YO Coil
Drive
Check with
Oscilloscope
Note
Use
the large
extender b
oard
for
easy
access
to
the
v
oltage
p
oin
ts.
The
extender
b
oard
is
included
with
the
HP 8753
To
ol Kit.
See Chapter
13,
\Replaceable P
arts," for
part n
umb
ers and
ordering information.
1.
Connect
oscilloscop
e
prob
es to
A11P1-1 and
A11P1-2. The
YO coil
driv
e
signal
is
actually
tw
o signals
whose
v
oltage
dierence
driv
es
the
coil.
2.
Press
4
PRESET
5
4
SYSTEM
5
N
NN
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
NN
NN
N
N
N
N
SERVICE
MENU
N
NN
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
NN
NN
N
N
N
N
N
N
N
SERVICE
MODES
N
NN
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
N
NN
NN
NN
NN
N
N
N
N
N
N
N
N
N
N
SOURCE
PLL OFF
to
op
erate
the
analyzer in
a
sw
ept
op
en
lo
op
mo
de.
3.
Monitor
the
t
w
o
YO
coil
driv
e
lines.
In
source tune
mo de
the v
oltage
dierence
should
v
ary
from
approximately
3.5 to
5.0 v
olts
as
sho
wn
in
Figure
7-7
.
If
the
v
oltages
are
not
correct,
replace
the
fault
y
A11
assem
bly
.
If
the
output
signals
from
the
A11
assem
bly
are
correct,
replace
the fault
yA3
source
assem
bly
.
If
neither
the A11,
nor the
A3 assem
bly
is
fault
y
,
con
tin
ue
with
the
next
c
hec
k.
Figure
VDIFF7 here.
Figure
7-7.
YO
0
and
YO+
Coil
Driv
e
V
oltage
Differences
with
SOURCE
PLL
OFF
A12 Reference Check
The signals
are ev
aluated with pass/fail c
hecks. The most ecien
tw
aytoc
heck the A12
frequency reference signals is to use the analog bus while referring to T
able 7-2 .
Alternatively,y
ou can use an oscilloscop e, while referring to T
able 7-3 and Figure 7-8 through
Figure 7-14. If any of the observed signals dier from the gures, there is a 90% probability
that the A12 assembly is faulty. Either consider the A12 assembly defective or perform the
\A12 Digital Control Signals Check."
Both of these pro cedures are described b elow.
DRAFT
3/21/106 15:13
Source Troubleshooting 7-11
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