NOTE
TROUBLE SHOOTING
Considerable
force
may
be
nec
essary
to
push
the
mounting
rods
into
the
nylon
collars.
Be
sure
that
you
apply
this
force
to
that
area
of
the
ceramic
strip
directly
above
the
mounting
rods.
Removing
the
Cabinet
Each
side
panel
and
the
bottom
panel
are
individually
removable
when
service
becomes
necessary. To
remove
a
side
panel
release
the
fasteners
near
the
front
and back
and
swing
the
top
of the
panel
out
until
the
bottom
hinge
releases.
To
remove
the
bottom panel
release the
four
fasteners
and
lift
the
panel
off.
To replace
the
panels,
reverse
the
process
above.
Each
fastener is
designed so
that the
first
one-quarter
turn
engages
an
ear
on
the
fastener
with
the
oscilloscope
frame.
Further
turning
of
the
screw
locks
the
ear
in place.
WARNING
Be
careful
of high
voltages.
The
lower
voltage
buses are
potentially
more dangerous
than
the
crt
accel
erating
voltages because of
the
higher
current
capabilities and
larger
filter
capacitors
in
these
supplies.
When
you
reach
into
the
instrument
while
it
is turned
on,
do
not
hold
the
frame
with
the
other hand.
If
possible,
stand
on
an insulated
floor and
use
insulated
tools.
234-Volt
Operation
Unless
tagged
otherwise,
this
oscilloscope
is
connected
at
the
factory
for
117
- volt operation.
To
connect
if
for
234
-volt
operation,
remove
the
jumper
between
terminals 1
and
2 and the
jumper
between
terminals
3
and
4
on
the
power
transformer.
Connect
a
jumper
between
ter
minals
2
and
3.
Move
the
black
fan lead,
which
is connected
to
the
lead
coded
brown
-
brown-brown
at
the
ceramic
strip
behind
the
power
transformer,
to
the
next lead
which
is
coded
brown-red-brown.
Install
the
proper
size
fuse.
General
This
is a
complex
electronic
instrument.
There
is
no
simple way of
locating
troubles.
With
an
understanding
of
the
circuits,
you
will
generally
be
able
to
localize
the
trouble
just
from
front
panel
observations.
Troubles
are
usually
caused
by
tube
failure.
You
can
frequently
correct
them
by
finding
the bad
tube
and
replacing
it
with
a
good
one.
However, sometimes
a
tube
burns
up
resistors
or
overstresses capacitors
when
it
fails,
and
in these
cases
you
will
also have to
find these
bad
components.
Sometimes
you
can
find
them
by
visual inspection.
One
way
to
find
bad
tubes
is
to
try
replacing
suspected
tubes
with
good
ones.
If possible,
replace
all
suspected
tubes
at
one
time,
and
if
the trouble
is
helped,
return
the
old
ones,
one
at
a
time,
until
the
offending
one
is discovered.
Power
Supply
Correct
operation
of the
power
supply
is
necessary
for
proper operation
of
most
other
circuits
in
the
instrument.
So
an
early
step
to
take
when
you
look
for
troubles
is
to
check
the
voltages of
the
power
supplies.
All
the
regulated
supplies
should
be
within five
per
cent
of
their
rated values
and
should
remain
steady
as
the
line
voltage is
varied
from
105
to
125 volts
or
210 to
250
volts.
If
the
instrument
fails
to
operate
at
all,
including
the
fan
and
pilot
light,
check
the
source
of
power
and
determine
that
the
power
cord
plug
is
securely
in
place.
Then
check
the fuse
at
the
back
of
the
instrument
near
the
power
receptacle.
If
the
instrument
has
been
operating
but
has
just
stopped,
it may have
overheated and tripped
the
thermal
cutout.
The
thermal
cutout
will
reset
itself
when
the
instrument
cools
down
enough.
Possible
causes of
overheating
are
fan
stoppage, restriction of
air
circulation
or
high
room
temperature.
Be
sure
the
air
filter
is
clean.
Deflection
System
The
cathode-ray-tube
display
should
help
in
locating
the
source
of
trouble.
If
no
spot
Maintenance
-
Type
515/515A
4-5
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