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Model
8904A
Service
I
WARNING
I
Proper grounding
of
the instrument.
Any interruption of
the
protective
(grounding) conductor (inside
or
outside
the
instrument)
or
disconnection of
the protective earth terminal will create a potential shock hazard
that
could
result
in
personal injury. Grounding one conductor of a
two
conductor outlet
is
not sufficient. Whenever it
is
likely
that
the
protection
has
been impaired,
the instrument
must
be made inoperative
(that
is,
secured against unintended
operation).
If
this
instrument
is
to be energized via an autotransformer, make sure that
the autotransformer’s common terminal
is
connected to
the
earth terminal
of
the power source.
High voltages inside the instrument.
Areas with line voltages inside
the
instrument include
the
rear panel, power supply, and the line switch cable
harness. AC voltages
as
high
as
300
V
pp can be present
on
the
backlighting
drive to
the
LED
display.
(The
drive circuitry
is
on the front right
corner
of
the A2 Digital Assembly.)
Working around charged capacitors.
Capacitors inside the instrument
can still be charged even
if
the
instrument
is
disconnected from its source of
supply.
Replacing line fuses.
Make sure
that
only 250 volt
fuses
with
the
required
rated current and of
the
specified type (normal blow, time deb, etc.) are used
for replacement.
Do
not use repaired fuses
or
short-circuited fuseholders. To
do
so
could
create a
shock
or
fire hazard.
Disposing of the memory backup battery.
The
memory backup battery
on the
A2
Digital Assembly
is
a lithium battery. (A2
is
the large, horizontal
circuit board under the top cover near
the
front of the instrument.
The
battery
itself
is
near the front right corner of the board.)
The
following procedure
is
recommended
for
its disposal:
Discharge the battery by soldering a 50 kR resistor across both battery
terminals. Complete discharge will
occur
after one year, at 25°C.
Under Resource Conservation Recovery
Act
(RCRA) regulations,
the
com-
pletely discharged battery
is
considered “nonhazardous. However,
the
user
must be responsible for individual state and country regulations for battery
disposal.
8-2
Do
not unplug any boards
in
the Multifunction Synthesizer unless the
instrument
is
unplugged
or
switched to STB
Y
(standby). Some boards contain
devices which can be damaged
if
the board
is
removed when the power
is
on.
Use
conductive foam when removing MOS devices from sockets. Use care
when unplugging ICs from high-grip sockets.
rev.15DEC89