Unleveled Annunciator; Overmod Annunciator(9 - HP 8340B Manual

UNLEVELED ANNUNCIATOR (8)
NOTE: After performing the following procedure, use the
SHIFT M4 diagnostic test to help isolate
the cause of an
UNLEVELED
condition.
The UNLEVELED light indicates the status of RF output power.
If the UNLEVELED light
is
off,
the
output
power
is
leveled;
if the light
is on, the
power is unleveled.
1.
Press
[SHIFT] [PEAK].
This may solve the problem.
2.
Make
sure that the correct leveling
mode
Is
selected:
Internal leveling
=
I NT
External
leveling
=
XTAL
Power Meter Leveling
=
METER
If
you are using an external
millimeter-wave source module, you must
press [SHIFT] [XTAL], and
the
ENTRY display
should read:
EXT MODULE POWER: XX.XX dBm.
3.
Check that the power level
requested
is
not greater
than the maximum power specification at the
given frequency.
If
the instrument
is sweeping, make sure that the power requested does not
exceed
the
maximum power
specification for the entire band or bands that are swept.
4.
If
the output power is
unleveled at
all
power
levels and
all
frequencies, suspect an RF section
problem (A25 ALC detector or the A26 linear modulator).
5.
If
the power
levels at some frequencies and not others while the instrument sweeps, the
SYTM
may not
be tracking correctly. Try the
AUTO TRACKING
(press
[SHIFT] [PEAK]).
6.
If
the
power levels at
some
CW
frequencies and not at others, press
[PEAK]
to
optimize the SYTM
tracking at the frequency of interest.
7.
If
the power is
unleveled
in
low band (10
MHz
to
2.3 GHz)
only,
suspect a
low
band ALC or RF
section problem.
8.
If
the
power
is unleveled in
band
1
or above (2.3
GHz to
the maximum frequency), suspect
a
high
band ALC or RF section problem.
OVERMOD ANNUNCIATOR
(9)
You can cause
OVERMOD
if you use FM with
a
modulation rate that is
too high.
The other known causes of OVERMOD
are internal
instrument failures in the
AM,
pulse, or frequency
modulation circuitry (refer to A26 linear modulator information
in
the RF section).
To
determine
if
the instrument requires service:
1.
Disconnect any cables going to the AM or FM
inputs.
2.
Press
[INSTR
PRESET].
If
the
OVERMOD
annunciator comes back on, the instrument
requires
service.
HP 8340B/41B
Assembly-Level Service Overall Instrument Troubleshooting
A-41