Maintenance-2445A/2455A Service
TROUBLESHOOTING
INTRODUCTION
Preventive maintenance performed
on
a regular basis
should
reveal
most potential problems before
an
instru-
ment malfunctions. However, should troubleshooting
be
required, the following information
is
provided to facilitate
location of a fault.
In
addition, the material presented
in
the "Theory of Operation"
and
"Diagrams" sections of this
manual
may
be
helpful while troubleshooting.
TROUBLESHOO"rlNG AIDS
Diagnostic Firmware
The
operating firmware
in
this instrument contains diag-
nostic routines that
aid
in
locating malfunctions.
When
instrument power
is
applied, power-up tests are performed
to verify proper operation of
much
of
the
instrument's cir-
cuitry. If a failure
is
detected, this information is passed
on
to
the
operator
in
the form of either a CRT readout or
illuminated
LED
indicators.
The
failure information directs
the operator to
the
failing block of circuitry. If the failure
is
such
that the processor
can
still execute
the
diagnostic
routines, the user
can
call
up specific tests to further
check the failing circuitry.
The
specific diagnostic routines
are explained later
in
this section.
Schematic Diagrams
Complete schematic diagrams are located
on
tabbed
foldout pages
in
the "Diagrams" section. Portions of cir-
cuitry mounted
on
each
circuit board are endosed
by
heavy black
lines.
The assembly number
and
name
of the
circuit are shown near either the top or the bottom
edge
of
the diagram.
Functional blocks
on
schematic diagrams
are
outlined
with a wide grey
line.
Components within the outlined area
perform the function designated
by
the block
label.
The
"Theory of Operation" uses these functional block
names
when
describing circuit operation
as
an
aid
in
cross-
referencing between the theory
and
the schematic
diagrams.
Component numbers
and
electrical values of com-
ponents
in
this instrument
are
shown
on
the schematic
diagrams. Refer to the first
page
of the "Diagrams·
sec-
tion for the reference designators
and
symbols
used
to
identify components. Important voltages
and
waveform
reference numbers (enclosed
in
hexagonal-shaped boxes)
are
also
shown
on
each
diagram. Waveform illustrations
are
located adjacent to their respective schematic diagram.
Circuit Board Illustrations
Circuit board illustrations showing the physical location
of
each
component
are
provided for
use
in
conjunction
with
each
schematic diagram.
Each
board illustration is
found
in
the "Diagrams" section
on
the back of a foldout
page,
preceding the first schematic diagram(s) to which it
relates.
The locations of waveform test points
are
marked
on
the circuit board illustrations with hexagonal outlined
numbers corresponding to the waveform numbers
on
both
the schematic diagram
and
the waveform illustrations.
Circuit Board Locations
The
placement
in
the instrument of
each
circuit board is
shown
in
a board locator illustration. This illustration
is
located
on
the foldout page along with the circuit board
illustration.
Power Distribution Diagrams
Power Distribution diagrams (diagrams
11
and
12)
are
provided
in
the "Diagrams· section to
aid
in
troubleshoot-
ing
power-supply problems.
Circuit Board Interconnection Diagram
A circuit board interconnection diagram (diagram
13)
and
tables listing the interconnecting
pins
and
signals car-
ried
are
provided
in
the "Diagrams· section following the
Power Distribution diagrams.
Grid Coordinate System
Each
schematic diagram
and
circuit board illustration
has a grid border along its left
and
top
edges.
A table
located adjacent to
each
diagram lists the grid coordinates
of
each
component shown
on
that diagram. To
aid
in
phy-
sically locating components
on
the circuit board, this table
also lists the grid coordinates of
each
component
on
the
circuit board illustration.
Near
each
circuit board illustration
is
an
alphanumeric
listing of
all
components mounted
on
that board. The
second column
in
each
listing identifies the schematic
diagram
on
which
each
component
can
be
found. These
component-locator tables are especially useful
when
more
than
one
schematic diagram
is
associated with a particular
circuit board.
6-5
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