HP 8753D Option 011 User Manual

indicated. The
troublesho oting
pro cedures
later in
this c
hapter
detail
the
steps
to
trace
the
cause
of
the
problem.
Shutdown
Circuit
The
shutdo
wn
circuit
is
triggered
b
y
o
v
ercurren
t,
o
verv
oltage, underv
oltage, or
o
v
ertemp
erature.
It
protects
the
instrumen
t
by
causing the
regulated v
oltage supplies
to
b
e
shut
down.
It also
sends status
messages
to
the
A9
CPU
to
trigger
w
arning
messages
on
the
analyzer
displa
y
.
The
v
oltages
that
are
not
sh
ut
do
wn
are
the
+5VD and
+5VCPU
digital
supplies
from
the
preregulator,
the
fan
supplies,
the prob
ep
ow
er supplies,
and
the
displa
y
supplies. The
shutdo
wn circuit
can
b
e
disabled
momen
tarily
for
troublesho
oting
purp
oses
b
y
using
a
jump
er
to
connect
the
SDIS
line
(A8TP4)
to
ground.
Variable
Fan
Circuit
and
Air
Flo
w
Detector
The
fan p
o
w
er
is
deriv
ed
directly
from
the
+18
V
and
0
18
V
supplies
from
the
A15
preregulator.
The
fan
is
not
fused,
so
that
it
will
con
tin
ue
to
pro
vide airo
w and
co
oling
when
the
instrumen
t
is
otherwise
disabled.
If
o
v
erheating
o
ccurs, the
main
instrumen
t
supplies
are
sh
ut
do
wn and
the
fan
runs
at
full
sp
eed.
An
o
v
ertemp
erature
status
message
is
sen
t
to
the
A9
CPU
to
initiate
a
w
arning
message
on
the
analyzer
displa
y
.
The
fan also
runs at
full sp
eed
if
the air
ow
detector
senses
a
lo
w
output
of
air
from
the
fan.
(F
ull
sp
eed
is
normal
at initial
p
o
w
er
on.)
Displa
y
P
o
w
er
The
A8
assem
bly
supplies
v
oltages
to
the
displa
y
through
a
wire
cable.
The
A8
supplies
+5V
CPU
and
+65 V
to
the
A19
GSP
,
then
the
+65
V
is
routed
to
the
displa
y
.
They
are
not
connected
to
the
protectiv
e
sh
utdo
wn
circuitry
so
that
the A18
displa
y
assem
blies
can
op
erate
during
troublesho
oting
when
other
supplies
do
not
w
ork.
Probe
P
o
w
er
The
+18
V
and 0
18 V
supplies are
post
regulated
to
+15
V
and
0
12.6
V
to
pro
vide
a
p
o
w
er
source
at
the fron
t panel
for an
external RF
prob
e
or
milli-meter
mo
dules.
Digital Control
Theory
The digital con
trol functional group consists of the follo
wing assem
blies:
A1 fron
t panel
A2 fron
t panel pro cessor
A9 CPU
A10 digital IF
A16 rear panel
A18 display
A19 GSP
These assemblies combine to provide digital control for the entire analyzer and HP 85047A
and 85046A/B S-parameter test set. They provide math pro cessing functions, as well
12-6 Theory of Operation DRAFT
3/21/106 15:14
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HP 8753D Option 011 Specifications

General

Brand	HP
Model	8753D Option 011
Category	Measuring Instruments
Language	English