F
ault
Indicators
The
HP
70001A
has
three
fault
indicators
.
While
these
indicators
are
located
in
the
mainframe
,
problems
external
to
the
mainframe
can
cause
the
indicators
to
turn
on.
External
problems
should
be
investigated
before
troubleshooting
the
mainframe
.
V
OL
T/TEMP
If
this
fault
indicator
is
on
steady
,
check
for
the
following
problems
before
deciding
the
mainframe
needs
repair
.
T
emperature
limits
Excessive
ambient
temperature
,
exceeding
55
C
will
cause
the
V
OL
T/TEMP
fault
indicator
to
come
on
and
stay
on.
Move
the
mainframe
to
a
cooler
environment
and
wait
for
the
temperature
to
decrease
to
the
normal
operation
range
.
1
When
the
temperature
decreases
the
mainframe
will
restart
itself.
If
the
indicator
goes
out
after
the
mainframe
has
cooled
the
mainframe
is
probably
not
at
fault.
If
the
problem
persists;
when
the
mainframe
attempts
to
restart
itself,
verify
that
both
cooling
fans
are
operating
by
checking
the
airow
into
both
of
the
rear-panel
fan-intake
openings
of
the
mainframe
.
Low
input
voltage
If
the
line
voltage
is
low
or
the
voltage
selector
setting
does
not
agree
with
the
input
voltage
,
the
V
OL
T/TEMP
fault
indicator
will
come
on.
Check
the
ac
input
voltage
and
set
the
voltage
selector
switch
as
follows
.
115
V
position
for
90|132
V
ac
line
input
voltage
.
230
V
position
for
198|264
V
ac
line
input
voltage
.
If
the
low
voltage
condition
is
corrected,
the
unit
will
restart
itself.
Note
V
ery
long
ac
wiring
runs
may
cause
the
ac
power
voltage
at
the
mainframe
to
drop
below
an
acceptable
limit,
when
the
mainframe
applies
its
load
to
the
ac
line
.
This
will
cause
the
mainframe
to
cycle
on
and
o.
No
damage
will
occur
as
a
result.
The
cure
is
to
correct
the
power
wiring
or
voltage
.
A
ashing
V
OL
T/TEMP
fault
indicator
can
be
caused
by
an
impedance
mismatch
between
the
ac
line
and
the
mainframe
input.
This
usually
occurs
only
at
extremely
low
temperatures
(below
0
C).
The
cold
input
thermistors
(now
a
high
impedance)
reduce
the
line
voltage
.
An
under
voltage
condition
is
sensed
and
the
mainframe
shuts
o.
The
reduced
load
allows
the
sensed
line
voltage
to
rise
and
the
unit
turns
back
on.
1
Keep
in
mind
that
the
internal
temperature
of
the
instrument
will
change
with
a
corresponding
change
in
the
ambient
room
temperature
,
and
that
there
is
a
delay
between
a
change
in
ambient
temperature
and
a
change
in
internal
temperature
.
It
can
take
20
minutes
or
more
for
an
overheated
mainframe
to
cool
internally
to
an
acceptable
temperature
,
since
no
cooling
air
is
being
moved
by
the
fans
when
the
supply
is
shut
down.
5-2
T
roubleshooting
