Troubleshooting - Wavetek 3000 Instruction Manual

5 .4 TROUBLESHOOTING
Set MODE to FMxl_ and adjust M29-1 control
(B) to produce an output frequency that
is approximately 100 Hz above the CW
frequency .
Increase AM/FM Vernier to
maximum and adjust Modulation Board con-
trol (B) to increase frequency counter
reading by 5 kHz .
Set MODE to FMx100 and AM/FM Vernier to
maximum . Adjust M29-1 control (A)_°or a
frequency counter reading of
40 .500 MHz
±10 kHz .
Troubleshooting is generally a system-
atic procedure of "divide and conquer" .
A thorough understanding of the block
diagrams and-circuit description located
in Section 3 of this manual will enable
the trouble symptom to be localized to
a particular module or PC board .
Once
this has been accomplished the module
or board can be replaced, or repaired
with the aid of the proper schematic .
In general, it is preferable to replace
the module or PC-board assembly .
The front-panel ACCURACY lamps together
with the four internal module "unlock
indicator" lamps aid in troubleshooting
phase-locked loop problems . One module
in each loop contains an indicator lamp
which lights to indicate when that loop
is unlocked . The lamps indicate only
which loops are unlocked, but not which
module is at fault .
A problem in a power supply may cause
many symptoms pointing to other areas
and should be checked when the symptom
does not clearly indicate a specific
problem. The loss of the -18 V supply,
for example, will cause the
ACCURACY
lamp to flash ; while loss of the +18 V
supply will extinguish all lamps.
The
+18, -18 and +7 .3
V supplies comprise
the DPS2
power supply which forms the
rear panel of the instrument . Perfor-
mance of these supplies is indicated in
the CALIBRATION PROCEDURE .
For troubleshooting purposes, it is per-
missible to operate the Model 3000 with
any of the plug-in modules or RF cables
removed ; however, the instrument should
be turned off when removing or installing
modules . If substitute modules are
available, possibly from another Model
3000, this provides
an easy method of
verifying if a suspected module is de-
fective .
RF cables can be disconnected from the
module output connectors ; then a power
meter or spectrum analyzer can be con-
nected directly to the module connector
for power level or frequency measurements .
Fabrication of a short coax adapter
cable, terminated in a mating connector
for
the modules on
one end and a BNC
connector on the other, will facilitate
connection of test equipment .
Before engaging in a troubleshooting pro-
cedure,be sure front-panel controls are
set in proper operating position .
Make
a thorough visual inspection of the in-
strument for such obvious defects as
loose or missing screws, broken wires,
defective module-pin sockets, loose RF
cables and burned or broken components .
5 .4 .1
Troubleshooting Hints
MAINTENANCE
The following is a list of several typi-
cal symptoms followed by the probable
cause(s) or a troubleshooting procedure .
It is assumed the instrument has been
properly calibrated previously, and that
a
warmup period will precede
trouble-
shooting .
INTERMITTENT OPERATION - Defective mod-
ule-pin sockets or loose RF cables .
LOW RF OUTPUT (+10 dBm RANGE) - If power
is 10 dB low on this range but is cor-
rect on the 0 dBm range, Meter Board
micro switch S1 is probably not being
actuated by attenuator shaft .
LOW OR NO RF OUTPUT (ANY RANGE) - Defec-
tive attenuator or RF cables connecting
to input or output of attenuator, defec-
tive meter board, defective module MIOW
or M9W . Check voltage on pin 15 of mod
ule MlOW . The voltage should be approx-
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