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Model
2001
MAINTENANCE
other areas and should be checked when the symptom does
not clearly indicate a specific problem. The +18, -18, and
-20V supplies are located on the rear chassis printed circuit
board and the +16 and -16 reference voltage supplies are
located in the M2H module. Performance of these supplies
are indicated in the calibration procedure.
5.6.1 TROUBLE SHOOTING HINTS
The following is a list o f several typical symptoms followed
by the probable cause or a trouble shooting procedure.
INTERMITTENT OPERATION OF ANY TYPE - Defective
module pin sockets or loose RF cables.
selector switch. See the calibration procedure for verifying
proper operation.
NO RF SWEEP
-
First check pin 12 of the M1H module
for the presence of a 32V ramp.
This ramp indicates
proper operation of the M1H. Next check for the ramp at
the input of the M2H pin
7
( A F mode). Finally check
the output of the M2H at pin 9. I t should be similar t o the
input except it will be lower in amplitude, approximately
12V peak-to-peak, and will have an average value of OV
when the Front Panel center frequency control is set t o
mid-band. I f the M2H output is correct the trouble would
probably be in the M9H or M19H sweep oscillator module.
MARKER PROBLEMS
NO RF OUTPUT
A L L THREE BANDS - Defective attenuator or RF
cables connecting t o the input or output of the attenuator.
SINGLE BAND ONLY - Check for the presence of the
band switching voltages 6-1, B-2, and B-3 at module M9H,
MIOH, and M19H a s shown on the Module Wiring Diagram.
RF OUTPUT NOT FLAT - Most common cause is the ex-
ternal RF detector being defective. Another is the monitor
diode located in the M19H module. This is a point contact
diode and can be damaged if the RF output is momentarily
connected t o a B+ voltage. A good monitor diode will pro-
duce a negative detected voltage (pin 8 of M19H) approxi-
mately twice the amplitude of the external detector. For
example, at an RF output of +10dBm an external RF
detector will read approximately 0.8V. The internal moni-
tor,
pin 8 of M19H, will read approximately -1.6V.
FREQUENCY UNSTABLE (JITTER)
-
Check all modules
for loose hold-down screws, especially module M2H.
Check the
+
and -16V reference supplies. Operating the
unit in a strong magnetic field, such as setting on top of or
adjacent to another instrument containing a large power
transformer, can produce 60Hz HUM modulation.
SWEEP RATE PROBLEM - Probable cause is a defective
M1H module or wiring to the Front Panel SWEEP TIME
To isolate the cause of a marker problem when the symptom
does not clearly indicate a specific circuit or component,
first check the sweep sample output at the M5H Sweep
Sample Out connector.
I t should be a detected signal be-
tween 30 to 50 mV. If the proper sweep sample signal is
not present i t indicates that the trouble is in the sweep
oscillator module or connecting sweep sample cables. Next
connect the detector in place of the terminating plug P102.
A signal at this point indicates all jumper cables and RF
jacks on the M6 modules are intact. Then check for the
birdy output at pin 3 of the marker module. A 10 t o
15mV peak-to-peak birdy is sufficient t o drive the M5H
module and indicates the M6 module is operating properly.
With the 15mV peak-to-peak birdy present at the input of
the M5H, pins 1, 2, 3, or 4, a 32V peak-to-peak signal will
be produced at the output pin
7.
This indicates proper
operation o f the M5H. This output signal at pin
7
is con-
trollable in width by the Front Panel MARKER WIDTH
control. The signal is now routed through the Front Panel
Marker Size control and to the Front Panel SCOPE
VERTICAL connector. A 12V peak-to-peak signal is nor-
mally at this point when the Front Panel SIZE control is
set to maximum.
A common marker problem is that
caused by one of the interconnecting cables between the M6
modules being loose.
This causes a notch in the sweep
sample input t o the module causing uneven harmonics or
weak output.
Model
2001
other areas and should be checked when the symptom does
not clearly indicate a specific problem. The +18, ·18, and
-20V supplies are located on the rear chassis printed circuit
board and the + 16 and -16 reference voltage suppl ies are
located in the M2H module. Performance of these supplies
are indicated in the calibration procedure.
5.6.1 TROUBLE SHOOTING HINTS
The following is a list of several typical symptoms followed
by the probable cause or a trouble shooting procedure.
INTERMITTENT OPERATION OF ANY TYPE - Defective
module pin sockets or loose RF cables.
NO RF OUTPUT
ALL THREE
BANDS -
Defective attenuator or RF
cables connecting to the input or output of the attenuator.
SINGLE BAND ONLY - Check for the presence of the
band switching voltages B-1, B-2, and B-3 at module M9H,
M 1 OH, and M 19H as shown on the Module Wiring Diagram.
RF OUTPUT NOT FLAT - Most common cause is the ex-
ternal R F detector being defective. Another is the monitor
diode located in the M19H module. This is a point contact
diode and can be damaged if the RF output is momentarily
connected to a B+ voltage. A good monitor diode will pro-
duce a negative detected voltage (pin 8 of M19H) approxi-
mately twice the amplitude of the external detector. For
example, at an R F output of + 1 OdBm an external R F
detector will read approximately O.BV. The internal moni-
tor, pin 8
of M19H, will read approximately -1.6V.
FREQUENCY UNSTABLE (JITTER) - Check all modules
for loose hold-down screws, especially module M2H.
Check the + and -16V reference supplies.
Operating the
unit in a strong magnetic field, such as setting on top of or
adjacent to another instrument containing a large power
transformer, can produce 60Hz HUM modulation.
SWEEP RATE PROBLEM - Probable cause is a defective
M1H module or wiring to the Front Panel SWEEP TIME
MAINTENANCE
selector switch. See the calibration procedure for verifying
proper operation.
NO RF SWEEP - First check pin 12 of the M1H module
for the presence of a 32V ramp.
This ramp indicates
proper operation of the M1H. Next check for the ramp at
the input of the M2H pin 7 (aF mode).
Finally check
the output of the M2H at pin 9. It should be similar to the
input except it will be lower in amplitude, approximately
12V peak-to-peak, and will have an average value of OV
when the Front Panel center frequency control is set to
mid-band. If the M2H output is correct the trouble would
probably be in the M9H or M19H sweep oscillator module.
MARKER PROBLEMS
To isolate the cause of a marker problem when the symptom
does not clearly indicate a specific circuit or component,
first check the sweep sample output at the M5H Sweep
Sample Out connector.
It should be a detected signal be-
tween 30 to 50 mY. If the proper sweep sample signal is
not present it indicates that the trouble is in the sweep
oscillator module or connecting sweep sample cables. Next
connect the detector in place of the terminating plug P1 02.
A signal at this point indicates all jumper cables and RF
jacks on the M6 modules are intact.
Then check for the
birdy output at pin 3 of the marker module.
A 10 to
15mV peak·to·peak birdy is sufficient to drive the M5H
module and indicates the M6 module is operating properly.
With the 15mV peak-to-peak birdy present at the input of
the M5H, pins 1,2,3, or 4, a 32V peak-to-peak signal will
be produced at the output pin 7.
This ind icates proper
operation of the M5H. This output signal at pin 7 is con-
trollable in width by the Front Panel MARKER WIDTH
control. The signal is now routed through the Front Panel
Marker Size control and to the Front Panel SCOPE
VERTICAL connector. A 12V peak-to·peak signal is nor-
mally at this point when the Front Panel SIZE control is
set to maximum.
A common marker problem is that
caused by one of the interconnecting cables between the M6
modules being loose.
This causes a notch in the sweep
sample input to the module causing uneven harmonics or
wea k ou tpu t.
5-13
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