THEORY
OF
OPERATION
Test 5.
Each
memory location of the
Non-Volatile RAM
is
checked with a
checksum.
Test 6. The
low-pass
filters on the Output
assembly
are tested by setting
the
frequency
at
the top of each of the four
half^octave
non-HET bands and
verifying that
the output is leveled. Then, the
frequency
is set above the
cutoff
frequency, and
the
output is checked to see
if
the output is
unleveled.
Test 7.
The
synthesizer
operation is verified by
programming
the Generator to a
normal operating
frequency and checking to see
that
the instrument is
locked. The
Generator is then programmed to a
synthesizer frequency
below 225 MHz
and
then above 550 MHz and is
checked to see that the
instrument becomes
unlocked. Finally, all frequency
reference circuitry is
turned
off and checked to see
that
the Generator becomes
unlocked.
Test
8. The Generator PLL
operation is verified by
forcing a large
change
in
frequency.
When this is done,
the Generator should
become unlocked
and then lock again.
Test 9,
Frequency
modulation is
verified by overmodulating the
carrier and then
checking
the unlocked indicator.
This
is done by programming
internal
FM on and
programming the KV DAC to a
higher than normal
value.
Test
10. Amplitude
modulation is verified by
overmodulating the carrier
and
then
checking the
unleveled indicator. This is done by
programming a high
output level and programming
INT AM on with a high
AM
depth.
3-26.
Service Special
Functions
There
are two special
function
self tests for the front panel
indicators and keys.
These
special
function
self tests are
described
in the following:
1.
The front panel
displays
are checked any time by
pressing the [SPCL]
[0][3]
keys.
When this is
done
the microprocessor lights all
display
segments. This
test
is
terminated by
pressing
any key on the instrument.
2.
Check the
normally
open front panel keys by
pressing
the [SPCL]
[0][4]
keys.
Now, each key
pressed
has its row and column
address
displayed in the
center of
the FREQUENCY
display field. The special
function is
exited by pressing
the
[CLR/LCL]
key.
3-27.
Status Signals
Five status signals
indicate the Generator
option complement, and
these status bits
are
interrogated
at power-on self
test
as follows:
HSOPTL
=
0
indicates Option
-130 High-Stability
Reference
is installed.
MSREFL
=
0 indicates
Option
-132
Medium-Stability
Reference is
installed.
lEINL
=
0
indicates Option
-488 IEEE-488 Interface is
installed.
LRFML
=
0 indicates
the Option
-651
Low-Rate
FM is installed.
3-7
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