Fault Annunciator (7 - HP 8340B Manual

FAULT ANNUNCIATOR (7)
NOTE: After performing the following procedure, use the
SHIFT M4
diagnostic test to help isolate
the cause of an
FAULT
condition.
The FAULT light monitors the status of the
five internal functions described below.
1.
If
the
FAULT
light
is
on, press
[SHIFT] [MANUAL].
FAULT: CAL KICK ADC PEAK TRK appears
in
the
ENTRY DISPLAY.
The name of
the faulty function
is
flashing.
CAL
Refers to the calibration
constants stored in
memory. The calibration constants are
checked only at instrument preset.
If CAL
is
flashing, the instrument has
resorted to
default calibration constant data. The major effect of this condition
is
that RF power
output flatness and accuracy are degraded.
To remedy this situation, you must re-enter the the factory-determined calibration
con¬
stants (see
HOW TO RESTORE FACTORY-OPTIMIZED CALIBRATION CONSTANTS).
KICK
Refers to the kick pulses used
to
reset the YO (YIG oscillator) and
SYTM (switched
YIG-
tuned multiplier). This fault is can be caused by
a
kick pulse that is
too wide. suspect
a
problem
with the kick pulse caused by the A54 YO pretune,
ASS YIG oscillator driver (in
the sweep generator-YO loop functional group), or the A28
SYTM
driver assemblies
(in
the
RF
section functional
group).
ADC
Refers to
a
check performed
on the
ADC (analog-to-digital converter) circuits on the
A27
level control
assembly. This check is
done at instrument preset or at
power
on.
ADC
indicates that the
POWER
dBm display may
indicate
a
different
power
than the
instrument
is actually producing.
Also, an
ADC
failure does not allow the
PEAK and
auto tracking
(SHIFT PEAK)
functions to operate properly.
If
this
annunciator
is
on,
suspect
a
problem on the A27 level control assembly (see
the
RF section functional
group).
PEAK This refers to an instrument function that peaks the RF output
power
at
a
CW
fre¬
quency by fine tuning
the
SYTM (which
is tuned
to the
YO frequency). This fault
can
only
come on
if
you
press [PEAK].
If PEAK
is
flashing,
something
is
wrong with the circuitry that
peaks the
SYTM. PEAK
indicates
that the instrument is
not able to optimize
its
output power. While
this instru¬
ment failure requires service to correct, the optimum
power
may not be
adversely
affected. Suspect
the
A28 SYTM
driver or
A27
level
control assembly.
TRK
Refers to
an
instrument function that peaks the RF output power while the instrument
is
sweeping. This
fault can only occur
if
you press
[SHIFT]
[PEAK].
The TRK light Indicates the same things as
a
flashing PEAK.
The FAULT LED (located on the A2 display driver assembly)
is
driven by
the
A3 display processor,
annunciator latch/driver
circuit.
The instrument microprocessor
detects an error from the circuitry,
outputs the appropriate
bits
to turn the LED
on, and outputs
address
15:RO to latch
the data
bits.
A-40
Assembly-Level Service
Overall Instrument
Troubleshooting
HP 8340B/41B