Operating instructions

Maintenance---71387
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 .
To avoid component
damage, disconnect the
power source
before removing or replacing
semiconductors .
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 . 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 14- and 16-pin IC's
is with an IC test clip
. This device also serves as an
extraction tool .
The lead configuration for the
semiconductors
used in this instrument are
shown in
Figure 4-2,
and also on a pullout page in the
front
of
the
diagrams
section .
4- 8
Do not use an
ohmmeter scale that has a
high internal
current . High currents may
damage
the diode .
OBTAINING
REPLACEMENT
PARTS
All electrical and mechanical
part replacervrents can be
obtained through
your Tektronix Field
Office or
representative .
However, many of the standard electronic
components can be
obtained locally in less time
than is
required to
order them from
Tektronix, Inc . Before
purchasing
or ordering replacement
parts check the parts
list for
value, tolerance, rating,
and description .
Diodes .
A diode can be checked for an open or
shorted
condition
by measuring the resistance between
terminals
with an ohmmeter having a low
internal source current,
such as the R X 1 K scale . The
resistance shouldbe very
high in one direction and very
low when the meter leads
are reversed .
The cathode end of
each glass-encased diode is indicated
by a stripe, a
series of stripes, or a dot . The cathode and
anode ends of
a metal-encased diode are identified
by
the
diode symbol marked on the case .
For most silicon or
germanium diodes with a
series of stripes, the color code
identifies the four significant
digits of the JEDEC or
vendor number using
the resistor color-code system (e .g .,
a diode color-coded
yellow-brown-green-red indicates a
1N-4152 diode) .
Resistors . Check resistors
with an ohmmeter
.
See
the
Replaceable Electrical
Parts list for the tolerance
of the
resistors used in this
instrument . Resistors
normallydo
not need to be
replaced unless the measured
value varies
widely from
that specified .
Inductors .
Check for open inductors by
checking
continuity with
an ohmmeter . Shorted or
partially shorted
inductors can
usually be found by
checking the waveform
response
when high-frequency
signals are passed
through
the circuit . Partial
shorting often reduces high-
frequency
response .
Capacitors . A leaky or
shorted capacitor can usually
be
detected by checking
resistance with an ohmmeter on
the highest scale .
Do not exceed the voltage
rating
of
the
capacitor .
The resistance reading should
be high after
initial charge
of the capacitor . An open
capacitor can best
be detected
with a capacitance meter or
bychecking that
the
capacitor passes ac
signals .
8 .
REPAIR AND ADJUSTMENT
. If any defective parts
are located, follow the
replacement procedures
given in
Corrective Maintenance .
Be sure to check the
performance of any
circuit that has been repaired or had
any electrical components
replaced .
MAI NT
NAN
Corrective maintenance
consists of component
replacement and instrument repair .
Special techniques required to
replace components
in this instrument are
given here .
When
selecting replacement parts,
remember
that the
physical size and shape of
a
component
may affect the performance of
the
instrument, particularly at
high frequenies .
All parts should be direct
replacements
unless a different
component will not
adversely affect
instrument performance .
NOTE