6-17
g. Remove the three mounting screws securing the
Timebase/Display board to the Center chassis and Power
Supply.
f. Disconnect P117 and P148 from J117 and J148.
J117 and J148 are located on the Timebase/Display board,
at the right-rear corner and center-rear edge, respectively.
e. Disconnect the ribbon cable connector at J121 of
the Timebase/Display board. J121 is located at the right-
rear corner of the board, under the ribbon cable discon-
nected in part d.
d. Disconnect the ribbon cable connector at J141 of
the Main board. J141 is located at the lower right-rear
corner of the instrument.
c. Disconnect the ribbon-cable connector from J100 01
the Timebase/Display board. J100 is located at the right-
front corner of the Timebase/Display board.
b. Set the instrument on a flat, smooth surface, with
its underside facing down and the Front panel facing
forward.
2. Timebase/Display Board Removal
a. Perform Step 1 to remove the cabinet.
The line-rectifier capacitors normally retain a charge
for several minutes after the instrument is powered
off and can remain charged for a longer period if a
bleeder resistor or other power supply problem
occurs. Before beginning any cleaning or work on
the internal circuitry of the instrument, discharge the
capacitors by connecting a shorting strap in series
with a
1
kil,
5
watt resistor across the capacitors.
Connect one end of the shorting strap/resistor com-
bination to upper-most terminal of S1020 (the termi-
nal connected through a wire to W310). Connect the
other end to pin
11
of T117 (the pin protruding from
the side of the transformer, near its right-rear
corner). Measure across those two connections with
a voltmeter to ensure the capacitors are discharged.
WARNING
I
Maintenance-2430 Service
Reverse parts a through h to install the cabinet.
h. Grasp the handle hubs (at right and left sides of the
instrument) and pull outward. While holding the hubs out-
ward, pull straight up from the rear of the cabinet to
remove the cabinet from the instrument.
Dangerous potentials exist at several points
throughout this instrument. If it is operated with the
cabinet removed, do not touch exposed connections
or components. Some transistors may have elevated
case voltages. Disconnect the ac power source from
the instrument and verify that the line-rectifier filter
capacitors have discharged before cleaning the
instrument or replacing parts (see label on the Low
Voltage Power Supply cover).
WARNING
I
g. Remove the four screws inside the four rear feet at
the instrument's back panel.
f. Set the instrument so it rests on the Front cover.
e. Install the protective Front cover over the Front
panel. Push on the cover to lock the cover's side tabs
around the Front panel's trim band.
d. Grasp the handle hubs (at right and left side of the
instrument) and pull outward. Rotate the hubs to position
the front of the handle away from the front of the
instrument.
c. Grasp the power cord plug (female end), rotate the
power cord retainer 1/4 turn, and pull it to remove the cord
from the Rear panel.
b. Disconnect the power cord from its receptacle at the
instrument's Rear panel.
1. Cabinet Removal
a. Disconnect the power cord from any ac power
source.
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