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I
a.
lf.b€at
notes
are present,
press
HELP
to
enable
the lock.
Check
the-
Error'
Amplifiei
output
at
T?2O3T,
on
th€
Error
Amplifier
OolrJln
the
prrase
Lock
module.
gutput
signat
amptituOe'sfroufO
Oe
approximately
6 V
peak-peak
aho
its
frequency
should
be
10
Hz.
fhe
up
anO
Oown-oui.t_r"ng"
:igngj:,
on
edge
connectors
g
and
10
oi
tn"
error.
Amplifier
board,
shoutd
be
toggling
Oetween
0 V and
+5
V.
(1)..1f
there
is
a
signat
at Tp2O37
but
one
or
both
or
tne out-of-range
lines
is
not
toggling,
the out-
of-range
comparator
on
the
frior-
Amptifier
board,
or
the
sensing
circuit
on
the
phase
Lock
Controt
board,
has
probabty
failed.
firis
coutO
cause problems
in
maintaining
lock
but
not
in
acquiring
lock.
lf
the
instrument
does
not
acquire
lock.
note
the
out-of_range
problem
and
continue
troubteshooting
with
steF
gj.
(2)
lf
there
is
no
signal
at
Tp20g7,
the
Error
Amplifier
has probabty
failed.
(E)
(3)
ff
there
is
a
signal
atTp2A}Z,
th€
switching
circuit
that
connects
the
output
of
the
Error
Amplifier
to
th€
FM
coil
of
tne
i st
LO
has
prob_
ably
failed.
(E)
P
lf
b€at
notes
arg
present,
but
their
amplitude
is
::::_^T"l !:9
v (peak-peak),
or
the
amptitude
qrnerence
of
the
positive
and
negative
sxcursions
is
more
than
2AVo,
the
phase
GatJ
is
probably
defec-
tive. (E)
c.
lf
there
are
no
beat
notes,
mEasure
the
strobe
frequency,
at
p504
on
the
phase
l_ocf
moOuie.
(1)
lf
the
strobe
frequency
is
the same
as
the
readout
on
the
diagnostic
aiO
display,
it
is
possi_
ble,
but
not
probable,
that
the
r it
[o
system
is
miscalibrated
and
that
th€ lst
LO
is
near
tne
wrong
harmonic
of
the
Auxiliary
Synthesizer.
Press
<Blue-SHIFT>
to return
to'normat
opera-
tion and
look
at
the calibrator
line
that
is
ctosest
in. frequency
to
the
frequency
(in
Band
1) at
which
the
error
occurs.
lf
the irequency
indi_
cated
for
the
calibrator
line
is correci
(a
multiple
9t..
tlO
MHz),
the
phase
cate
has
proOa-Uty
failed.
lf
the frequency
indicated
is incorrect,
attempt
to
calibrate
the
1st
LO
system
by
pressing
<Blue-
SHIFT>
PULSE
STRETCHER-
and
sete-cting
#1
(FREQUENCY
LOOPS
CAL),
and
tben
#O
(OVERALL
SYSTEM)
from
the rnenu.
Exit
from
the
calibration
routine
when
the
display
for
R4040,
on
the
CF.
_C*ontrol
board
appears
by
pressing
<Blue-SHIFT>.
lf
the
calibration
can
not
b€
completed,
or
it
does
not
rEsult
in
the
correct
frequency
indication
for
the
calibrator
rine,
troubleshoot
the
lst
LO
system
using
the
procedure
under
TUNTNG
FAIiURE
_rst
LO
error
message
step
3b.
(E)
Malntenance
-
4g4Ll4g4Ap
Service
Vol.
1
(2)
lf
there
is
no
strobe
signal,
check
for
a
sig-
nal
on
feedthrough
M,
on
the
Strobe
Driver
board
in
the Phase
Lock
module.
(a)
lf
there
is a
signat,
the
Strobe
Driver
has
probably
faited.
(E)
(b)
lf
there is
no
signat,
the
Controiled
Oscit-
lator
has
probably
faited. (E)
(3)
lf
the
frequency
of
the
strobe
signal
is
effoneous.
but
is
stable (within
1_2
Hz), in
the
normal
strobe
range
of
5.006477
MHz
to
5.018868
MHz,
the
programmabte
divider
in
the
Synthesizer
has
probabty
faited. (E)
(4)
lf
the listed
Strobe
Freq
is
betow
5.OOZ10O
MHz
and
the
actual
strobe
frequency
is slightly
above
th€
desired
frequency;
orabove
5.01g240
MHz
and
the actual
strobe
frequency
is
slightly
below
the
desired
frequency,
attempt
to
cali_
brate
the Phase
Lock
Synthesizer.
press
<BIue-SHIFT>
PULSE
STRETCHER
and
select
#1,
then
#5.
lf
you
are
able
to
complete
the
calibration,
check
to see
if
the error
message
is
still
present.
lf it
is stilt
displayed,
or
the
calibra_
tion
routine
could
not
be
completed,
proceed
to
th€
next
step
as
if
th€ strobe
frequency
was
not
within
the above
range. (E)
(5)
lf
the listed
Strobe
Freq
is
outside
the
range
in
th.e
pr_ejgding
step,
measure
the
tune voltage
for
the VCO,
at feedthrough
H on
the
Controll€d
Oscillator
board
in
the
phase
Lock
module.
The
normal
range
is from
5.9 V
to
11.3
V.
With
the
loop
unlocked,
the voltage
wiil
probably
be near
or
beyond
one end
of
the range.
(a)
lf
the voltage
is around
the
center
of
the
range,
the loop
filter
and
amplifier,
on
the
Error
Amplifier
board,
are
probably
at fault.
(E)
(b)
lf
the
tuning vottage
and
the strobe
fre-
quency
are
displaced
from
the
center
of
their
range (8.6
V and
5.013
MHz) in
the same
direction,
the VCO
is
good
and
something
else
within
the loop
has faited.
(E)
(c)
lf
the
tuning voltage
and
the strobe
fr€-
quency
are
displaced
in opposite
directions
from
the center
of
their range,
th€
VCO
has
probably
faited. (E)
6-13