1.
Using a 1 /16-inch Allen wrench, loosen the set
screws
in
the
CH
1 VOLTS/DIV
VAR,
CH
2 VOLTS/DIV
VAR,
and
A
and
B SEC/DIV VAR knobs
and
remove these
three knobs from their control shafts.
2.
Using a 1/16-inch
Allen
wrench, loosen the six set
screws
in
the
CH
1 and
CH
2 VOL TS/DIV knobs,
and
the
SEC/DIV knob. Remove these three knobs from their con-
trol shafts.
3.
Using firm outward pressure,
pull
off the remaining
knobs. Note the locations of the knobs with indicator bars
for reference during reinstallation.
4.
On
the rear of the assembly, remove the four screws
securing the black variable resistor holder assembly.
5.
Separate
and
slide out the above assembly with
attached variable-control shafts. Avoid stressing the shafts
to the side while sliding the assembly out.
FRONT-PANEL REMOVAL.
Use
the following
procedure to further disassemble the Front-Panel circuit
board assembly.
1.
Separate the Front-Panel
and
variable resistor holder
assembly as described above (if not already done).
2.
Lift up the circuit board carefully
to
avoid dislodging
any of the square push buttons from their switches.
3.
Lift off the black plastic switch guide and mounting
ring.
To reassemble
and
reinstall the Front-Panel assembly,
perform the reverse
of
the preceding instructions.
When
reinstalling the circuit board, align
all
push buttons and
LEDs with the black plastic switch guides before installing
and
tightening the screws.
A 10 and A
11-Channel
1 and Channel 2
Attenuator Assembly Removal
Removal of either the Channel 1 or Channel 2 Attenua-
tor assembly
is
accomplished by the following steps:
Maintenance-2445A/2455A Service
1.
Remove
the instrument Cabinet
as
described
in
that
procedure.
2.
Remove
the Front-Panel assembly
as
described
in
that procedure.
3.
Remove
the two screws holding the Attenuator sup-
port bar
and
remove the bar.
4.
For
each
attenuator, remove the two screws holding
the Attenuator to the front subpanel
and
the two screws
holding it to the
Main
board (through access holes
in
the
front
panel
compartment of the chassis).
5.
Disconnect the associated multipin connector (either
P10
for Channel 1 or
P11
for Channel
2)
from the Main
board.
6.
Remove
the two screws holding the preamplifier
shield
and
ground clip and remove them.
7.
Desolder the two Attenuator output leads
and
the
compensation capacitor lead.
8.
Unplug the Attenuator
by
gently pulling the assembly
straight
up
and away from the Main Board.
To reinstall a removed Attenuator assembly, perform
the reverse of the preceding steps.
A
1-Main
Board Removal
Removal of the Main Board
is
accomplished
by
the fol-
lowing steps:
1.
Remove
the instrument Cabinet
as
described
in
that
procedure.
2.
Remove
the Vertical Bracket
as
described
in
that
procedure.
3.
Remove the Front-Panel circuit board assembly
as
described
in
that procedure.
6-29
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