HP 8508A - Page 125

BERBER UE RRR eR SRR RRR eee ee eee
Service
ERROR
CODES
400
SERIES
Error
Codes
in
this
series
indicate
a
problem
with
the
Search
and
Lock
Assembly
rs
SEARCH
and
LOCK
ASSEMBLY
A4
Summary Description
The
function
of
the
Search
and
Lock
assembly
is
to
provide
an
optimally
selected
frequency
to
the
Sampling
Pulse
Generator
in
the
Input
Module.
This
frequency
is
generated
by
a
VCO.
The
assembly
operates
in
one
of
two
modes.
In
the
SEARCH
mode,
the
VCO
is
swept
and
the
output
of
the
Sampling
Gate
monitored
until
a
suitable
response
is
found.
At
this
point
the
processor
switches
the
board
into
the
LOCK
mode
where
the
VCO
is
tuned
to
phase
lock
the
IF
to
the
20
kHz
reference.
When
this
has
been
accom-
plished
the
system
is
able
to
make
measurements.
Troubleshooting
the
Search
and
Lock
Assembly
A
fault
in
the
Search
and
Lock
Assembly
will
be
indicated
by
an
Error
Code
display
in
the
400
series.
If
this
should
occur,
the
assembly
and
all
connections
should
be
checked
for
integrity.
The
adjustment
procedures
for
the
assem-
bly
should
be
carried
out
and
the
system
Self
Test
procedure
re-run.
If
the
assembly
still
proves
faulty,
it
should
be
replaced with a new one.
Disassembly
and
Reassembly
Procedures
Removing
the
Search
and
Lock
Assembly
To
Remove
the
Search
and
Lock
Assembly
from
the
Vector
Voltmeter:
a.
Wear
a
wrist
strap
for
ESD
protection.
b.
Remove
the
instrument
top
cover.
c.
Disconnect
the
cable
connections
from
the
Search
and
Lock
Assembly.
d.
Remove
the
8
Pozidriv
screws
that
secure
the
Search
and
Lock
Assembly
to
the
main
deck.
e.
The
Search
and
Lock
Assembly
can
now
be
removed
from
the
Instrument.
Refitting
the
Search
and
Lock
Assembly
Refitting
is
the
reverse
of
this
procedure.
Note
the
cable
connections
detailed
in
the
diagram
below.
E1089