Crown CE 2000, Руководство по обслуживанию

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CE Series Service Manual
Rev. D
Field Modifications 9-3
9.3 Modification to correct oscillation/
noise problem
Applicability: CE-1000 and UT-1010 with #102138-8
module, and CE-2000 and UT-2020 with #102140-8
module.
A change was made on main boards 102138-8
(CE1000) and 102140-8 (CE2000) which has been
found to cause the amplifier to exibit an oscillation or
noise in the output under certain specific operating
conditions. This problem applies only to new amplifi-
ers with -8 main boards, or older amplifiers into which
a new -8 main board is being installed.
A modification has been designed to provide better
ground isolation on the input module, preventing the
problem from occuring. All SST input modules (includ-
ing the standard input module) used in the affected
amplifiers should be modified to prevent oscillations
or noise from occuring. Perform the modification as
follows:
Figure 9.2. Standard SST module, component side
Figure 9.3. SBSC module, rear view
Procedure:
1. Dis-attach AC, input and output connections from
the amplifier.
2. Loosen and remove the screws holding the SST
input module in place, and remove the module.
3. Remove the screws holding the front plate of the
module in place, and remove the front the front plate.
4. De-solder capacitors C606 and C607 on standard
SST input module, or capacitors C31 and C32 on SST-
SBSC module. These are 0.1uF surface-mount capaci-
tors located in the bottom right corner of the circuit
board with the component side of the board facing
you on the standard SST module (see Figure 9.2,) and
directly above J2 on the rear side of the circuit board
on the SST-SBSC module (see Figure 9.3.)
5. Replace the capacitiors with 15 ohm, 0.1W surface
mount resistors, Crown part number A11371-1501.
6. Reassemble the module and re-install in the ampli-
fier.