use
diagnostic
aids
inherent
in
the instrument's operating
firmware
and
will
locate
many
circuit faults. The next four
procedures are check steps that ensure proper control
settings, connections, operation,
and
adjustment. If the
trouble
is
not located
by
these checks, the remaining steps
will
aid
in
locating the defective component.
When
the
defective component
is
located, replace it using the
appropriate replacement procedure
given
under "Correc-
tive Maintenance·
in
this section.
~
Before using any test equipment to make measure-
ments on static-sensitive, current-sensitive,
or
voltage-sensitive components
or
assemblies, ensure
that any voltage
or
cuffent supplied
by
the test
equipment does
not
exceed the limits
of
the com-
ponent to
be tested.
1. Power-up Tests
The
instrument performs automatic verification of
much
of
the
instrument's circuitry
when
power
is
first applied.
The
Kernel
tests verify proper operation of the Micropro-
cessor, the
ROM,
and
the RAM. If
all
Kernel
tests pass, a
second
level
of checks, the Confidence tests, are per-
formed. The Confidence tests,
when
passed,
give
the user
a
high
degree of assurance that the instrument
is
functioning properly.
If a
Kernel
test or Confidence test fails,
the
area of
failure
is
identified either
by
a message
on
the
CRT
{if the
instrument
is
able
to produce a display) or
by
an
error
code displayed
on
the front-panel
LED
indicators. If a
failure occurs, refer to the "Diagnostic Routines· discus-
sion later
in
this section for definitions of error messages
and
LED
error codes.
Once
a problem area
has
been
identified, the associ-
ated troubleshooting procedure should
be
performed to
further isolate the problem. The troubleshooting pro-
cedures are located
on
tabbed-foldout
pages
in
the.
"Diagrams· section at the rear of this
manual.
2. Diagnostic Test and Exerciser Routines
Each
of the tests automatically performed at power-up,
along with several other circuit exercising routines,
may
be
individually selected
by
the user to further clarify the
nature of a suspected failure.
The
desired test or exerciser
is
selected
by
scrolling through a
menu
of the available
routines
when
under control of the Diagnostic Monitor.
Entry into the Diagnostic Monitor
and
its
uses
are
explained
in
the • Diagnostic Routines· discussion later
in
this section.
Maintenance-2445A/2455A Service
3. Check Control Settings
Incorrect control settings
can
give a false indication of
instrument malfunction. If there
is
any
question about the
correct function or operation of
any
control, refer to the
Operators Manual.
4. Check Associated Equipment
Before proceeding, ensure that
any
equipment
used
with
the
instrument
is
operating correctly. Verify that input
signals are properly connected
and
that the interconnect-
ing
cables are not defective. Check that the ac-power-
source voltage to
all
equipment
is
correct.
5. Visual Check
Perform a
visual
inspection. This check
may
reveal
bro-
ken
connections or wires, damaged components, semicon-
ductors not firmly mounted, damaged circuit boards, or
other
clues
to the
cause
of
an
instrument malfunction.
6. Check Instrument Performance and Adjustment.
Check the performance of either those circuits where
trouble appears to exist or the entire instrument. The
apparent trouble
may
be
the result of misadjustment.
Complete performance check
and
adjustment instructions
are
given
in
Sections 4
and
5 of this manual.
7. Isolate Trouble to a Circuit
To isolate problems to a particular
area,
use
any
symp-
toms noticed to help locate the trouble. Refer to the
trouble-shooting charts
in
the "Diagrams· section
as
an
aid
in
locating a faulty circuit.
When
trouble symptoms appear
in
more than
one
cir-
cuit, first check
the
power supplies, then
check
the
affected circuits
by
taking voltage
and
waveform readings.
Check first for the correct output voltage of
each
individual
supply. These voltages are measured between the power
supply test points
and
ground.
{See
schematic diagrams
8,
9,
10,
and
associated circuit board illustrations
in
the
"Diagrams· section.) If the power-supply voltages
and
rip-
ple
are within
the
listed ranges,
the
supply
can
be
assumed to
be
working correctly. If they are outside the
range,
the supply
may
be
either misadjusted or operating
incorrectly.
The
Low Voltage Power Supply levels
are
interdepen-
dent.
All
the low voltage supplies
use
the + 1 0 V reference
for their reference
levels.
If more than
one
of the low volt-
age
supplies appears defective, repair them
in
the
following order:
+10
V
REF,
+5
V Digital,
+87
V,
+42
V,
+15
V,
+5
V Analog,
-15
V,
-8
V,
and
-5
V.
6-7
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