Maintenance; Where To Begin; Surface Mount Technology; Disassembly For Inspection & Service - Crown CE-4000 Service Manual

130485-1 Rev. B

4 Maintenance

4.1 Where to Begin

Effective repair involves three basic steps:
1) Determine the symptom(s) of the problem
2) Identify the cause(s) of the symptom(s)
3) Repair the unit to eliminate the cause(s).
To determine the symptoms, you will want to get as
much information from the user as possible. Get
as much information as you can about the system
and how the amplifi er is used. There is always the
possibility that the problem will show up only if used
in a specifi c way.
Once you have all the information about the
symptom(s), it is time to inspect the amplifi er. A careful
visual inspection is valuable for most problems,
which you may encounter. To inspect the inside
of the amplifi er remove the cover as described in
Section 4.3.1.
Begin the inspection by looking for anything, which
appears abnormal, like loose connectors, broken
wires and burnt or visibly damaged components.
Inspect the printed circuit assemblies for broken
traces and loose connections. Be thorough. The
time you spend visually inspecting the amp is time
well spent.

4.2 Surface Mount Technology

CE Series amplifi ers 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 components 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 provide better electrical
performance and signal speed.
WARNING
Amplifi er components are ESD sensitive. When
servicing the amplifi er, the technician must have
approved ESD protection. Proper grounding straps
and test equipment are required. Failure to use
proper protection will result in component failure.
©2002 Crown Audio, Inc.
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 solder joint more susceptible to damage. (2)
Rework of SMDs can often require specialized tools,
equipment, or training. (3) SMDs are very small and
can be diffi cult to handle, see, and identify.
Remember that on the CE-Series amplifi ers, 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.
4.3 Disassembly for Inspection & Service
The extent of disassembly required will depend upon
the extent of inspection and service required.
Note: To avoid the risk of electric shock, turn off
and unplug the amplifi er from the ac power outlet
before disassembly or reassembly is attempted.

4.3.1 Top Cover Removal

To remove the cover of the amplifi er you will need
a #15 torx bit (TX15). After the cover is removed,
and before any internal cables are disconnected,
discharge the supplies. See Section 4.3.2.
1. Turn the amplifi er on its bottom on your workbench.
The only access to the inside of the amplifi er is the
top cover.
2. Using the TX15 bit, Loosen the 8 screws around
the perimeter of the cover.
3. The cover lifts up and back after the screws are
removed.

4.3.2 Power Supply Discharge

Before any connectors and PWAs (Printed Wire
Assemblies, or circuit boards) are removed, the
Power Supplies need to be discharged. Follow these
simple steps.
1. Make sure the amplifi er is unplugged from the
AC power source.
2. Locate L6 and L9 on the Main PWA (see Figure
4.3).
WARNING
Before unplugging or plugging in any connectors
or wires in the amplifier, discharge the power
supplies. See section 4.3.2 for instructions. Failure
to do so will result in circuit failure.
CE 4000 Service Manual
Maintenance 4-1