Tektronix 7B10 Instruction Manual page 39

Maintenance---7B1
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2.
CHECK ASSOCIATED EQUIPMENT
Before
troubleshooting,
check
that the
equipment used
with
this
instrument
is
operating
correctly
Check
that
the
signal
is
properly connected and
that
the
interconnecting cables are not
defective. Also,
check
the
power
source.
If
the trouble
persists,
the time-base
unit
is
probably
at fault.
3.
VISUAL
CHECK
Visually
check
the portion
of
the instrument
in
which
the
trouble
is
located.
Many
troubles
can be
located
by
visible
indications
such
as
unsoldered
connections, broken
wires,
damaged
circuit
boards,
damaged
components.
4.
CHECK INSTRUMENT ADJUSTMENT
Check
the
adjustment
of this
instrument,
or
the affected
circuit
if
the trouble appears
in
one
circuit
The
apparent
trouble
may
be
the result
of
misadjustment. Complete
adjustment
instructions are provided
in
Adjustment and
Performance
Check, section
5.
5.
ISOLATE
TROUBLE TO A
CIRCUIT
To
isolate trouble
to a circuit,
note the
trouble
symptom.
The sympton
often
identifies
the
circuit
m
which
the
trouble
is
located.
When
trouble
symptoms
appear
in
more
than
one
circuit,
check the
affected
circuits
by
taking
voltage
and waveform
readings. Incorrect
operation of
all
circuits
often indicates trouble
in
the
power
supply.
Check
first
for correct voltages of the
individual supplies.
However,
a
defective
component
elsewhere
in
the instrument can appear as
a
power-
supply trouble
and
may
also affect the operation
of
other
circuits.
The
Troubleshooting Chart
at
the rear
of
the
manual
serves as
a
guide
for locating a defective
circuit.
Start
at
the top
of
the chart
and perform
the
checks
given
on
the
left
side
of
the page
until a step
is
found
that
does
not
produce
the indicated
results.
Further checks,
or
the
circuit
in
which
the trouble
is
probably
located,
are
listed
to
the
right of
the step
The shaded
blocks
on
the
Troubleshooting Chart
indicate
circuit(s)
that
may
cause
instrument
malfunction.
The
circuit(s) listed
in
shaded
blocks are discussed
in
detail
in
the Theory
of
Operation
section
of this
manual.
This chart
does
not
include
checks
for
all
possible defects;
use
steps 6
and
7
in
such
cases.
After the defective
circuit
has been
located,
proceed with
steps 6
and
7
to
locate the defective component(s).
6.
CHECK VOLTAGES
AND WAVEFORMS
Often
the defective
component
can
be located by
checking
for
the correct voltages
and waveforms
in
the
circuit.
Refer
to
the
diagrams
section
at
the
rear of the
manual
for typical
voltages
and waveforms.
NOTE
Voltages
and waveforms
on
the
diagrams
are
not absolute
and
may
vary
slightly
between
instruments.
To obtain operating conditions
similar
to
those
used
to
take these
readings,
see the voltage
and waveforms
page
adjacent
to
each schematic
diagram.
Note
the
recommended
test
equipment,
front-panel
control
settings,
voltage
and waveform
conditions,
and
test
equipment
cable
connection
instructions.
7.
CHECK
INDIVIDUAL
COMPONENTS
The
following
procedures
describe
methods
for
checking
individual
components. Two-lead components
that
are
soldered
in
place are best
checked
by
first
disconnecting
one end
This
isolates
the
measurement from
the
effects
of
surrounding
circuitry.
WARNING
To avoid
electric
shock,
always
disconnect the
instrument from
the
power
source before
replacing
components.
Transistors
The
best
check
of
transistor operation
is
actual
performance under
operating
conditions.
A
transistor
can
be
most
effectively
checked
by
substituting a
new
component
or
one
that
has been checked
previously.
However, be sure
that circuit conditions are not
such
that
a
replacement
transistor
might
also
be damaged.
If
substitute transistors are not
available,
use
a
dynamic
tester
Static-type testers are not
recommended,
since
they do
not
check operation under simulated
operating
conditions.
Integrated Circuits
Integrated
circuits (IC's)
can be checked with
a voltmeter,
test oscilloscope, or
by
direct substitution.
A
good
understanding
of circuit
operation
is
desirable
when
troubleshooting
circuits
using
IC's.
Use
care
when
checking voltages
and waveforms around
the
IC's
so
that
adjacent leads are
not
shorted together
A
convenient
means
of
clipping
a test
probe
to
the
in-line IC's
is
with
an
1C test
clip.
This device also serves as an
extraction
tool
The
lead configuration
for
the semiconductors used
in this
instrument
are
shown
on
a pullout
page
in
the
front
of
the
diagrams
section.
^
CAUTION
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(.
^
^
X"
^
When
checking
diodes,
do not use an
ohmmeter
scale
that
has
a
high
internal
current,
since high
currents
may damage
the
diodes
under
test.
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