side of the main module are GLUED. Take
care not to damage components while trying to remove
them from the surface of the module.
2.2 Cautions and Warnings
DANGER:
The outputs of this amplifier can produce
Maintenance 2-1