Tektronix TM 504 User Manual

System
Maintenance—
TM
504
known
to
be operating
properly. If the
trouble
persists after
substitution,
then the
power
module is probably
at fault.
Moving
a properly operating plug-in
from
compartment
to
compartment will help
determine if
one
or more compart-
ments has
a
problem.
Visual
Check
Inspect the
portion of the
system in which
the
trouble is
suspected.
Many
troubles
can be
located
by visual clues
such
as unsoldered
connections,
broken wires,
damaged
circuit
boards,
damaged components,
etc.
Instrument
Calibration
Check
the
calibration
of the
suspected
plug-in
module
or
the
affected
circuit if
the
trouble Is
obviously
in
a
certain
circuit. The
trouble
may
only
be
a
result
of misadjustment
or may
be corrected by
re-calibration.
Complete
calibration
instructions
are
given
in
the manual for
each
instrument in
the
system.
Circuit Isolation
Note the
symptom.
It
often
identifies the
circuit In
which
the trouble is
located. When trouble
symptoms
appear in
more than
one
circuit,
check the
affected circuits
by making waveform
and voltage
measurements.
Incorrect
operating of all
circuits often means
trouble in
the
power supplies.
Using a multimeter, check first
for
correct voltages
of the individual
regulated
supplies
ac-
cording
to
the plug-in
module schematics
and calibration
procedures.
Then check
the
unregulated
supplies
of the
power
modules. Defective
components
elsewhere in
the
instruments
can
appear
as power supply
problems. In
these
instances,
suspected circuits
should
be disconnected
from
apparently
bad power supplies
one
at
a
time
to narrow the
search.
Voltages
and Waveforms
Often
defective
components can
be located
by
using
waveform
and voltage indications
when they
appear on the
schematic
or
in
the calibration
procedures.
Such waveforms
and voltage
labels
are typical
indications
and will
vary
between instruments.
To
obtain
operating
conditions
similar
to those
used to
take these readings,
refer
to
the
first
diagram in the service
sections.
Component
Checking
If
a
component
cannot
be disconnected
from
its
circuit,
then
the
effects
of the
associated circuitry
must
be
considered
when
evaluating
the
measurement.
Except
for
soldered in
transistors
and integrated
circuits,
most
com-
ponents
can be lifted
at
one
end from the
circuit
board.
Transistors
and IC's.
Turn the
power switch off
before
removing
or replacing
any
semiconductor.
A good check of
transistor
operation is
actual perform-
ance
under
operating
conditions.
A transistor
can
most
effectively
be checked by
substituting
a new component
for
it
(or
one
which
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.
A suction-type
de-
soldering
tool must
be used
to remove
soldered-in
tran-
sistors;
see
component
replacement
procedure for
details.
Integrated
circuits can
be checked
with
a voltmeter,
test
oscilloscope,
or
by direct
substitution.
A
good
under-
standing of the circuit
description is
essential
to trouble-
shooting circuits
using
IC's. Operating
waveforms, logic
levels,
and other operating
information
for the
IC's are
given in
the circuit
description
information
of the
appro-
priate
manual.
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-pln
in-line
IC's
is
with an
Integrated
circuit
test
clip.
This device
also doubles
as
an
extraction
tool.
Diodes.
Do
not use
an ohmmeter
that has
a
high internal
current.
High currents
may damage
the
diode.
A diode
may
be checked
for an open
or shorted
condition
by measuring the
resistance
between
terminals.
With
an ohmmeter
scale having
an internal
source of
between
800 mV and
3 V,
the
resistance
should
be
very
high in
one
direction
and
very
low
when the
leads
are
reversed.
Resistors.
Check the
resistors with
an
ohmmeter.
Resistor
tolerances
are
given
in
the Electrical
Parts
List.
Resistors
do
not normally
need
to be replaced unless
the
measured value varies
widely
from the specified
value.
Capacitors.
A leaky
or shorted
capacitor can be
detected
by checking
resistance
with
an ohmmeter
on
the highest
scale.
Use an ohmmeter
which will
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
capacity
meter,
or by checking
whether
it
passes ac signals.

Tektronix TM 504 Specifications

General

Brand	Tektronix
Model	TM 504
Category	Control Unit
Language	English