Wavetek 3000 - Intermittent Operation; Low RF Output Issues; Output Meter Not Responding; Unleveled Lamp Issues

MAINTENANCE
5- 8
imately as follows : -2 .5 VDC on +10 dBm
range withVERNIER
fully clockwise ; -0 .7
VbC
on 0 dBmrange with VERNIER fully
clockwise .
These voltages indicate
proper
operation of the meter board ;
while
other
values, particularly posi-
tive voltages,indicate a defective IC
on

the meter board .

Next, checkRF
power directly at 1110W output .

If it
is correct, the trouble lies in the
attenuator or its RF cables . If module
M10W output is low, measure RF level
directly at module M9W output - this
should be approximately -10 to -11 dBm .
If
this level is correct, module M10W
is defective ; while if
the level is low,
Sweep
Oscillator
M9W is defective .
OUTPUT METER DOES NOTMOVE - If meter
is pegged at either end of scale, the
trouble is probablya defectivemeter-
driver IC on meterboard (C315) . If
meter remains at mechanical zero, meter
movementmay be open or a meter-board
IC is defective .
UNLEVELED LAMP ON - RF OUT connector not
terminated in 50-ohm load, AM percentage
set so that peak of modulated
output
exceeds
+13 dBm,
defectivemodule M10W,
defective attenuator or connecting RF
cables .
Connect power meter directly to M10W
output . Set OUTPUT dial and VERNIER
for a +13 dBmreadingon power meter at
50.000 MHz .

Step throughfrequency range
from 10 to 520 MHz in 10 MHz-steps .

A
powermeterreading of +13 dBm ±0 .5 dB
withUNLEVELED lamp OFF indicates proper
operation of moduleM10W .

Connect power
meter directly to attenuator
output
and
repeat above steps .

If
attenuator output
is correct, trouble is due to a defec-
tive RF cable or possiblya poor ground
connection at RF OUT connector . If out-
put is correct at MlOW but the UNLEVELED
lamp is ON, the trouble is probably a
defective lamp-driver circuit in module
M10W .
ACCURACYLAMPS FLASH CONTINUOUSLY - A
steady light in CW mode but flashing
lights in FM modes indicate
a defective
M29-1 or
M33 module .

If
ACCURACY lamps
flash in all modes, one or more of the
phase-locked loops is open ; see PHASE
LOCKEDLOOPTROUBLESbelow . NOTE :

Above
the normal
frequency
range of the instru-
ment (in the vicinity of 560 MHz), it is
normal for phase-locked loop #4 to un-
lock causing thelamps to flash .
PHASE-LOCKED LOOP TROUBLES - An open or
unlocked loop, indicated by a lighted
module lamp, canbe caused by
a
number
of factors, including : low AC-input vol-
tage, lowDC-supply voltages, improper
phase-locked loop DC voltages, an open
or shorted RF cableor a defective
mod-
ule .
A defective RF cableor modulecan have
a chain-reaction effect that

causes
two or more loops to unlock .

For example,
loss of the 1 kHz signal to moduleM31
willcause PLL
#1
to unlock ; thus, module
M31
may not supply
a
proper
signal
to
module
M34,
causing PLL
#4 to
unlock .
Failure of the
40
MHz crystal oscillator
in moduleM30 will cause all
four loops
to unlock, sinceall
six
reference fre-
quencies willbe lost .
Table 5-2 lists typicalRF signal-input
levels for each of the phase-locked
loops . Those signals having a TTL level
or 1 V level maybe measuredwithahigh-
frequency oscilloscope ; the other signals
are bestmeasured with aspectrum analy-
zer . NOTE : TheTTL waveform shown in
Table 5-2 is for illustration of voltage
values only, and does not necessarily
represent the observedwaveshape .
Phase-Locked
Loop#1
-
Unlocking
of
this
loop maybe caused by a defectivemodule
M31, moduleM30 or RF cable connecting
M30 to M31 .
If M31A unlockindicator is on, check 1
kHz signal as listed
in Table 5-2 .
If
1 kHz signal is correct, module M30

is
operating properly, then

check RF cable
between M30

and
M31A
. If proper 1 kHz
signal is beingapplied to M31A, check
for 7
.3
V on pin 6, +18V on pin
7,
and
-18 V
on pin 8
of
M31A,
If
input signal