Table of Contents
Advertisement
N
ext, chec k RF power directly at t h e ΜΙΟ W δ/Θ output .
If it
is correct. th e ιrηιι 6Ιe lies in the Attenιι ator or its
RF ca bles . If the mo d ule Μ 10W -6/8 ου tρυ 1 is low, measure
t
he
m
odu le Μ9W RF output - this should be approxi-
mately -10 to 11 dB m .
Ι 1
t
his level is cor rect, module
Μ 10Wδ/8 ί5
d
efective ; while if the level is low, Swee.p
Oscillator ΜgW is defective .
O UTPUT M ET ER DO E S NOT
M
OVE - If
t
he METER is
pegged at either end of scale. the trou ble is probably a
d
efective co mp onent on
M
eter Boa r d ε 315 ; w h ile if the
ME TER remains at mechanical zero, t h e Μr ΤΕ R move-
ment
m
ay be open or α M eter Boa rd component
m
ay be
d
efective .
U
NL EVELED
L
AMP ON - β F O UT connector not ter
mi nated in 50 ohm load, AM percentage set so that peak ο!
m
odulated output exceeds +13 dBm,
d
efective
m
odu le
Μ 10W δί8,
d
efective Αιινηυατοr or connecting RF εα bΙστ .
Connect α power meter
d
irectly to the Μ IO
W
-6 8 output .
Set the OUTPU T $Ιπρ ηιιιf VERN I ER controls for α +13
dBm reading on ιhe power rneter at 50-000 ΜΗτ . Step
throug h the 10 to 520 MHz frequ ency range in 10 MHz
steps. Α power motor reading of +43 dB m }0 .5
d
B with
t
he
UNLEVE LE
D
lam p off indicates proper operation of
m
od u le M 10W-6 ./8. 11 the Output is correct at MloWr6!8,
but the UNLEVELE D la mp is on, the trouble is
p
robably α
d
efective la mp driver circuit in module Μ 10W δ/Β. With
pr op er operation of module Μ 10W-6/8, connect the power
meter
d
i rectly to the Step Attenuator output and repeat
t
he above steps. If t h e Αττεηυατοι ηιιιηιιι is correct, the
t
rouble is d ue to α
d
efective RF cahlk, ηι possibly α
p
oor
groun d connection α 1
β
F Ο U Τ εηππ ec τοι ,
ACC
UR
ACY
LAMP
FL
AS
HE
S CO
N
TI
NU
O
U
S
L
Y - Α
stea dy lig h t in CW mode
b
ut flas h ing in FM modes indicates
α
d
efective Μ29 .2
o
r Μ 33-2 mo du le . If ιιι e ACCU RACY
lamp flashes in all modes . one or
m
ore of the phase-locked
loops is open ; see Ph ase- Loc ked
L
oop Troubles
b
elow .
ΝΟΤΕ
A
bove the normal fre que ncy range of the instrument (in
t
h e vicinity of 560 ΜΗτ ), it
is normal for phase-locked
loop 4 to
u
nlock, causing the ACCUR ACY lamp to flas h.
PH AS E-LOCKE D
L
OO P
T
ROUBLE S - An open or on
lock ed loop, indicated by α lig h te d module lam p, can be
ca use d by α
n
um b er of factors, including, low AC input
voltage, low DC su pp ly voltages, i mp ro per phase locked
loop DC voltages, an open or s h orte
d
RF ca ble, or α de-
f ective
m
odule.
Α defective RF ca ble or module can
h
ave α "c hai n reaction 11
effect th at causes two o r m ore loops to unlock . For
exam ple, loss ο!
t he 1 kH z sign al to mo du le M31A will
cause PLL 1 to
u
nloc k ; thu s, module Μ31 Α may ηοτ sup ply
α proper τί gπαΙ 1ο mo dule Μ34, causing PLL 4 to un lock .
F
ailu re of the 40 MHz Crystal Oscillator in
m
odu le Μ 30-1
will cause all loops (υ un lock , since all six
r
eference fre-
quencies will be lost,
Ta ble 51 lists ty pical RF signal-inpu t levels for eac h of
the phase-locked loops, Those signals
h
aving α TT L level
or 1 V level may be
m
easu re d with α
h
igh-f requ ency
oscillosco pe; the ot h er signals are best measur ed with α
spec τr ιι m analyzer (dB
M
), or α 50 ohm
d
etector and εαΙ" -
brate d scope ImV)
ΝΟΤΕ
T
h e TT L waveform shown in Ta b le 5.1 is for illustration
of voltage
v
alues only,
a
nd does not necessarily re present
t h e observed wave-shape.
PHASE-LOCKED
L
OO P 1 -
U
nloc k ing ο ! this loop may
4ς ι . αιιερι 1
b
y α defec ηνι.
Μ31 Λ, ιπο
d
υΙ e Μ30-1 υ,
RF cable connecting Λ 430-1 [ ο M3) A.
If the Μ31 Α unlock indicator is on, chec k the 1 kH z signal
.as listed -η Table 5-1 . If the 1 kH z sign al is co rrect, module
Μ3Π 1 is operating property . Ch ec k
t
he RF cable
b
etween
ΙΠ 30- Ι and Μ31 Α. If
t
he
p
roper 1 kH z signal is being
applied to the Μ3 ΙΑ , chec k for +7 .3 V on
p
i n 6, +18 V on
pin 7. and -18 V on pin 8 of Μ31 Α. If the i n put signal and
DC voltages are correct, mo du le Μ 31 Α is defective .
PII Α SF - LOC KE D
L
OOP 2 - Unlocking of loop 2 can be
εαυτει l by defective modules MI 72, M30 1 . M32A or RE
cables connecting Μ 30-1 το Μ32 Α.
Connect α digital voltmeter to Μ 32 Α pin 11 and observe
th e rea d ings while stepping throug h
t
he 200 to 239 MHz
freg ιι ency range in 1 MHz steps. The voltmeter
r
ead ing
should ch a n ge -02 V per MH z from 0 V at 200 MHz to .7 .8
V at 239 MHz. These voltages i n
d
icate
p
ro per operation
of module Μ 172.
Μπι1 ιι 1~ Μ30-1 Can tie chec
k
ed by measuring the I MHz and
1440 MH z signals
d
irectly at the. M30-1 . The levels stpecified
in Τα 6Ιει 5-1 in dicate pro per operation of module M30-1
C hιick connecto r s and RF cables connecting M30 I in
module Μ32 Α, Chec k to, ω 1$ V on pin 7, -18 V on pin 8,
and +7 .3 V on ρί r ι 9 of Μ32 Α. If all i nput sig nals and DC
voltages to module Μ 32 Α are no rmal,
b
ut t h e Μ 32 Α LE D
is on . module Μ 32 Α is
d
efective-
PHAS E-LOC KE D
L
OO PS 3 and 5 - T h e LE D indicator
on modu le Μ33-2 se rves bot h PLL 3 and PLL 5. If the
Μ33-2 LE D is on,
d
etermine- w h ic h loop is
d
efective
b
y
switc
h
ing
the FREQUENCY VERN IER out of CA L
position, If t h e Μ33-2 LE D goes off, the trou ble is in PLL
5; if th e LE D stays on . the τιου b Ιe is in PLL 3.
5- 7
Advertisement
Table of Contents
