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Wavetek 3000 - CW;AM Mode Selection; RF Level Programming; Option 1 B Maintenance

Wavetek 3000
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volts
.
As
the
output
swings
down
toward
0,
Q213
turns
on
and
supplies
current
to
the
front-panel
UNLEVELED
lamp
;
then,
.as
the
outputrises
toward
+7
volts,
Q213
again
turns
off and
preventscurrent
flow
to
the
UNLEVELED
lamp
.
This
on/off
cycle
of
Q213
thus
causes
the
UNLEVELED
lamp
to
flash
.
After
the
external
RF
signal
is
removed,
IC201
can be unlatchedby
momentarilyremovingAC
power
from
the
instrument
.
CW/At1
ModeSelection
With
the
instrument's
140DULATION
MODE
switch
set
to
its
AM
position,
mode
select
relay
K201
enables
remote
selection
of
either
CW
or
AM modes
.
Q212
is
an
inverter
which
controls
relay
driver
Q211
.
With
the
base
of
Q212
(J101
pin
30)
grounded,
Q212
is
turned
off
;
therefore,
Q211
is
turned
on
and
effectively
grounds
one
side
of
K201
's
coil
.
This
energizes
K201
and
opens
its
contacts
to
place
the
instrument
in
its
CW
mode
.
With
relay
K201
in
its
de-energized
(normally
closed)
position,
modulation
signals
(DC,
400
Hz, 1
kHz, or
EXT
.)
from
the
Modulation
Board
are
applied
through
the
relay
contacts
to
the
Meter
Board
where
they
are
combined
with
level
programmingvoltage
to
produce
amplitude
modulation
of
the
Output
Amplifier
output
.
When
K201
is
energized,
its
contacts open
;
thus,
modulation
signals
are
removed
from
the
Meter
Board
and
instrument
is in
`he
CW
mode
.
RF
LevelProgramming
The
ProgrammableAttenuator
contains
one
10 dB
section and
four
20
dB
sections
;
however,
two
of
the
2Q
dB
sections
are
wired
together
to
provide
40
dB
of
attenuation
.
The
resulting
four
attenuator
pads
(10
dB,
20
dB,
40
dB,
and
20
dB)
can
be
combined
in 10 dB
steps
to
give
attenuationranging from
0
to
90
dB
.
The
positive
terminal
of
eachattenuator
section
is
connected
to
+27
volts
DC
;
then,
each
attenuator
pad
is
activated
when
required
by
grounding
its
negative
terminalthrough
one
of
four
identical
inverter/divider
transistor
circuits
.'
For
example,
to
insert
10 dB of
attenuation,
the "1"
wire
(J101
pin
26)
is
grounded
by a
contactclosure
or
TTL
signal
.
This
turns
off
inverter
Q210
which then
turns
on
driver
Q209
and
grounds
the
negative
terminal
of
the
10
dB pad through
R229
.
If
the "8"
wire
(J101
pin
29)
is
grounded,
80
dB of
attenuation
will
be
activated
as
follows
.
The
base
of
Q204
is
grounded
directly
.
The
base
of
Q206
is
grounded
through
CR205,
and
the
base
of
Q208
is
groundedthrough
CR206
.
This
turns
off
inverters
Q204,
Q206,
and
Q208
which
turns
on
drivers
Q203,
Q205,
and
Q207,
respectively
.
The
drivers
ground
the
negative
terminals
of
the
20
dB,
40
dB,
and
20
dB
attenuator
pads
through
R226,
8227,
and
R228,
respectively
.
Note
that
CR205
and
CR206
are
forward-biased
and
conduct
only
when
the
"8"
wire
is
grounded
.
If
the
"4"
wire
or
"2"
wire
is
grounded,
the
diodes
are
reverse-biased
and
do
not
conduct
.
MAINTENANCE
If
a
malfunction
occurs,
the
trouble
can
be
localizedand
repaired
with
the
aid
of
the circuit description
and
schematic
.
No
preventative
maintenance
is
required
for the
RF
LevelProgrammingoption
;
however,
periodic
testing
is
recommended
to
insure
proper
operation
of
the
programmingand
the
Protection
Circuits
.
The
level
programming
can
be
checked
with
the
followingprocedure
:
NOTE
OPTION
1B

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