Operating
Instructions—7A42
TABLE
2-1
(CONT)
7A42 Self-Test Failure Messages
TRIGGER
FUNCTION
(LED
display)
SWITCHING THRESHOLD
VOLTS
and crt readout display
Severity
of failure;
functional
usability
of instrument
Indication
Test
Indication
Test
CH2,
second
column
(cont)
Trigger
(cont)
23
Boolean
logic.
Some
trigger
functions
may
not
be
operational.
Repair
before
use.
26
A THEN
B
Avoid
use
of
A
THEN
B
mode.
Repair when
convenient.
CH3,
second
column.
Edge
detectors
34
Edge
detectors.
Avoid
use
of
Edge-qualified
triggering
mode
and
external
clock.
Repair
when
convenient.
CH4,
second
column.
EXT
CLOCK
70
EXT
CLOCK
Avoid
use
of
external
clock.
Repair when
convenient.
FRONT-PANEL
INITIALIZATION
While
getting
acquainted
with
the
7A42,
it
might
be
desirable
to
begin operation
with
the front-panel
controls
set
to a known state
(initialized).
The
front
panel
will
initialize
to the
control
settings
listed
in
Table
2-2
and
as
shown in Figure 2-12. To
initialize
the
7A42
front-panel
control
settings,
see
Exercise
1
in
the
Get-
Acquainted Exercises
of
this
section.
BATTERY BACKUP
Upon
completion
of
the
self-test
sequence,
the
7A42
battery
backup
feature
restores
the
7A42
front-panel
control
settings
to
the
same
settings
that
were
present
when
the
power
was
turned
off.
2-52
