Bose FreeSpace Business E4 II Series Service Manual page 74

5.6 Slide the heatsink/PCB assembly for-
ward while lifting the front of the PCB up
slightly.
5.7 Disconnect the fan harness from the
bottom PCB assembly and lift the heatsink
assembly out of the chassis. Disconnect the
power transformer from the lower amp PCB.
Note: Refer to Figures 2 and 4 for the
following procedures.
Transistor Clips
PCB Screws
Heatsink
Ceramic Insulators
Upper Amp PCB
(channels 1 & 2)
Figure 4. E4 II Amplifier Module Assembly
6. Upper Power Amplifier PCB Removal
Note: The Upper Power Amp PCB contains
the circuitry for channels 1 and 2.
6.1 Perform procedure 5.
6.2 Disconnect the 34 pin ribbon cable that
connects to the upper amplifier PCB at PL8.
6.3 Disconnect the 4 wire power supply wire
that connects to the upper amplifier PCB at
PL12.
6.4 Using a flat blade screwdriver, pry the
top of the transistor clip out of the groove on
the heatsink assembly. Repeat for all four
transistors. Retain the clips for re-use.
6.5 Remove the two screws that secure the
PCB to the heatsink. These screws go
through the heatsink and into the board
mount clip.
6.6 Gently lift the PCB off of the two stand-
offs. You may have to squeeze the standoff
DISASSEMBLY PROCEDURES
Lower Amp PCB
(channels 3 & 4)
PCB Supports
with pliers in order to lift off the PCB. Try to
leave the ceramic insulators stuck to the
heatsink in their original positions if possible
as this will aid re-assembly.
7. Lower Power Amplifier Removal
Note: The Lower Power Amp PCB contains
the circuitry for channels 3 and 4 as well as
the power supply components for the unit.
7.1 Perform procedure 5.
7.2 Disconnect the harness going to the
larger PCB (26B) (channels 3 & 4).
7.3 Using a flat blade screwdriver, lift the top
of the transistor clip out of the groove of the
heatsink assembly. Repeat for all four
transistors. Retain the clips for re-use.
7.4 Remove the two screws that secure the
PCB to the heatsink. These screws go
through the heatsink and into the board
mount clip.
7.5 Gently lift the PCB off the two standoffs.
You may have to squeeze the standoff with
pliers in order to lift off the PCB. Retain the
ceramic insulators under the transistors for
re-use.
8. Power Transformer Removal
8.1 Perform procedure 5.
8.2 Disconnect the power transformer
harness from the power supply/power amp.
8.3 Remove the nut (5) and washer (6) that
secure the power transformer (7). There
should also be a cup washer and rubber pad
on top of the transformer.
Note: Older units will have a bolt and flat
washer.
8.4 Remove the two screws (15) that secure
the inlet assembly (9-13) to the rear panel.
Remove the ground nut (4). Lift out the
power transformer.
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