TM 11-6625-2781-14&P-2
TEST PROCEDURES:
SERVICE SHEET 8
1-a. Connect Oscilloscope to Test Point A and observe
1.
Trouble isolated to summing/shaping of first local
waveform shown below.
oscillator tuning voltage, preset scan amplifier, or
marker generator circuits.
2.
It is assumed that procedures in Paragraphs 5-23
CONTROL SETTINGS:
Oscilloscope:
conducted, that preceding tests were satisfactory, and
.2V/Div
that proper dc operating voltages are present.
5 msec/Div
10:1 probe
TROUBLESHOOTING PROCEDURES
Analyzer:
1.
If trouble has been localized to the first local
PER DIVISION
oscillator summing or shaping circuits remove Voltage
2 msec/Div
Control Assembly A5 and install it in the troubleshooting
10 MHz/Div
position using extender card HP 11592-60011.
Waveform GOOD: proceed to step 1-b.
Waveform BAD: Input signal not correct or Q7, C2 or
2.
Follow procedural steps shown under circuit
R3 may be defective.
1
2
3
theory for steps
,
, and
.
1-b. Connect Oscilloscope across R9 and observe
3.
If trouble has been localized to the preset scan
waveform shown above.
amplifier or marker generator circuits, remove preset
scan assembly A4 for maintenance.
CONTROL SETTINGS: Same as 1-a.
4.
Follow procedural steps shown under circuit
Waveform same as 1-a. GOOD: proceed to step 1-c.
5
4
theory for steps
and
.
BAD: APC signal not correct or Q7 circuit may be
defective. Also check Q6 and feedback circuits.
EQUIPMENT REQUIRED
1-c. Connect Oscilloscope to Test Point C and observe
waveform shown below.
Service Kit ................................ ............ HP 11592A
Oscilloscope........................ HP 180A/1801A/1821A
CONTROL SETTINGS: Same as 1-a.
Digital Voltmeter .......................... HP 3440A/3443A
Waveform GOOD:
Proceed to step
2
CONTROL SETTINGS
As specified in individual tests.
Waveform BAD:
1
Check Q5/Q6
FIRST
LOCAL
OSCILLATOR
SUMMING
and associated
AMPLIFIER
components
Operational amplifier Q5/Q6/Q7 sums tuning voltages to
control the operating frequency of the first local
NOTE:
oscillator. Attenuated ramp voltages from the scan
If the FREQUENCY control is suspect
width voltage divider and dc tuning voltage from the
FREQUENCY control tune the analyzer in ZERO and
as a source of trouble, set SCAN
PER DIVISION scan width modes. When the analyzer
WIDTH to 0-100 MHz and rotate the
is stabilized in narrow scan width modes an APC voltage
tuning control throughout its range
is also applied as an offset voltage to maintain
while monitoring the dc level at Test
frequency dial and display accuracy. The output of the
Point C. 0 MHz = OV, 110 MHz =
operational amplifier is a symmetrical scan ramp
14.28V.
centered on the dc level set by the FREQUENCY
control. The ramp amplitude is determined by the scan
2
FIRST
LOCAL
OSCILLATOR
SHAPING
width voltage divider.
The FREQUENCY control
AMPLIFIER
determines center frequency on the display; SCAN
The main frequency determining component in the first
WIDTH PER DIVISION determines the bandwidth of the
local oscillator, a varactor, is not a linear device; it
signals to be displayed. In the 0 to 100 MHz scan width
requires an exponential voltage ramp to produce a
mode the summing amplifier is switched out of the first
linear change in frequency in respect to time.
local oscillator circuit. Tuning range adjustment R13
Operational
amplifier
Q2/Q3/Q4
provides
an
provides dial calibration capability.
exponential ramp output when a linear ramp is applied
to the input. This insures that the CRT display is linear
in the frequency domain. Voltage
