HP 5254C Service manual

HP
5254C
OPERATING AND SERVICE MANUAL
FREQUENCY
CONVERTER
S254C
rzcn 5254C FREQUENCY CONVERTER .15-3.0 GHz
HEWLETT *PACKARD
HEWLETT[hp, PACKARD
M

CERTIFICATION
The Heivlett-Packard Company certifies that this instrument teas
thoroughly tested and inspected and found to meet its published
specifications when it teas shipped from the factory.The Hewlett-
Packard Company further certifies that its calibration measure-
ments are traceable to the U.S. National Bureau of Standards to
the extent allowed by the Bureau's calibration facility.
WARRANTY AND ASSISTANCE
All Hewlett-Packard products are warranted against defects in
materials and workmanship. This warranty applies for one year
from the date of delivery, or, in the case of certain major compo-
nents listed in the operating manual, for the specified period. We
will repair or replace products which prove to be defective during
the warranty period provided they are returned to Hewlett-
Packard. No other warranty is expressed or implied. We are not
liable for consequential damages.
Service contracts or customer assistance agreements are available
for Hewlett-Packard products that require maintenance and re-
pair on-site.
For any assistance, contact your nearest Hewlett-Packard Sales and
Service Office. Addresses are provided at the back of this manual.

FREQUENCY CONVERTER
5254C
r
SERIALS PREFIXED: 1124A
This manual applies directly to HP Model
5254C Frequency Converter having serial
prefix number 1124A. See Paragraph 1-7.
MODELS 5254A &5245B
This manual with information provided in
Section VII also applies to Model 5254B
Frequency Converter having serial prefix
number 952-, 712-, 514-, 429-, and 415.
Copyright HEWLETT PACKARD COMPANY 1964
5301 STEVENS CREEK BLVD .SANTA CLARA. CALIF 95050
Printed: SEP 1971
HEWLETT iho PACKARD

Table of Contents Model 5254C
TABLE OF CONTENTS
Section Page
I
II
GENERAL INFORMATION .. .
1-1. Description
1-5. Specifications
1-7. Instrument Identification
1-9, Cooling
INSTALLATION
2-1. Introduction
2-3. Unpacking and Inspection . .
2-5. Storage and Shipment ....
2-8. Installation
2-11. Power Requirements .
2-13. Electrical Connections
III
IV
V
OPERATION
3-1. Introduction
3-3.Controls and Input 3”j
3-9. Maximum Input Voltages
3-H. Frequency Measurement with Amplitude less than 50 Mv rms ..3-1
3-13. Double Checking Frequency Measurement Result 3-2
3-16. Aid to Rapid Tuning 3"2
PRINCIPLES OF OPERATION
4-1. General
4-5. Multiplier Amplifier A1
4-7. Harmonic Generator A2and Harmonic Selector Cavity
4-9. Filter Assembly A4
4-11. Mixer Assembly A3
4-13. Video Amplifier A5
4-1
4-1
4-1
4-1
4-1
4-1
4-3
MAINTENANCE
5-1. Introduction
5-3. Periodic Maintenance
5-5. Test Equipment
5-7. In-Cabinet Performance Check
5-9. Troubleshooting
5-11 .Multiplier Amplifier Assembly A1
5-13. Mixer Assembly A3
5-15 .Video Amplifier Assembly A5
5-17. Repair and Replacement
5-18. General
5-20. Printed Circuit Component Replacement. . ,
5-22. Multiplier Amplifier Assembly A1
5-24. Harmonic Generator Assembly A2
5-26. Harmonic Selector Cavity
5-28. Mixer Assembly A3
5-30. Filter Assembly A4
5-32. Video Amplifier Assembly A5
5-34. Meter Replacement Procedure
5-36. Circuit Adjustments
5-38. Crystal Filter Adjustment
5-40. Mixer Balance Adjustment
5-41. Low Pass Filter Adjustment
5-43. Meter Amplifier High Frequency Adjustment
5-1
5-1
5-1
5-1
5-1
5-1
5-1
5-1
5-2
5-2
5-2
5-2
5-2
5-2
5-3
5-3
5-3
5-3
5-3
5-3
5-5
5-5
5-5
5-7
VI REPLACEABLE PARTS .
6-1. Introduction
6-4. Ordering Parts ...
6-1
6-1
6-1

Model 5254C Table of Contents
TABLE OF CONTENTS
Section
VII MODEL 5254A and 5254B
Introduction
Description
Specifications
Operating Procedure
Adjustments
In- Cabinet Performance Check
Troubleshooting
Older HP 5254A Instruments
Multiplier Amplifier Assembly A1 ..
Harmonic Generator Assembly A2 and
Harmonic Selector Cavity
Mixer Assembly A3
Filter Assembly A4
Video Amplifier A5
VIII CIRCUIT DIAGRAMS
8-1.Introduction
LIST OF ILLUSTRATIONS
7-1.
7-6.
7-8.
7-10.
7-12.
7-14.
7-16.
7-18.
7-20.
7-22.
7-24.
7-26.
7-28.
Page
•7-1
•7-1
7-1
•7-1
7-1
7-1
7-2
7-2
7-2
7-3
7-3
7-3
7-3
7-
3
.8-1
8
-
1
1-1.
3-
1.
4-
1.
4-2.
4-3.
5-1.
5-2.
7-1.
7-2.
7-3.
7-4.
7-5.
7-
6.
8
-
1.
8-2.
8-3.
Model 5254C and Accessories
Model 5254C Operating Procedure 3_3
Model 5254C Block Diagram
Multiplier Amplifier Assembly Al, Harmonic Generator
Assembly A2, and Harmonic Selector Cavity, Block Diagram. .4-2
Low- Pass Filter Assembly A4, Mixer Assembly A3, and Video
Amplifier Assembly A5, Block Diagram 4_2
Spectrum Analyzer Display 5_5
Top and Right Side View (5254C) ’*’’*’‘‘
'5_6
Model 5254A Operating Procedure 7_2
Cavity and Left Side View (5254A) ‘‘’
7_4
Top and Right Side View (52 54A) 1-5
Multiplier Assembly Al, and Video Amplifier Assembly A5
Component Location (5254A)
Multiplier Assembly Al, Harmonic Generator A2, Schematic. ...7-7
Filter Assembly A4, Mixer A3 and Video Amplifier A5 Schematic. 7-9
Schematic Diagram Notes
Multiplier Amplifier Al, Harmonic Generator A2, Schematic. ...8-3
Filter Assembly A4, Mixer Assembly A3, and Video Amplifier’
*
Assembly A5, Schematic o_c
LIST OF TABLES
1-1. Specifications ..1 1
3-1. Frequency Resolution. 31
3-2. Typical Double-Check Frequency Measurement 3-2
5-1. Recommended Test Equipment 5-0
5-2. Assembly Designations 5-1
5-3. Mixer Resistance Check 61
5-4. In -Cabinet Performance Check 57
6-1. Reference Designation Index ...62
6-2. Replaceable Parts
.
fi Q
6-3. Manufacturer’s Code List . . 6-13
7-1. Specifications for 5254A 71
7-2. Troubleshooting Aids (Model 52 54A) 7-8
7-3. Reference Designation Index (Model 5254A) 7-10
7-4. Replaceable Parts (Model 52 54A) 7-16
8-1. Troubleshooting Aids (Model 5254C) .8-2
iii

Section IModel 5254C
j; :
:v
m•V'w
:
*
mSSi*. 3M
•V 'ft
V".-
IMS
B

Model 5254C Section I
SECTION I
GENERAL INFORMATION
1-1. DESCRIPTION.
1-2. The Hewlett-Packard Model 5254C Frequency
Converter is aplug-in unit which extends the frequency
measuring capability of an HP Electronic Counter rrom
.15 to 3. 0GHz (150 MHz to 3000 MHz).
1-3. The stability and accuracy of the basic counter
are retained by multiplying a10-MHz signal, derived
from the 1-MHz internal time base of the counter, to
50 MHz and selecting aharmonic frequency between 200
and 2950 MHz. This known harmonic of 50 MHz is then
heterodyned with the INPUT signal. The resulting dif-
ference frequency, if between 1MHz and 53 MHz (band-
width of amplifier in plug-in) is counted and displayed
by the counter. The frequency of the INPUT signal is
then indicated by the combination of the MIXING FRE-
QUENCY control (in gigahertz; front panel of plug-in)
and the digital display of the counter (in megahertz).
1-4. Afront panel meter, by monitoring the differ-
ence-frequency output of the plug-in to the counter,
aids in selecting the desired MIXING FREQUENCY
and also in determining if INPUT signal amplitude is
adequate for accurate frequency measurement.
Table 1-1.
1-5. SPECIFICATIONS.
1-6. Table 1-1 contains all technical specifications
for the Model 5254C when operated in the HP Elec-
tronic Counter.
1-7. INSTRUMENT IDENTIFICATION.
1-8. Hewlett-Packard uses atwo-section serial
number mounted on the rear panel. Earlier instru-
ments use an 8-digit serial number (000-00000). The
first three digits are aserial prefix number: the last
five digits refer to the specific instrument. Later in-
struments use a9-digit serial number (OOOOAOOOOO).
The first four digits are the serial prefix and the last
five digits refer to the specific instrument. If the
serial prefix of your instrument differs from that
listed on the title page of this manual, there are dif-
ferences between this manual and your instrument.
Lower serial prefixes are documented in Section VII,
and higher serial prefixes are covered with manual
change sheets included with the manual. If the change
sheet is missing, contact the nearest Hewlett- Packard
Sales and Service Office listed on the inside real’
cover of this manual.
1-9. COOLING.
1-10. The Model 5254B is cooled by the ventilation
system of the counter in which it is installed. See
the service manual of counter for cooling system and
maintenance instructions.
Specifications
OPERATING FREQUENCY RANGE: 0. 15 to 3GHz (0. 2to 3 GHz for 5254B).
MIXING FREQUENCIES: 0. 15 to 3 GHz in 50 MHz steps (0. 2 to 3GHz Tor 5254B).
INPUT VOLTAGE RANGE: 50 mV (-13 dBm) to 1V(+13 dBm) (min. to max. rms).
MAXIMUM INPUT OVERLOAD: 2. 2V rms (+20 dBm) 125 Vdc.
NOMINAL INPUT IMPEDANCE: 50 ohms.
INPUT COUPLING: AC.
RESOLUTION: 1Hz in 1sec. ,10 Hz in 0. 1sec. ,etc.
ACCURACY: Maintains counter accuracy.
REGISTRATION: Counter display in MHz is added to converter dial reading.
LEVEL INDICATOR: Meter aids frequency selection and indicates usable signal level
AUXILIARY OUTPUT: 1to 50 MHz on front panel.
INPUT CONNECTOR: Type Nfemale.
WEIGHT: Net, 5lbs (2,3 kg). Shipping, 1lbs (3,2 kg).
1-1/1-2

Model 5254C Section II
SECTION II
INSTALLATION
2-1. INTRODUCTION.
2-2. This section contains information on unpacking,
inspection, repacking, storage, and installation.
2-3. UNPACKING AND INSPECTION.
2-4. If the shipping carton is damaged, ask that the
carrier's agent be present when the instrument is un-
packed. Inspect the instrument for damage (scratches,
dents, broken knobs, etc.). If the instrument is
damaged or fails to meet specifications (Performance
Check, Table 5-4), notify the carrier and the nearest
Hewlett-Packard sales and service office immediately
(offices are listed at the back of this manual). Retain
the shipping carton and the padding material for the
carrier’s inspection. The sales and service office
will arrange for the repair or replacement of your in-
strument without waiting for the claim against the car-
rier to be settled.
2-5. STORAGE AND SHIPMENT.
2-6. PACKAGING. To protect your instrument dur-
ing shipment or storage, use the best packaging
methods available. Your Hewlett-Packard sales and
service office can provide materials similar to those
used for original factory packaging. Contract pack-
aging companies can provide dependable custom pack-
aging on short notice.
a. If possible, use the original container designed
for the instrument. Otherwise, use astrong carton
(350 Ib/sq inch bursting strength) or wooden box to
house the instrument.
b. Wrap the instrument in heavy paper or plastic
before placing it in the shipping container.
c. Use plenty of packing material around all sides
of the instrument and protect the front panel with card-
board strips.
d. Seal the package with strong tape or metal bands.
Mark with "Delicate Instrument. "
e. Refer to the address list at the rear of this man-
ual and check with your Hewlett-Packard sales and
service office for shipping instructions. All corres-
pondence should refer to an instrument by Model num-
ber and the full eight-digit serial number.
2-7. ENVIRONMENT. Conditions during storage and
shipment should normally be limited as follows:
a. Maximum temperature 167° F(75°C).
b. Minimum temperature -40° F(-40°C).
CAUTION
TURN COUNTER POWER OFF BEFORE IN-
STALLING OR REMOVING FREQUENCY
CONVERTER.
2-8. INSTALLATION.
2-9. The Model 5254C plugs into the rectangular
compartment at the right-hand side of the front panel
of an HP Electronic Counter. To install unit in coun-
ter, first check that counter’s retaining latch is turned
fully counterclockwise, then push unit firmly into com-
partment until front panel of plug-in is flush with front
panel of counter. Then turn retaining latch clockwise
until it is tight.
2-10. To remove unit from counter, turn retaining
latch counterclockwise to its stop. Then grasp mixing
frequency selector and firmly pull unit from counter.
If any difficulty is encountered with installation or re-
moval, check that retaining latch is fully counterclock-
wise.
2-11. POWER REQUIREMENTS.
2-12. All electrical power required to operate the
Model 5254C is supplied by the counter in which the
unit is installed.
2-13. ELECTRICAL CONNECTIONS.
2-14. The two INPUT connectors on the front panel
of plug-in (see Figure 3-1) are the only external elec-
trical connections to the unit. All other connections
are made through the 50-pin connector at the rear of
the plug-in when installed in the counter.

Model 5254C Section III
SECTION III
OPERATION
3-1. INTRODUCTION.
3-2. The Model 5254C Frequency Converter increases
the range of an HP Electronic Counter to. 15 through
3. 0GHz (150 through 3000 MHz). As ageneral rule
to measure frequency, always start with the Mixing
Frequency Control below .2GHz and tune upward in
frequency to obtain first response and tune for a
maximum reading in the green portion of the meter
scale. The input frequency is the sum of the counter
reading and the dial frequency reading. This proce-
dure will be valid whether there are responses in 1,
2, or 3consecutive harmonic reference frequencies;
see Figure 3-1. If the input signal level to the con-
verter is high, the second, third and other harmonics
of this signal may be generated. Therefore, tuning
Mixing Frequency Control from the low end upward
will enable the input fundamental frequency to be de-
tected before its harmonics. In the 5254C, harmonics
of the reference-frequency signals are held to such a
low level that regardless of input signal level, their
mixing effects are not observable, avoiding possible
ambiguity. Figure 3-1 provides astep-by-step pro-
cedure to be used for measurement of frequencies from
.15 to 3. 0GHz (150 MHz to 3000 MHz). The only ex-
ception is if the first response occurs at •15 GHz or
.25 GHz. To avoid possible ambiguity in these cases,
start from above .45 GHz and tune downward in fre-
quency for the first response and subtract the counter
reading from the dial frequency for the frequency of
the input signal.
Note
If the input frequency is known approximately,
the Mixing Frequency Control can be set a
hundred megahertz below the input signal. Tune
up for the first response and add the counter
reading to the dial frequency.
3-3. CONTROLS AND INPUT.
3-4. GENERAL. The function of the front panel con-
trol, meter, connectors, and retaining screws are
discussed in Paragraphs 3-5 through 3-8.
3-5. INPUT CONNECTOR. Signal input, 50 ohms in-
put impedance, 50 mV (-13 dBm in 50 ohms) to 1V
rms (+13 dBm in 50 ohms) into Type Nfemale
connector.
3-6. MIXING FREQUENCY SELECTOR. Calibrated
from .2to 3. 0GHz (200 MHz to 3000 MHz), this con-
trol tunes the internal cavity to select aharmonic of
50 MHz to be heterodyned with the INPUT signal.
3-7. LEVEL INDICATOR METER. The meter circuit
continuously monitors the level of the difference fre-
quency output of the converter to the counter. When
meter reads in the green portion of its scale, INPUT
signal amplitude is adequate for accurate frequency
measurement.
3-8. AUX OUT CONNECTOR. The 1MHz to 50 MHz
video amplifier output appears at AUX OUT BNC type
connector.
3-9. MAXIMUM INPUT VOLTAGES.
3-10. Damage to the converter may result if an ac
signal greater than +20 dBm in 50 ohms (2.2 Vrms)
or adc voltage greater than 100V is applied to the
converter INPUT connector.
3-11. FREQUENCY MEASUREMENT WITH
AMPLITUDE LESS THAN 50 MV RMS.
3-12. The front panel level indicator meter indicates
in the green portion of its scale only when converter
Table 3-1. Frequency Resolution
INPUT SIGNAL FREQUENCY =2.4911223344 GHz
MIXING FREQUENCY CONTROL set to 2. 45 GHz
Time Base
Setting Counter Display Measurement Resolution
.1 jl s*(no display)
1/IS 41.MHz 2. 491GHz
10 /is 4.11 MHz 2. 491 1 GHz
.1ms 41.1 2MHz 2. 49112 GHz
1ms 41122 kHz 2. 491122GHz
10 ms 41 1 22.3 kHz 2.4 911223GHz
.1s41122.3 3kHz 2. 491 1 2 2 33GHz
1s41122. 334kHz 2. 491 122334 GHz
10 s1 1 22.3 344kHz 2.491 1223344 GHz
3-1

Section III Model 5254C
is properly tuned and amplitude of INPUT signal is
adequate for accurate frequency measurement.
NOTE
Only when the level indicator
meter is in the green zone will
the display count be valid.
3-13. DOUBLE CHECKING FREQUENCY
MEASUREMENT RESULT.
3-14. Because of the heterodyne action of the con-
verter, frequency measurement results obtained at
any one setting of the Mixing Frequency Control may
be checked at other settings. In most cases these
will be two consecutive responses: tune in the first
response and add the counter display to the dial fre-
quency reading; then tune up in frequency to the sec-
ond response and subtract the counter display from
the dial frequency reading (see Table 3-2). In some
cases there will be three consecutive responses (see
Figure 3-1); in these cases the third response will be
the one in which you subtract the counter display from
the dial frequency reading.
3-15. Acounter reading will only be obtained if the
difference frequency between the MIXING FREQUENCY
and the INPUT frequency is more than 1MHz and less
than 53 MHz (the bandwidth of the Video Amplifier As-
sembly A5).
3-16. AID TO RAPID TUNING.
3-17. When using a counter with MANUAL START it
is easy to obtain an indication of the proper MIXING
FREQUENCY when rapidly tuning the Model 5254C
through its frequency range in search of an unknown
INPUT frequency. Set FUNCTION control to MANUAL
START. This allows the counter to totalize each cycle
of any difference frequency produced during rapid
tuning. When the counter display changes, indicating
that the MIXING FREQUENCY is heterodyning with the
INPUT frequency and producing adifference frequency
within the frequency range of the basic counter, set
counter FUNCTION control to FREQUENCY and pro-
ceed with measurement.
Table 3-2. Typical Double -Check Frequency Measurement
Input Frequency Counter Reading* Mixing Frequency Meter Indication Response
First Response:
34567. 8kHz 1.2 GHz Peak 1.2000000 GHz
+345678 kHz
1.2345678 GHz
1.2345678 GHz Second Response:
15432. 2kHz 1.25 GHz Peak 1. 2500000 GHz
-154322 kHz
1.2345678 GHz
*Counter in 10 ms Gate to give reading in kHz.
3-2

Model 5254C Section III
f7^T] 5254C FREQUENCY CONVERTER .15-3.0 GHz
LkCZJ HEWLETT •PACKARD
1. Refer to the Operating Section of your HP Electronic Counter Operating manual
for counter settings as well as installation instructions when using the HP 5254C
plug-in.
2. Connect signal whose frequency is to be measured to HP 5254C INPUT.
3. Set Mixing Frequency Control to read slightly less than 0. 2GHz.
4. Slowly turn Mixing Frequency Control counterclockwise to obtain first response,
and tune for amaximum reading in the green portion of the Level Indicator Meter
scale. (See below for examples of 1, 2, and 3responses.
)
5. Add counter display in (kHz) to Mixing Frequency Control reading (GHz) for fre-
quency of INPUT signal.
Input Freq Display Meter Dial Response
EXAMPLE OF ONE RESPONSE
3020 MHz 000000.00 MHz Red 2. 95 GHz (2950 MHz) No response, difference frequency greater
than 1MHz to 53 MHz pass band of video ampl.
000020. 00 MHz Green 3. 0GHz (3000 MHz) First response 3000 MHz +20 MHz =3020 MHz
EXAMPLES OF TWO RESPONSES
1020 MHz 000020. 00 MHz Green 1. 0GHz (1000 MHz) First response 1000 MHz+ 20 MHz =1020 MHz
000030. 00 MHz Green 1. 05 GHz (1050 MHz) Second response 1050 MHz -30 MHz =1020 MHz
000050.00 MHz Green .85 GHz (850 MHz) First response 850 MHz +50 MHz =900 MHz
900 MHz 000000. 00 MHz Red .90 GHz (900 MHz) No response, difference frequency less than
1MHz to 53 MHz pass band of video amplifier
000050. 00 MHz Green .95 GHz (950 MHz) Second response 950 MHz -50 MHz =900 MHz
EXAMPLE OF THREE RESPONSES
000051. 00 MHz Green .8GHz (800 MHz) First response 800 MHz +51 MHz =851 MHz
851 MHz 000001. 00 MHz Green .85 GHz (850 MHz) Second response 850 MHz +1MHz =851 MHz
000049. 00 MHz Green .9GHz (900 MHz) Third response 900 MHz -49 MHz =851 MHz
*Counter in .1ms Gate to give reading in Megahertz in all examples.
Figure 3-1. Model 5254C Operating Procedure
3-3/3-4

Model 5254C Section IV
SECTION IV
PRINCIPLES OF OPERATION
4-1. GENERAL.
4-2, The Model 5254C is aheterodyne frequency con-
verter designed to extend the range of frequency meas-
urement of an Electronic Counter to ,15 GHz through
3GHz (150 MHz through 3000 MHz).
output of the video amplifier is monitored by ameter
circuit which indicates when difference frequency out-
put amplitude is greater than the minimum signal re-
quired by the counter input circuit.
Note
4-3. The Converter contains five basic functional
sections: multiplier amplifier, harmonic generator
and harmonic selector cavity, mixer, filter, and video
amplifier. (See Figure 4-1, and for circuit details re-
fer to the schematic diagrams, Figures 8-2 and 8-3.
)
10 MHz
SIGNAL
FROM
COUNTER
DIFFERENCE
FREQUENCY
AUX TO
OUT COUNTER
Figure 4-1. Model 5254C Block Diagram
4-4. In normal operation the harmonic generator pro-
duces all of the harmonics of 50 MHz between 150 MHz
and 3000 MHz. The harmonic selector cavity is tuned
to select one of these harmonics to be supplied through
the low-pass filter to the mixer. The mixer output is
the difference frequency produced by mixing of the in-
put frequency and the frequency supplied by the harm-
onic selector cavity. This difference frequency is amp-
lified by the video amplifier and supplied to the counter
input circuit. Alow-pass filter within the video amp-
lifier prevents difference frequency signals above 53
MHz from reaching the counter input circuit. The
In the following discussion complete reference
designations are used to identify components.
This is to prevent confusion between reference
designations of components located on the chas-
sis and components located on an assembly.
For example, "RF* would refer to acomponent
located on the chassis, while "A1R1” would re-
fer to acomponent located on the multiplier
amplifier assembly A1 (see Table 5-2 for as-
sembly designations).
4-5. MULTIPLIER AMPLIFIER Al.
(see Figure 4-2).
4-6. A10-megahertz signal from the counter is ap-
plied to buffer amplifier A1Q1. The buffer amplifier
A1Q1 is atuned amplifier providing aconstant ampli-
tude 10 MHz signal to the multiplier A1Q2, and pro-
vides isolation of converter from counter. The x5
multiplier A1Q2 is atuned class Camplifier with the
input tuned to 10 MHz and the resonant output tuned
to the fifth multiple of the input signal providing a50
MHz output signal. The output of the multiplier is
amplified by A1Q3 and applied to the crystal filter.
The half lattice crystal filter (AlYl and A1C13) is a
50 megahertz band-bass filter. A1C13 is used to bal-
ance out crystal capacitance. Aseries of tuned power
amplifiers A1Q4, A1Q5, and A1Q6 amplify the signal
from the crystal filter to drive the harmonic generator.
4-7. HARMONIC GENERATOR A2 AND
HARMONIC SELECTOR CAVITY.
(See Figure 4-2).
4-8. The harmonic generator consists of a50-MHz
tuned circuit, driving the step recovery diode, A2CR1.
The step recovery diode takes energy from the tuned
circuit during aportion of each cycle of the 50 MHz
oscillation and produces asharp step in the current
flowing through the diode. The diode forms aloop in-
put coupling to the harmonic selector cavity and the
step in the current through the diode makes available,
inside the cavity, the harmonics of 50 MHz from 150
MHz (third harmonic) to 3000 MHz (sixtieth harmonic).
The probe tunes the cavity to select the desired har-
monic and provides coupling from the harmonic selec-
tor cavity through the filter assembly A4 to one of the
two inputs of the mixer assembly A3.
4-9. FILTER ASSEMBLY A4. (See Figure 4-3)
4-10. The output signal of the harmonic selector
cavity is applied to aTschebyscheff low -pass filter
(A4), with acut-off frequency of 3GHz, to limit
4-1

Section IV Model 5254C
selected mixing frequency. The filter has a50-ohm
termination at both the input and output. The output
signal from the filter (A4) is applied to one of the in-
puts of the mixer assembly (A3).
4-11. MIXER ASSEMBLY A3. (See Figure 4-3).
4-12. The mixer assembly uses two diodes in abal-
anced mixer circuit in order to minimize the genera-
tion of even order harmonics of both the input signal
and the selected mixing frequency. The combination
of the terminating resistor A3R1 and the shunting ef-
fect of the diodes gives an input impedance of 50 ohms
and provides alow standing wave ratio (typically be-
low 1. 5up to 3. 0GHz. Capacitor A3C1 provides dc
isolation up to 100 volts. A5R1, A5R2, and A5R3
control the bias currents of the mixer diodes (A3CR1
and A3CR2) and are adjusted for maximum common
mode rejectionwithinthe video band (1 MHz to 53 MHz).
The non-linearity of the diodes (A3CR1 and A3CR2)
gives rise to signals with frequencies which are the
sum and difference of the two mixing frequencies
Figure 4-2. Multiplier Amplifier Assembly Al, Harmonic Generator Assembly A2,
and Harmonic Selector Cavity, Block Diagram (5254C)
INPUT SIG Jl
Y
MIXING FREQ
FROM HAR
SELECTOR
CAVITY
Figure 4-3. Low-Pass Filter Assembly A4, Mixer Assembly A3, and
Video Amplifier Assembly A5, Block Diagram (5254C)
4-2

Model 5254C Section IV
INPUT frequency and selected mixing frequency). The
difference frequency signal in particular is coupled to
the input of the differential amplifier (A5Q1 and A5Q2)
through coupling resistors (A3R3 and A3R4) as adif-
ferential signal.
4-13. VIDEO AMPLIFIER A5. (See Figure 4-3)
4-14. The two signals from mixer A3 are applied to
the bases of differential amplifier A5Q1 and A5Q2.
A5Q1 and A5Q2 output is applied to the second stage
of differential amplification (A5Q3 and A5Q4). A5Q3
collector output goes to ground through A5C4 and
A5C5, and A5Q4 collector output is applied to the
base of A5Q5. A5Q5 and A5Q6 form afeedback amp-
lifier with aconstant gain of 10. A5Q7 and A5Q8 limit
the signal and provide ahigh impedance athe collector
of A5Q8. This high impedance is shunted with 100
ohms (A5R24) to provide the input impedance required
by the low-pass filter. The low-pass filter, athree
-
section Tschebycheff filter, provides a53-MHz cut-
off frequency for the video amplifier. A5Q9 andA5Q10
form ashunt feedback amplifier providing alow im-
pedance input at the base of A5Q9. This, in series
with 91 -ohm resistor A5R25 provides 100 ohms out-
put impedance required by the low-pass filter. A5Q11
is abuffer amplifier with aresistive divider output
providing the auxiliary output to Jl. A5Q11 output
also goes to trigger circuit A5Q13, A5Q14, and A5Q15.
Tunnel diode A5CR3 shapes the signal into arectangu-
lar pulse with very fast rise and fall times. This sig-
nal causes the trigger transistors A5Q14 and A5Q15
to switch quickly. With AUX OUT jack Jl terminated
in 50 ohms, output to the counter is twice as large as
the auxiliary output. There is sufficient isolation in
the divider network to prevent the signal to the coun-
ter from being affected by termination at the auxiliary
output.
4-3

Section VModel 5254C
Table 5-1. Recommended Test Equipment
Instrument Required
Characteristics Use Instrument
Recommended
Electronic Counter Supply Power, supplies
10 MHz signal
Operational Indicator
if Model 5245L
VHF Signal
Generator 200 MHz to 480 MHz
10 mV to .1VPerformance Check
Circuit Adjustment if Model 608E
UHF Signal
Generator 450 MHz to 1230 MHz
10 mV to .1VPerformance Check if Model 612A
UHF Signal
Generator 800 MHz to 2400 MHz
10 mV to .1VPerformance Check if. Model 614A
or 8614A
UHF Signal
Generator 1.8 GHz to 4.5 GHz
10 mV to .1VPerformance Check if Model 616B
or 8616A
DC VTVM and
Ohmmeter 0to -i and -25 Vdc
.1Vresolution
0to 100 Mohms
Circuit Adjustment
Troubleshooting
if Model 412
A
RF Millivoltmeter 1MHz to 20 MHz
10 mV to 10 Vrms
10 mV resolution
Circuit Adjustment if Model 411A
if. 11 02 5AProbe
Oscilloscope 1000 MHz bandwidtli Circuit Adjustment
Troubleshooting 'If; Model 140A with
141 1A Plug-in; 1425A
Plug-in &143 0A Sampler
Termination 50 ohms feedthrough Circuit Adjustment
R X Meter 60 MHz to 120 MHz Circuit Adjustment Boonton 250A
Spectrum Analyzer 3GHz Frequency Circuit Adjustment if 85 IB &8551B
Male BNC Plug
Connector Circuit Adjustment if 1250-0052
BNC male to type N
female adapter
Circuit Adjustment if 1250-0077
Extension Cable 50 pin straight -thru Circuit Adjustment if 10506B
Oscillator
Synchronizer Performance Check DY 2654A
Quartz Oscillator 1MHz Performance Check •if 106A/B
Frequency
Synthesizer 0-500 MHz
0dBm level
Performance Check if 5105A/5110B
Frequency
Sample Cable Optional with
DY 2654A Performance Check if 5060-2597
Frequency
Control Cable Optional with
DY 2654A Performance Check if 5060-2598
5-0

Model 5254C Section V
SECTION V
MAINTENANCE
5-1. INTRODUCTION.
5-2. This section provides maintenance and service
information for the Model 5254C Frequency Converter.
Included are aperiodic maintenance procedure, a
table of recommended test equipment, an in-cabinet
performance check which may be used to verify proper
operation of the frequency converter, troubleshooting
procedure, and repair and adjustment procedure.
5-3. PERIODIC MAINTENANCE.
5-4. No special maintenance procedures are required
when the converter is operated in normal environments.
However, if unit is subjected to operation in extremely
dusty environments, periodically clean all gears with
alint-free cloth and apply a coating of light, petroleum
base, open-gear grease to all gear teeth.
5-5. TEST EQUIPMENT.
5-6. Recommended test equipment for performance
checking, troubleshooting and circuit adjustment after
repair is listed in Table 5-1. Other test instruments
may be used if their specifications equal or exceed
the required characteristics.
5-7. IN-CABINET PERFORMANCE CHECK.
5-8. The following performance check (Table 5-4)
verifies proper operation of all circuits in the Model
5254C and may be used:
a. as part of an incoming inspection check of instru-
ment specifications;
b. periodically, for instruments used in systems
where maximum reliability is of utmost importance;
c. as part of atroubleshooting procedure to locate
malfunctioning circuits, and
d. after any repairs or adjustments, before return-
ing instrument to regular service.
5-9. TROUBLESHOOTING.
5-10. Refer to Section IV, Principles of Operation,
for information on the operation of circuits. Table 5-2
gives the reference designations of assemblies used
in the converter and their corresponding nomenclatures.
Figure 5-2 shows the location of all assemblies used
in the Model 5254C. Figures 8-2 and 8-3 show com-
ponent location on the assemblies. Table 8-1, Trouble-
shooting Aids, gives information on waveforms and
dc voltages which are present when circuits are oper-
ating properly. The waveforms are referenced to test
points throughout the converter. These test points
are keyed to the schematic diagrams, Figures 8-2
and 8-3. Table 5-2. Assembly Designations
A1 MULTIPLIER AMPLIFIER
A2HARMONIC GENERATOR
A3 MIXER
A4 LOW PASS FILTER
A5 VIDEO AMPLIFIER
5-11. MULTIPLIER AMPLIFIER ASSEMBLY Al.
5-12. If the Multiplier Amplifier Assembly is sus-
pected of being faulty, use the test points on the sche-
matic diagram, Figure 8-2, and the test points and
dc voltages given in Troubleshooting Aids, Table 8-1,
in the following order 7, 1, 2, 3, 4, 5, and 6to help
isolate the faulty circuit.
5-13. MIXER ASSEMBLY A3,
5-14. Afaulty mixer assembly is usually indicated
by poor sensitivity, noisy signal output from the video
amplifier. If the mixer assembly is suspected of being
faulty, remove amplifier side plate (MP12), see Fig-
ure 5-2, and perform the resistance check given in
Table 5-3.
Table 5-3. Mixer Resistance Check
—
Check Connect Ohmmeter (fy 41 2Aonly) Ohmmeter
Scale Reading
Ohms Lead Common Lead
iA3R3 Ground XI
K
Greater than 10K ohms
2Ground A3R3 X1K 600 -1200 ohms
3A3R4 Ground XI
K
600 -1200 ohms
4Ground A3R4 X1K Greater than 10K ohms
Note: These measurements can be made with the Mixer Assembly installed in the instrument and
without unsoldering any wires.
5-1

Section VModel 5254C
a. If any reading for checks 1thru 4is 500 ohms,
there is ashort circuit in the mixer.
b. If checks 1or 4read less than 10K the diodes
are defective.
c. If "infinity" is read there is an open circuit.
5-15. VIDEO AMPLIFIER ASSEMBLY A5.
5-16. Afaulty video amplifier circuit can usually be
detected by one simple check; short either input, base
of A5Q1 or A5Q2 to ground and the amplifier should
oscillate causing an increased level indicator meter
reading. If it does not it may be presumed faulty.
Use the test points in the schematic diagram, Figure
8-6 and the test points and dc voltages given in
Troubleshooting Aids, Table 5-4.
5-17. REPAIR AND REPLACEMENT.
5-18. GENERAL.
5-19. Paragraphs 5-20 through 5-35 are replacement
procedures to aid repair. No attempt should be made
to repair: 1) the Harmonic Generator A2; 2) the Har-
monic Selector Cavity; 3) the Mixer Assembly A3, or
4) the Filter Assembly A4. These assemblies should
be replaced as a unit. For assistance contact your
Hewlett-Packard sales and service office.
5-20. PRINTED CIRCUIT COMPONENT
REPLACEMENT.
5-21. Component lead holes in the Model 5254C cir-
cuit boards have plated walls to ensure good electrical
contact between conductors on the opposite sides of
the board. To prevent damage to this plating and to
the replacement component, apply heat sparingly and
work carefully. The following replacement procedure
is recommended:
a. Remove defective component.
b. Melt solder in component lead holes. Use clean
dry soldering iron to remove excess solder. Clean
holes with toothpick or wooden splinter. Do not use
metal tool for cleaning as this may damage through-
hole plating.
c. Bend lead of replacement component to the cor-
rect shape and insert component leads into component
lead holes. Use heat and solder sparingly, solder leads
in place. Heat may be applied to either side of board.
Aheat sink (longnose pliers, commercial heat -sink
tweezers, etc) should be used when replacing transis-
tors and diodes in order to prevent conduction of ex-
cessive heat from the soldering iron to the component.
d. Through-hole plating breaks are indicated by the
separation from the board of the round conductor pad
on either side of the board. To repair breaks, press
conductor pads against board and solder replacement
component lead to conductor pad on both sides of the
board.
5-22. MULTIPLIER AMPLIFIER ASSEMBLY A1
.
5-23. To remove the Multiplier Amplifier Assembly
A1 see Figure 5-2 and proceed as follows:
a. Unscrew the four screws which secure left side
plate (MP7) and remove left side plate.
b. Unscrew the four screws which secure top plate
(MP6) and remove top plate.
c. Disconnect the following wires from Multiplier
Amplifier Assembly A1 (see Figure 8-2 ):
From
red P6(13)
violet P6(15)
green P6(50)
red A5L14
violet A5L15
d. Disconnect black wire to meter from ground lug
on MP14, and white wire to meter from capacitor C3
and MP14.
e. Remove screw securing aluminum spacer rod
(MP10) to plug-in guide (MP9) on right side of instru-
ment. Unscrew spacer (MP10) from front panel.
f. Remove the two screws that secure amplifier
side plate (MP12) to front panel.
g. Remove the three screws that mount machined
amplifier shield (MP14) and slide shield to rear and
out the right side to clear board bracket (MP13)from
Multiplier Amplifier Assembly Al.
h. Remove the two screws which secure Multiplier
Amplifier Assembly to Harmonic Selector Cavity and
remove assembly. Note: Harmonic Generator As-
sembly A2 is mounted to bottom of this assembly.
i. To replace this assembly, reverse the procedure
used in steps athrough h.
j. All replacement Multiplier Amplifier Assemblies
are adjusted at the factory for optimum performance;
however, if ageneral operation check is desired, an
in-cabinet performance check is given in Table 5-4.
5-24. HARMONIC GENERATOR ASSEMBLY A2.
5-25. This assembly should be replaced as aunit
and no attempt made to repair it. To remove this
assembly see Figure 5-2 and proceed as follows:
a. Remove Multiplier Amplifier Assembly Al as
described in Paragraph 5-22.
b. Remove the two harmonic generator mounting-
screws.
c. Unsolder capacitor C25 from harmonic genera-
tor leads (see Figure 8-2).
d. Unsolder harmonic generator leads from As-
sembly Al printed circuit board and remove harmonic
generator (see Figure 8-2).
e. To replace this assembly reverse the procedure
used in steps athrough d.
5-2

Model 5254C Section V
f. The Multiplier Amplifier alignment procedure
(Paragraph 5-37) should be performed after replac-
ing Harmonic Generator Assembly.
5-26. HARMONIC SELECTOR CAVITY.
5-27. No attempt should be made to repair the Har-
monic Selector Cavity; it should be replaced as aunit.
To remove the cavity, see Figures 8-2 and 8-3 and
proceed as follows:
a. Remove Multiplier Amplifier Assembly as des-
cribed in Paragraph 5-22.
b. Remove the four screws that secure cavity plug
assembly (MP3) and remove cavity plug and cavity
output cable.
c. Unscrew knob set screws and remove knob.
d. Remove the four screws that secure mixing
frequency dial and remove dial.
e. Remove the five Harmonic Selector Cavity mount-
ing screws. Remove cavity by sliding to rear and
lifting it out through the left side.
f. To replace this assembly reverse the procedure
used in steps athrough e.
g. All replacement Harmonic Selector Cavities are
adjusted at the factory for optimum performance. How-
ever, if ageneral operation check is desired, and in-
cabinet performance check is given in Table 5-4.
5-28. MIXER ASSEMBLY A3.
5-29. No attempt should be made to repair this as-
sembly; it should be replaced as aunit. To remove
the assembly, see Figure 5-2 and proceed as follows:
a. Remove the four screws which secure top plate
(MP6) and remove top plate.
b. Disconnect black wire to meter from ground lug-
on MP14 and white wire to meter from capacitor C3
on MP14.
c. Remove screw securing aluminum spacer rod
(MP10) to plug-in guide (MP9) on right side of instru-
ment. Unscrew spacer (MP10) from front panel.
d. Remove the twelve screws that secure amplifier
side plate (MP12) and remove side plate.
e. Disconnect, orange wire from A3R4 and blue wire
from A3R3.
f. Slide machined amplifier shield to rear and out
the right side to make mixer (A3) and mixer securing
screws accessible. See Figure 8-4.
g. Remove the four mixer securing screws. Re-
move mixer by carefully pulling it out of its cavity
in MP14 (machined amplifier shield)
.
h. To replace the Mixer Assembly A3, reverse the
procedure used in steps athrough g.
i. The Mixer Balance adjustment, Paragraph 5-40,
procedure should be performed after replacing the
Mixer Assembly A3).
5-30. FILTER ASSEMBLY A4.
5-31. To remove Filter Assembly A4, see Figure 5-2
and proceed as follows:
a. Remove Mixer Assembly A3 as described in
Paragraph 5-28.
b. Pull the Filter Assembly out of its cavity in
MP14 with apair of longnose pliers.
c. To replace this assembly reverse the procedure
used in steps aand b.
5-32. VIDEO AMPLIFIER ASSEMBLY A5.
5-33. To remove Video Amplifier Assembly A5, see
Figure 5-2 and follow this procedure:
a. Remove the twelve screws that secure the amp-
lifier side plate (MP12) and remove side plate.
b. Disconnect the following wires: 1) the white wire
from capacitor C3; 2) the red wire from capacitor Cl;
3) the violet wire from capacitor C2; and 4) the two
leads from the video amplifier output cables.
c. Remove the five Video Amplifier securing screws
and remove the Video Amplifier Assembly A5.
d. To replace the Video Amplifier Assembly A5
reverse the procedure used in steps athru c.
e. The Mixer Balance Adjust control is on the
Video Amplifier Assembly. The replacement of the
Video Amplifier Assembly necessitates the adjust-
ment of the Mixer Balance in Paragraph 5-40.
f. All replacement Video Amplifier Assemblies
are adjusted at the factory for optimum performance.
However, if general operation check is desired, an
in-cabinet performance check is given in Table 5-4.
5-34. METER REPLACEMENT PROCEDURE.
5-35. To remove level indicator meter, see Figure
5-2 and proceed as follows:
a. Remove the four screws that secure the top
plate (MP6) and remove the top plate.
b. Remove the four screws that secure the side
plate (MP7) and remove the side plate.
c. Remove the three screws securing the three
aluminum spacer rods (MP10).
d. Unscrew the knob set screws and remove the
knob.
5-3

Section VModel 5254C
e. Remove the four screws that secure the mixing
frequency dial and remove dial.
f. Remove the two screws that secure front panel
to bottom plate (MP8).
g. Cut connecting wires at meter terminals.
h. Remove panel from instrument to permit access
to meter.
i. Remove the two screws from meter bezel at sides
of meter. Push bezel forward as far as possible.
j. Grasp meter and gently pull (with bracket MP5)
backwards out of front panel hole.
k. Remove meter bracket (MP5) and hardware from
meter and install in identical manner on replacement
meter.
l. Replace meter (with bracket) in unit by reversing
procedure used in steps athrough k. Strip 1/4 inch
insulation from ends of each connecting wire and solder
to meter terminals. White wire goes to inside term-
inal; black wire goes to outside terminal.
5-36. CIRCUIT ADJUSTMENTS.
5-37. MULTIPLIER AMPLIFIER ALIGNMENT PRO-
CEDURE. Two procedures are given for multiplier
amplifier alignment; Procedure ais to be used if the
multiplier is working and just requires peaking, and
Procedure bif the multiplier has no output (checkout-
put by measuring dc voltage at junction of C25 and
R16; normal reading is 2volts or more).
a. 1) With counter power off, connect converter to
counter with Extension Cable HP 10506 B.
2) Remove four screws which secure MP6 (top
plate) and remove MP6.
3) Set UHF Signal Generator to any frequency
between 2and 3GHz at 50 mV and connect to
converter INPUT.
4) Turn counter power on and set controls as
shown in Figure 3-1. Tune converter for a
maximum indication on Level Indicator Meter.
5) Adjust UHF Signal Generator output level for
areading on the red/ green line of the con-
verter Level Indicator Meter.
NOTE: If counter displays adifference fre-
quency below 1MHz, adjust UHF Signal slightly
so counter display is between 1to 50 MHz.
6) Adjust A1L2, A1L3, A1L5, A1L6, A1L8,
A1L10 and A1C25 for amaximum indication
on Level Indicator Meter.
NOTE :If the Level Indicator Meter reading
increases to above 1/2 of full scale, readjust
the UHF Signal Generator to keep indication
near the red/' green line.
7) Potentiometer A1R17 needs no adjusting pro-
viding input sensitivity is between 25 mV and
50 mV throughout the input frequency range.
8) Replace MP6 (top plate).
b. 1) With counter power off, connect converter to
counter with Extension Cable HP 10506B.
2) Remove four screws which secure MP6 (top
plate) and remove MP6.
3) Turn counter power on.
4) Connect HP 140Awith HP 14 10Aplug in (1000
MHz Oscilloscope), using an HP 10214A
Divider and an HP 102 17A Blocking Capacitoi
to collector of A1Q1. Set Oscilloscope vert-
ical gain for 5V/cm(with 10:1 Divider set to
.5V/cm) and horizontal to .05 /is/ cm, and
trigger oscilloscope from counter OUTPUT
STD FREQ 10 MHz (rear of counter).
5) Observe waveform and tune A1L2 for maxi-
mum. Waveform and amplitude should ap-
proximate that in test point 2, Table 8-1.
6) Connect oscilloscope probe to the collector
of A1Q2. Set oscilloscope Vertical to 2V/cm.
7) Observe waveform and adjust A1 L3 for maxi-
mum;then adjust A1L5 for maximum. Wave-
form and amplitude should approximate that
in test point 3, Table 8-1.
8) Connect oscilloscope probe to collector of
A1Q3.
9) Observe waveform and adjust A1L6 for the
approximate waveform and amplitude shown
in test point 4, Table 8-1.
10) Connect oscilloscope probe to collector of
A1Q4. Set oscilloscope Vertical to 1V/cm.
11) Observe waveform and adjust A1L8 for max-
imum. Waveform and amplitude should ap-
proximate that shown in test point 5, Table
8-1.
12) Connect oscilloscope probe to collector of
A1Q5. Set oscilloscope Vertical to 2V/cm.
13) Observe waveform and adjust A1 LI 0for max-
imum. Waveform and amplitude should ap-
proximate that shown in test point 6, Table
8-1.
14) Connect oscilloscope probe to collector of
A1Q6. Set oscilloscope Vertical to 10V/cm.
15) Observe waveform and tune A1C25 for max-
imum. Note two maxima should be noted as
the capacitor is turned through 360°. Wave-
form and amplitude should now approximate
that in test point 7, Table 8-1. The output
should be asine wave of 50 Me, approximately
20 volts amplitude; if not proceed to steps 16
through 19 and then repeat step 15.
16) Adjust capacitor A1C25 to the centei of its
range (notch perpendicular to axis of leads).
17) Unsolder from the board the end of A1L12 at
its junction with A1L11 and A1C23.
18) Observe the waveform and tune A1L12 for a
maximum by increasing or reducing the loop
diameter. Resolder A1L12 to the board.
19) See Para. 5-37 afor final peaking adjustment.
5-4

Model 5254C Section V
5-38. CRYSTAL FILTER ADJUSTMENT.
5-39. To adjust the cyrstal bandpass filter in the
Multiplier Amplifier Assembly Al, proceed as
follows:
a. With counter power off, connect converter to
counter with Extension Cable HP 10506B.
b. Remove the four screws which secure MP6 (top
plate) and remove MP6.
c. Remove the four screws which secure MP7 (left
side plate) and remove MP7.
d. Remove Cavity Output Cable Assembly from
MP14 (Machined Amplifier Shield). To prevent
damage to the cable assembly, first remove the four
screws that secure the Cavity Plug Assembly (MP3)
and remove the cavity plug and output cable, then un-
screw and remove the other end of the output cable
from MP14 .Replace the cavity plug (MP3) and the
four screws that secure it to the cavity.
e. Connect amale BNC Plug connector (HP Stock
No. 1250-0052) to the end of the cavity output cable.
f. Using BNC male to Type Nfemale adapter (HP
Stock No. 1250-0077), connect the output cable from
Harmonic Selector Cavity to the HP Spectrum
Analyzer.
g.
Set Spectrum Analyzer Controls as follows:
VERTICAL DISPLAY
IF BANDWIDTH ..
SWEEP TIME .. .
IF GAIN
SPECTRUM WIDTH
SYNC
FREQUENCY. ...
ATTENUATOR ... .
SIGNAL IDENTIFIER
LOG
1kHz
30 ms per cm
60 dB
100 kc per cm
INT
...2-10 GHz
0dB
OFF
h. Turn counter power ON and turn Converter Mix-
ing Frequency control to 2. 95 GHz.
Figure 5-1. Spectrum Analyzer Display
c. Set 608E Signal Generator to 50 MHz at 30 mV
rms and connect to INPUT of converter.
d. Turn counter power ON and adjust Mixer Bal-
ance Adjust A5R3 for aminimum reading on the level
indicator meter.
5-41. LOW PASS FILTER ADJUSTMENT.
5-42. The Low Pass Filter in the Video Amplifier
Assembly A5 consists of three resonant LC parallel
circuits (see schematic diagram, Figure 8-6). These
circuits are pre -tuned and sealed at the factory, and
should need no further adjustment. The following
procedure can be used to verify correct operation of
the filter circuits (A5L1, A5L2, and A5L3) and to
check the tuning of replacement circuits.
a. Remove circuits (A5L1, A5L2, andA5L3)from
the Video Amplifier Assembly board.
b. Install clips on terminals of RX Meter. Clamp
one leg of the circuit under test with the clip from
the LO side. Bring other leg close to but not touch-
ing the clip on HI side.
i. Tune Spectrum Analyzer until the converter sig-
nal is found.
j.
Observe 100 kHz sideband and adjust capacitor
(A1C13) for minimum side bands (see Figure 5-1).
Side bands should be 30 dB below 2.95 GHz reference.
5-40. MIXER BALANCE ADJUSTMENT.
a. With counter power off, connect converter to
counter with Extension Cable HP 10506B.
b. Remove the twelve screws which secure MP12
(amplifier side plate) and remove .
c. Depending on which circuit is under test, the
frequency should be set to the following:
A5L1 117. 3MHz
A5L2 71.9 MHz
A5L3 63.2 MHz
d. Tune in instrument with "Detector tuning adjust-
ments” and maximize response, with and Cpset
to arbitrary values.
e. Set Rp to "infinity" and Cp to zero.
f. Null the response with the Zero Balance adjust-
ments.
g. Clamp the other leg to the HI side clip.
h. Leave Cp at zero; alternately tune the circuit
with tuning wand and adjust Rp dial until anull is
obtained.
5-5