Tektronix 7K11 User manual

.... ,
....
Tektronix, Inc.
P.O. Box
500
Beaverton, Oregon 97005
070-'664-00
TEKTRONI»
7K 11
CATV
PREAMPLIFIER
INSTRUCTION MANUAL

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WARRANTY
All TEKTRONIX instruments are w arranted against
defecti ve materials and workmansh ip for one year. Any
questions with respect to the warranty should be tak en up
with your TEKTRONIX Field Engineer or representative.
All requests for repair and replacement parts !houk:! be
directed to the TEKTRONIX Field Office or representative
in your area. This will assure you the fastest possibl
service. Please include the instrument Type Number or Part
Number and Serial Number with all requests for parts or
service.
Specifications
and price change privileges reserved.
Copyrtght @1973 by Tektronix, Inc., Beaverton, Oregon.
Printed in the United States of America. All rights reserved.
Contents of this publication may not be reproduced in any
form without permission of Tektronix, Inc.
U.S.A. and Foreign TEKTRONIX products covered by U.S.
and foreign patents and/or patents pending.
TEKTRONIX is a registered trademark of Tektronix, Inc.
•
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7K11
TABLE OF CONTENTS
SECTION 1 SPECIFICATIONS
Page
Introduction
1-1
Electrical Characteristics
1-1
SECTION 2 OPERATING INSTRUCTIONS
Introduction
2-1
Function of the Front Panel Controls and Connectors
2-1
General Operating Information
2-1
Applications 2-3
SECTION 3 PERFORMANCE CHECK
Introduction
3-1
Operational Check
3-1
Performance Verification of Specified Characteristics 3-3
Equipment Required 3-3
Check Calibrator Frequency and Output 3-4
Check Frequency Range and Display Flatness 3-4
Check Intermodulation Distortion 3-4
SECTION 4 SERVICE INSTRUCTIONS
Introduction
4-1
Circuit Description
4-1
Calibration
4-1
Maintenance 4-2
Preventive 4-2
Corrective 4-4
Obtaining Replacement Parts 4-5
Soldering Technique 4-5
Replacing Assemblies and Components 4-5
SECTION 5 OPTIONS
AND MODIFICATIONS
SECTION 6
ELECTRICAL PARTS LIST
SECTION 7
DIAGRAMS
SECTION 8
MECHANICAL PARTS LIST AND ACCESSORIES.
CHANGE
INFORMATION
®

.. ..... '
Fig. 1- 1_ 7Kll CATV Preamplifier.
7K11
COl
$cllm b, Olltsollrce-OptiotlS ->

Section 1-7K11 .
SPECIFICATIONS
Introduction
This manual contains information relative to the oper-
ation and service of the 7K11 CATV preamplifier. The
manual is divided into sections with appropriate titles. The
Table of Contents that precedes this section gives a
breakdown
of each section.
The 7K11 Preamplifier is a 7000-Series Plug-In Unit that
is designed to operate as an accessory for the 7L12 or 7L 13
Spectrum Analyzers. This unit, in combination with a
spectrum analyzer, will measure CATV system performance
as required by the FCC and compare system performance
to industry standards.
ELECTRICAL CHARACTERISTICS
(I neludes the 7L12 or 7L13)
Frequency Range
Display Flatness (7 K 11 /7L12 or 7K11 /7L 13)
Sensitivity (Signal + noise = 2X noise,
LIN mode)
Intermodulation Distortion
Reference Level
Calibrator
30 MHz to 890 MHz.
±1.0 dB, with respect to 50 MHz level, over the frequency range of
'50 MHz to 300 MHz, increasing to t2 dB with respect to 50 MHz,
over the full frequency range.
The following characteristics apply at 50 MHz in combination with
the 7L12 or 7L 13 Spectrum Analyzer.
Signal Level Resolution
Bandwidth
-90 dBmV 30 Hz
-80dBmV 300 Hz
-73dBmV
3 kHz
-65dBmV 30 kHz
-55dBmV
300 kHz
-45 dBmV 3MHz
Noise figure for the 7K11 is 5 dB or less.
1M products from two 0 dBmV input signal within any frequency
span are
down 80 dB or more. The 7K11 ~ not degrade the 1M
distortion characteristics of the Spectrum Analyzer.
Calibrated levels in 1 dB steps from +79 dBmV to 0 dBmV.
Accuracy
is referenced to the +30 dBmV Calibrator at 50 MHz.
Maximum deviation from this reference is; 0.2 dBmV + 0.01 dBmV
per dB deviation from
the +30 dBmV, 7K11 reference level. This is
equivalent to:
t [0.2 dBmV + 0.01 17K11 REF LVL - 30 dBmV11.
50 MHz to.01 % with an absolute amplitude level of +30 dBmV
±0.5 dB, from 75 n, at 25°C.
The input impedance of the 7K11 is approximately 75 n, with a VSWR of 2:1 or better with 10 dB or more attenuation
(from 50 MHz to 300 MHz).
®
1-1

Section 2-7K11
OPERATION
Introduction
This section describes the function of the front panel
controls
and connectors, a general operating procedure and
some applicationsl for the instrument. Performing the
operating procedure should help acquaint you
with the
7K11
as an accessory for the Spectrum Analyzers in CATV
applications.
FUNCTION OF THE FRONT PANEL
CONTROLS AND CONNECTORS
REFERENCE LEVEL and MAXIMUM INPUT
LEVEL
Concentric controls that select a cal ibrated reference
level for the top of the graticule on the CRT display. This
level can be selected in 1 dBmV or 10 dBmV steps to
+79 dBmV. The reference level is indicated via a readout
window on the selectors and in the upper left section of the
CRT display when the 7K11 is used with a 7000·Series
oscilloscope that has the readout feature. This REFER-
ENCE LEVEL is also the MAXIMUM INPUT signal level
for linear operation. Accuracy is referenced to the
+30
dBmV Calibrator at 50 MHz.
RF INPUT Connector
A 75 n BNC input connector for the input signal
application.
RF OUTPUT Connector
A 50 n signal source of the signal that is applied to the
RF INPUT. This signal level depends on the setting of the
REFERENCE
LEVEL selector and applied signal level. The
output is -30 dBm when the input signal level equals that
indicated by the REFERENCE LEVEL readout. NOTE:
The 7L12 or 7L13 Reference Level can be set to a setting
such as -40 dBm, to increase sensitivity, provided the
additional level (in this
case 10 dB) is summed with the
7K11 REFERENCE
LEVEL indication.
CAL OUT Connector
Provides access to an accurate +30 dBmV, 50 MHz
signal, from a 75 n source. This signal is used as an absolute
reference
for the display and is used to calibrate the
7K11/Spectrum Analyzer ensemble. Harmonics
of the 50
MHz
pilot signal provide a picket fence of markers across
the frequency span, which are used for accurate frequency
®
and span calibration. The pilot or fundamental 50 MHz
provides the amplitude REFERENCE
LEVEL. NOTE:
Always use the 75 n, 5 1/2 inch cable, which is supplied
with the accessories, to connect the CAL OUT to the RF
INPUT.
GENERAL OPERATING INFORMATION!
This portion of the section describes the front panel
adjustment procedure necessary
to calibrate the 7K11,
Spectrum Analyzer, and 7000-Series mainframe as a
system.
NOTE
External graticules are designed so they compensate
for parallax of the camera. Graticule markings will
therefore be correct on photographeddisplays.
1. Preliminary Setup and Calibration Procedure
a. Plug the 7K11 and Spectrum Analyzer into a
7000-Series mainframe.
An oscilloscope with variable per-
sistence
or bi-stable storage is recommended.
b. Connect the 7K11
and Spectrum Analyzer as shown
in Fig.
2-1 and turn the power on.
c. Set the controls and selectljlrs as shown in the
illustration. Connect the CAL OU~gnal of the 7K11 to
the RF INPUT and the RF OUTPUT to the Spectrum
Analyzer
RF Input. Ensure that the Spectrum Analyzer
Reference Level
is set to -30 d Bm and the 7K 11
REFERENCE LEVEL is +30 dBmV.
d. Allow approximately 30 to 40 minutes for the
instruments
to stabilize.
lTektronix brochure, "no loose ends", No. A·2698 (supplied with
the 7K 11 accessories); Tektronix brochure. "Spectrum Analysis and
CATV
Systems", No. A·2515; and Tektronix measurement concept
booklet, "Spectrum Analyzer Measurement Theory and Practice",
Part No. 062·1334·00; are recommended treatise 'on applications
and
measurement evaluation.
2·'

Operation-7K11
REFERENCE LEVEL
Ilnpllt Attenultionl : __ ._...,~
+30dBmV
Connect CAL OUT to
RF INPUT 15 ·1 /2 inch ---I &- -
~I .I
~~~~~~~==~~~~~~~I=::: CENTER
:: NORM
""'1- _ FREE RUN
RF OUTPUT to
RFIN
TIME / DIV : SPECTRUM
1M' 10 ms
DISPLAY MODE :
10 dB / DIV
RFATT"" ,;O dB FR'EO S""""O'V, 50 MHz
RESOLUTION : 3MHz
Fig. 2·1. Initill MIUP. showing conlrollnd se l eclor ~itions.
2-2 ®

e. Adjust the oscilloscope Intensity, Focus and Astig·
matism contlols for OPtimum display definition with
normal intensity.
f. Depress the 2 dB/Div dis pl ay mode button on the
analyzer and position the baseline of the display to the
bottom graticule line with the Vert Position control. Center
the disp lay with the Horizontal Position control.
g. Now depress the 10 dB/Div ( LO G) display push·
button on the analyzer. Display should now resemble that
shown in Fig . 2·1.
NO TE
When the oscilloscope has a CRT with Pl phosphor, a
viewing hood wiff help shield ambient light and
enhance the display information.
2. Calibrate the sweep span and referen ce level, using the
7K
ll Ca librator signal and the procedure described in the
Spectrum An alyzer manual.
APPLICATIONS
The gain and 75 n to 50 n conversion of the 7K l1
provide the ina-eased se nsitivi ty that is necessary for the
Spectrum Analyzer
(7l 12) to make a ll CATV performance
tests. Tektronix "Proof of Performance" brochure provides
procedures for making
the se measurement s. The fo ll ow ing
describes a typical applicati on for the 7K11/7l 12.
Sensitive Int ermod ul ation Measurement s:
a. Connect the test point of the CATV system to the
7K1 1
RF INPUT connector.
b. Select a Frequency Span/Dill
so the spectrum of one
channel
is displayed (0.5 MHz). Tune the Spectrum
Analyzer Center Frequency to
the center of the channel.
®
Operation-7Kl1
c. Adjust the Re so lution and sweep speed for a flicker-
free disp lay with distinct video and sound carrier. Adjust
the sweep speed
so the video information moves across the
display and does not obscure any 1M (beat) products.
Switch
in filters, ad just Resolution, per sis tence, and Inten·
sity, until the carrier
to noise amplitude ratio is optimized
d. U se the 10 dB/Oiv display mode and check for a peak
car
ri er to noise ratio that is 50 dB or more.
e. Che ck the di splay for 1M products above and below
the p ic tur e ca rri er by tuning slowly either si de of the carrier
si gnal or switch the ce nter frequency fr om Ce nter to Start
position. Once a beat
is located, co mp are the peak video
ca rrier level to the peak intermodulation (beat) si gnal leve l.
See Fig . 2·2.
f. Check to ensure that the beat signal is not a product
of the 7K
l1 amplifier by changing the input attenuation
(REFERENCE LE V EL ) a few dB (e.g ., 3 dB). If the change
of the beat signal amplitude level is more than the input
attenuation change, the 7K
ll amplifier is producing the
s ign a l.
F ill . 2·2. Di splay showi nll inter modul a tio n , bo ..e t he pi cture cerrier.
2·3
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Section 3-7Kll
PERFORMANCE CHECK
Introduction
Th is section verifies the operatio nal performance of the
7K ll to the dlaracteristics specified in the Specifications
section. Verification
of the electrical characterist ics requires
sop
hi sticated test eq uipment; however, an incoming accept·
ance dleck procedure is provided in the first portion of this
sect
io n to dleek the instrument operation. This procedure
w
il l not measure specified parameters. The second po rt ion
of this section provides a list of test equipment and
procedures for measuring the specified parameters c lOd
characteristiC5.
OPERATIONAL CHECK ANO
INSTRUMENT
FAMILIARIZATION
This portion contains a sequen ce of procedures that
checks the instrument operation and will
hel p familiarize
you with the instrument operation. Because the 7K
11
Calibrat or and attenuator are very accurate, they are used
as the reference for this operational checkout.
Pr elimin ar y Prep ara tion
Perform the Preliminary Fr ont Pa nel Setup Procedure
that is described in the Operating Instructions so the system
display (amplitude and frequency span) is calibrated.
1. Check Frequency Ra nge (30 MHz to 890 MH z)
a. Apply the CA L OUT signal through the 75 n, 5 1/2
inch cable, to the RF INPUT and connect the RF OUTPUT
to the Spectrum Analyzer RF Input through a 50 n coaxial
cable.
b. Set the 7K
l1 and Spectrum An al yzer selectors as
fo
ll ows:
REFEREN
CE LEVEL
®
7K1,
+10 dBmV (Thi s is 20 dB
above the
cal ib rator +30
dBmV reference lellel so
harmonics
of the funda·
mental will spread across
the
900 MHz spectrum.)
Spectrum Analyzer
Center Frequency
500 MHz
Reference Level
(RF Attenua
tor at 0 dB) -30 dBm
Display Mode 10 dB/
Div
Freq. Span/ Di v 100 MHz
Resoluti
on 3 MHz
Time/
Di v Spectrum or 10 ms
Fig. 3·1. 50 MHz mark ers acrOH I 1 000 MHz display.
c. Check the 1000 MHz span for 50 MHz markers out to
900 MHz. Marker amplitude w ill decrease towards the
upper end of the spectr
um . Se e Fig . 3-1.
2. Check th e Calibrator Reference Level
a. Ch a ng e the Spectrum Analvzer Display Mode to 2
dB/Di ll . Tu ne the Center Frequency to the 50 MHz
fundamenta l. Uncouple the Freq Sp an/ D ill from the Re so-
lution and open tne d is pl ay to 10 MH z/ D iv. Resolution
sh ould remain at 3 M Hz . Change tne 7 K11 REFERENCE
LEVEL to +30 dBm
V,
3-1
Scllns bv OIl I5O llr u -Opl ;ons =>

Performance-7K 11
b. Disconnect the cable between the 7K11 RF OUTPUT
and the Spectrum Analyzer RF I nput and apply the
Spectrum Analyzer Calibrator signal
to its RF Input. Note
the amplitude
of the 50 MHz, -30 dBm signal.
c. Now apply the 7K11 RF OUTPUT to the Spectrum
Analyzer RF
Input and the CAL OUT (+30 dBmV) to its
RF INPUT. The amplitude difference between the
two
calibrator signals should be slight.
NOTE
Because of the additive tolerances of the lK11 and
Spectrum Analyzer Calibrators, plus the lK11 atten-
uator and amplifier, it is impractical to establish
limits. This comparison is only an operational check.
3. Check the Attenuator
NOTE
The attenuator accuracy is checked at the factory.
This check will detect component failure but it will
not check the tolerance characteristics. If the toler-
ance characteristics are to be checked, a reference
attenuator calibrated by the user or manufacturer to
specifications more rigid than the lK11 attenuator
must be used.
a. Apply the 50 MHz, +30 dBmV signal to the RF
INPUT and connect the RF OUTPUT to the RF Input of
the Spectrum Analyzer.
b. Set the
front panel controls as follows:
7K11
REFERENCE
LEVEL +30 dBmV
RF Attenuator
Reference Level
Display Mode
Freq. Span/Div
Resolution
Time/Div
3-2
Spectrum Analyzer
30dB
-20dBm
10 dB/Div
5MHz
.3 MHz
Spectrum
or 10 ms/Div
c. Tune the 50 MHz signal to the center of the graticule,
then open the display
by decreasing the Freq Span/Div to 2
MHz.
d. Adjust the signal amplitude with the Spectrum
Analyzer Variable Gain control
to a graticule reference line
(e.g., one division below the top line).
e. Check the 7K11 attenuator by increasing the settings
in 10
dB steps above +30 dBmV while decreasing the
Spectrum Analyzer RF attenuator setting in 10 dB incre-
ments and noting the difference in signal amplitude. Now
decrease the 7K11 attenuator settings below +30 dBmV
and increase the analyzer RF attenuator settings and note
the difference. Difference between the
two should not
exceed 1.5 dB.
f. Return the attenuators to +30 dBmV and 30 dB.
Switch
to the 2 dB/Div display mode and re-establish a
signal reference level
with the Variable Gain control.
g. Check the 1 dB steps of the 7K11 attenuator by
noting the decrease of signal amplitude on the display as
the attenuation is increased.
4. Check Sensitivity (-451 dBmV at 3 MHz
Resolution) --\
a. Switch the Spectrum Analyzer Display Mode to Lin
and add 30 kHz of Video Filter.
b. Increase the 7K11 attenuator setting 45 dB (REFER-
ENCE
LEVEL to 75 dBmV). Now increase the Spectrum
Analyzer
IF gain (selector and Variable) setting until the
average noise floor on the display rises one division.
c. Check that the amplitude of the signal is at least
twice the noise level ( ;;;. 2 div). See Fig. 3-2.
This completes the operational check
of the instrument's
performance.
If you desire to validate the specified
parameters (which requires sophisticated test equipment),
continue
to the next part of this section.
®

Fi g. 3-2. Mea su rin g sens itivity . SigMlltNel " 2X noi w.
PERFORMANCE VERIFICATION OF
SPECIFIED CHARACTERISTICS
The following procedures describe how to measure the
7Kl 1 characteristics as specifie? It does not include
internal adjustments
or checks. If the instrument fails to
meet specified performance requirements, the adjustment
procedure
will be found in the Serllice section under
Calibration.
History Information
The instrument and manual are continually ella lu ated
and updated. Circuits and manual procedures may be
modified. Information applicable to earlier instruments are
included either
as delliations within these steps or as a
subpart of the steps. The
se modifications are added at the
back of the manual as inserts or indicated in the procedure.
Equipment Required and Recommended
The following test equipment and fixtures are recom·
mended to perform this portion of the performance check.
Test equipment specifications are the minimum require·
ments for accurate checks. Substitute equipment must
equal or exceed these specifications.
The fixtures (attenuators, etc.) are used where necessary
to facilitate the procedure. The
se fixtures are available from
Tektronix,
In c., and can be or dered through your local
Tektronix Field Office or representatille.
®
Performance-7K11
EQUIPMENT LIST
NOTE: This equipment is also re quired to recatibrate the
instrument.
1. Spectrum Analyzer ensemble
(Oscil loscope and 7L12 or
7L13 Spectrum Analyzer). NOTE: Storage or lIariable
persistence oscilloscopes are desirable for spectr um analysis.
Tektronix 7000·Seri
es storage Of lIariable persistence
oscilloscopes (7613, 7623, 7313) accept three plug·in
wi dth s. The 7L13 Specrrum Analyzer requir es three plug·in
widths; therefore, the 7K 11 /7 L1 3 ensemble must be used
with non·stora
ge mainframes such as 7704A and 7904.
2. Leveled sweeper or signal generators that colier the
frequency range
of 30 MHz to 890 MH z. (Use a power
meter to lIerify that the generator
output remains constant
oller this frequency range.)
a) Hewlett Packard Model 86BOA with 86602A RF
Section; or
b) Hewlett Packard Model B08E (10
MHz to 480 MHz)
plus Model 612 A.
The Model 612A does not halle a lelleled output; therefore,
it must be adjusted manually
as the frequency is changed.
3. Vector Voltmeter with a frequency range
of 50 MHz, to
measure
the Calibrator +30 dBmV output lellel tolerance:
Hewlett Packard
Model 8405A.
4. Dig ital Counter to check 50 MHz accuracy of the
ca librator: Tektronix 7D 14 Digital Counter with a readout
7000·Series oscilloscope, or a DC·502 with the
TM·500·Series.
5. Type BNC 50 n to 75 n Minimum Loss Attenuator:
Tektronix Part No. 011-0057·00.
6. Two 5:1, 50 n Attenuators: Tektronix Part No .
011-0060-01.
7. Two 18 inch, 50 n low lo ss coaxial cables with BNC to
BNC connectors: Tektronix Part No. 012·0076·00.
8. BNC "T" Connector: Tektronix Part No. 103-0030-00.
9. 75 n Feedthrough Termination: Tektronix Part No.
011-0055-00.
3·3
Scans bl' Olltsource-Options ::>

Performance-7K11
PERFORMANCE CHECK
1. Check the Calibrator Frequency (Accuracy 50
MHz ±0.01%)
The frequency of the calibrator may be checked by an
accurate frequency counter, such as Tektronix 7D14 Digital
Counter Plug-In
Unit with a readout 7000-Series Oscillo-
scope or a DC-502 with TM-500-Series. No procedure for
this check is provided, because the CAL OUT signal can be
connected through the CATV Preamplifier unit to the input
of the counter and the frequency readout noted.
2. Check Calibrator Output (+30 dBmV ±0.3 dB)
The output of the calibrator contains harmonics; there-
fore, direct measurement
is not possible.
Vector Voltmeter Method (Hewlett Packard Model
8405A
Vector Voltmeter)
a. Terminate the "A" probe with a BNC 75 n feed-
through termination
and connect the probe, through the
termination,
to the CAL OUT connector on the 7K11.
b. Switch the Vector Voltmeter frequency to 50 MHz.
c. Check for an RMS reading between 31.2 mV to 32.1
mV (+30 dBmV is 31.6 mV RMS into 75 n)_ If output is
out of specification, refer to Calibrator Output adjustment
in the Calibration Procedure.
3. Check RF Attenuator Accuracy (Within
±0.2 dB + 1% of the dB readout)
3-4
NOTE
The RF attenuatoraccuracy is checked at the factory
to ensure that it is within specifications. Step #3 in
the first portion of this section will detect any
component failure within the attenuator but it will
not check the tolerance characteristics. If the exact
attenuation error of the selector is required, a
reference attenuator, calibrated by the user or manu-
facturer to more rigid specifications than the 7K11
RFattenuator, must be used.
4. Check the Frequency Range and Display Flat-
ness (±2 dB, 30 MHz to 890 MHz, ±1 dB, 50 MHz
to 300 MHz).
a. Set the 7K11 and Spectrum Analyzer controls as
follows:
7K11
REFERENCE
LEVEL
10 dBmV
Spectrum Analyzer
Center Frequency
Reference Level
(RF at 0 dB)
Display Mode
Freq. Span/Div
Resolution
Time/Div
50 MHz
-30dBm
2 dB/Div
100 MHz
3 MHz
Spectrum
or 10 ms
b. Apply the output of a leveled sweeper or signal
generator
~hrOUgh a 50 n to 75 n Minimum Loss Atten-
uator,
to the RF INPUT of the 7K11. Connect the RF
OUTPUT to he RF I nput of the Spectrum Analyzer.
c. Tune the sweeper or signal generator to 50 MHz and
adjust the output for a signal reference level of approx-
imately 5 divisions on the display.
d. Check the frequency range and flatness of the
7K11/Spectrum Analyzer ensemble,
by sweeping or tuning
the signal generator(s)
from 30 MHz to 890 MHz. Display
flatness must
be within 1 dB from 50 MHz to 300 MHz
with reference to 50 MHz, and within 2 dB from 30 MHz to
890 MHz. Frequency range must equal or exceed 30 MHz
to 890 MHz.
5. Check Intermodulation Distortion
The 7K11 will not degrade.the 1M performance specifi-
cations
of the Spectrum Analyzer. Intermodulation distor-
tion from two 0 dBmV signals is down 80 dB or more.
One method of checking this specification is to check
the 7K
11 /Spectrum Analyzer ensemble to ensure that the
1M distortion characteristics of the Spectrum Analyzer have
not been degraded. Check by performing the procedure
described in the Spectrum Analyzer manual. NOTE:
Use a
50 n to 75 n Minimum Loss Attenuator between the 50 n
signal source and the RF INPUT of the 7K11.
®

Performance-7K11
7Kl1
Over the linear operating range of the 7K l1 amplifier,
the gain remains relatively constant or on a 1:1 ratio. The
ratio
of intermodulation products (3rd order) from two or
more input signals is about 3:1. This analogy is used to
extrapolate the 1M distortion figure of the 7Kl1 by the
following procedure.
REFERENCE
LE VEL +30dBmV
Spectrum Analyzer
a. Apply two signals within the frequency range of the
7Kl1 and separated approximate
ly 2 MHz to 10 MHz,
through two 5X attenuators !for isolation). a BNC "T"
connector, then through a 50 n to 75 n Minimum Loss
Attenuator, to
the 7Kl 1 RF INPUT. Fig. 3-3 illustrates this
setup.
b. Set
the front panel controls and selectors as follows:
Signal Ge nerator
500 MHz - 1000 MHz
7000 Series
Oscilloscope
[1]
.
, .
, -
. .
. -
~ -
Display Mode
RF Attenuator
Reference Level
Video Filter
Center Frequency
Freq Span/
Di v and
Resolution
~~l
i'J .•
o
i 0
;0' " I '
7K11 _=- =< C"' --" __ Sp&<;tr om
"" ~-- - .... -f:- '" Analvzer
" @ !:;' i ~ - ~ /
r:PUT- -- ~ ~' U; - • \!7 ~ ~
fOP ••• lsi :"
-
L ___ ..... ~ -- 50 n C::08>C cable
~
r ,
5X auenoators
for isolation -
BNe "T" c::onneetor end
50 n to 75 n minimom
1 01$ attenoator
10 dB/Div
OdB
-30 dBm
30 kHz
Tuned midway between
the two applied signals
Span should be wide
enough to observe the two
input signals and their
1M
products. Resolution set
for optimum sensitivity.
UHF Signal
Generator
10 MHz - 500 MHz
~ .. ~ . \
•• •
:
1" .
~i . .. . ~
o • ~ - •
I
Fig. 3-3. Equipm ent IIttup end oon nac::tio ns n eeltSNl ry to measure intermodulation distortion.
® 3-5
Scans bv Olltsollrce~Options =>

Performance- 7Kll
c. Adjust the output of the two si gnal sources until b ot h
signals are full screen or at the reference level.
NOTE
When the 7K11 REFERENCE LEVEL is +30 dBm V,
the input to the amplifier stage is 0 dBmV, because
the attenuator is between the amplifier and the RF
INPUT connector.
d. Decrease the 7K 11 REFERENCE LE VE L (atten·
uator) setting in 10 dB steps and increase the Spectrum
Analyzer RF Attenuator setting in 10 dB s tep s unt il the
intermodutati on signals appear on the display. See Fig. 3-4.
NOTE: Verify
the 2: 1 ratio of the 1M products by noting
the amplitude increase for a
10dB change in the 7 K11
in put lev e l. If the amplifier is not overdriven, the amplitude
le ve l of the 1M products w ill increase 20 dB with a change
of 10 dB attenuation. When the amplifier
is overdriven,
additional spurs w
ill be generated either side of the 1M
signals.
If th is occurs, increase the 7K l1 RF ATTEN·
UA TOR setting and decrease the Spectrum Analyzer RF
Attenuator setting.
3. Note the
le vel of the 1M signals; then de termine by
extrapolating, the
level of the 1M signals bel ow 0 dBmV .
F
or example: A cha nge of 20 dB in attenuation would add
40 dB to the noted level of the 1M signals below the
reference level. If the level of the 1M signals is 45 dB below
the top of the graticule, with the signal input to the 7K l1
20 dB above the reference level, the interpolated 1M
distortion would equal (45 dB + 40 dB)
85 dB.
This completes
the performance check for t he 7 K 11 . It
wi ll now perform within the specifications described in
Section 1.
3-6
B. An overdriv~n amplifie r gen erates additiona l spurii.
F ig . J.4. Oisplay of 1M distortion and an ove rdri ven amplifier.
@
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Section 4-7K11
\
SERVICE INSTRUCTIONS
Introduction
This section includes data relative to servicing the 7Kll.
This data includes circuit description, calibration, preven-
tive maintenance and corrective maintenance procedures
that describe replacement procedures for components and
assemblies.
CIRCUIT DESCRIPTION
The CATV Preamplifier unit contains an attenuator
assembly with a readout circuit, a crystal controlled 50
MHz oscillator with a calibrated +30 dBmV output, and a
regulated power supply.
The attenuator assembly consists of an amplifier and
selectable 1, 2,4, 10, and 20 dB attenuator pads that can
be switched into the signal path by cam switches S900 and
S902. This attenuator provides 1 dB
to 79 dB of atten-
uation in 1 dB or 10 dB steps. Readout resistors are added
or removed
in sequence with the attenuator switching to
furnish readout information to the mainframe readout
circuit.
Cam 5 of S902 closes only in the 0 dBmV position
to eliminate the extra 0 digit of the readout through the 0
to 9 dBmV range.
With both cam switches
in the 0 dBmV position, the
signal path from the RF INPUT is ac coupled through C900
to the input of an IC amplifier U900. This amplifier has an
input impedance of approximately 75
il and a gain of
25 dB. The
output of the amplifier drives the 50 il RF
OUTPUT connector through a 6 dB matching pad. Con-
version from dBmV at 75 il to dBm at 50 il is 49 dB.
Therefore, a +30 dBmV signal
is converted to a -30 dBm
signal at the output, when the REFERENCE LEVEL
selector (attenuator)
is set to +30 dBmV. A +30 dBmV
signal at the
RF INPUT is attenuated 30 dB through AT912
and AT914, amplified 25 dB by U900, and attenuated 6 dB
through AT916
to a level of +19 dBmV or -30 dBm.
Output imPesiance is 50 il.
The 50 MHz calibrator is similar to the calibrator in the
7L12 or 7L13. Its
output level is adjusted to +30 dBmV
with R956.
®
CALIBRATION
There are only two calibration steps for the 7Kll.
Check the +24 V regulated supply and adjust the output of
the 50
MHz calibrator.
1. CheckL24 V Regulated Power Supply
a. Remove the oscilloscope and 7Kll left side panels to
expose the left siQe of the 7Kll when the instrument is
installed in the mainframe.
b. Connect a voltmeter between chassis ground and the
feedthrough capacitor C918
(see Fig. 4-1).
c. Check the +24 V regulated supply. Must measure
24 V ±2.4 V.
2. Adjust the Calibrator Output (+30 dBmV
±0.3 dB)
Since the output of the calibrator contains harmonics,
direct power measurements are not possible. The following
method will check and adjust the output level to specifi-
cations.
Vector Voltmeter Method (Hewlett Packard Model 8405A
Vector Voltmeter)
a. Terminate the "An probe, with a BNC 75 il feed-
through termination and connect the probe through the
termination,
to the CAL OUT connector on the 7Kll.
b. Switch the Vector Voltmeter frequency to 50 MHz.
c. Check that the RMS reading is between 31.2 mV to
32.1 mV (+30 dBmV is 31.6 mV RMS, into 75 il).
d. The calibrator output level can be adjusted by
removing
the 7Kll and oscilloscope left side panels to gain
access
to the 7 Kll calibrator. Adjust R956 (Fig. 4-1) for an
output level of +30 dBmV (31.6 mV RMS).
4-1

Service-1K11
Fie. 4-1. Side pIOn", .,mov_ 10 sho,,", 11'o,10QI1ion of C9ta ,nd 1M
CIIlibt,tor output _jun,",nt R956.
MAINTENANCE
Introduction
The following describes: recommended procedure for
reducing or preventing instrument malfunction, trouble·
shooting. and corrective maintenance to repair the
instrument. Preventive maintenance improves instrument
reliability. Should the instrument fail to function properly,
corrective measures should be taken immediately; other ·
wise, additional problems may develop within the
instrument.
PREVENTIVE MAINTENANCE
Preventive maintenance consists of cleaning, visual
inspection, performance check, and if needed, a recalibra·
tion. The preventive maintenance schedule should be based
on the environment the instrument is operated in and the
amOllnt of use. Under average conditions (laboratory
situation) a preventive maintenance check should be per·
formed every 1000 hours of instrument operation.
Cleaning
Clean the instrument often enough to prevent dust or
dirt from accumulating in or on it. Dirt acts as a thermal
insulating blanket and prevents efficient heat dissipation. If
it becomes damp it can provide electrical high resistance
leakage paths between conductors
and/or components.
Exterior. Clean the
dust from the outside of the
instrument by wiping or brushing the surface with a soft
cloth or small brush. Hardened dirt may be removed with a
cloth dampened in water th at contains a mild detergent.
Abrasive cleaners should not be used.
4·2
In terior. Normally the interior of the inmument will not
require cleaning unless it has been left
out of the
oscilloscope plug·in compartment and uncovered for an
extended period
of time. Clean the interior by loosening
accumulated
dust with a dry soft brush, then remove the
loosened dirt with low pressure air to blow the dust clear.
(High velocitv air can damage some components .) Hardened
dirt
or grease may be removed with a cotton tipped
applicator dampened with a solution
of mild detergent in
water. Abrasive cleaners should
not be used. If the circuit
board assemblies need cleaning, remove the circuit board by
referring to the instructions under Corrective Maintenance
in this section.
After cleaning, allow the interior
to thoroughly dry
before applying power
to the inst rument.
Do not clean any plastic materials with organic
cleaning solvents SlJch as benzene, toluene, xylene.
acetone or similar compounds
becau~ th ey may
damage the plastic.
Visual Inspection
After cleaning, carefully check the Instrument for such
defects
as defective connections, damaged parts. and
improperly seated transistors and integrated circuits. The
remedy for most visible
defects is obvious; however. If
heat-damaged parts are discovered, try to determine the
cause of over.heating before the damaged part is replaced,
otherwise the damage may be repeated.
Transistor and Integrated Circuit Checks
Periodic checks of the transistors and integrated circuits
are not recommended. The best measure of performance is
the actual operation of the component in the circuit.
Performance of these components is thoroughly checked
during the performance ched<
or recalibration, and any
substandard transistors or integrated circuits will usually be
detected
at that time.
Performance Checks and Recalibration
The instru ment performance should be checked after
each 1000 hours of operation or every six months if the
instrument
is used intermittently to ensure maximum
performance and assist is locating defects that may not be
app
arent during regular operation.
®

TROUBLESHOOTING
The ability to recognize and locate trouble is acquired
with experience and
as you become familiar with the
instrument. The following are a few aids and suggestions
that may assist
in locating a problem. After the defective
assembly or component has been located, refer
to Cor-
rective Maintenance part
of this section for removal and
replacement instructions.
Troubleshooting Aids
Diagrams. Block and circuit diagrams on foldout pages in
the Diagrams section contain significant waveform and
voltage information. Refer
to the Electrical Parts List
section for a description of
all assemblies and components.
NOTE
Corrections and modifications to the manual and
instrument
are described on inserts bound into the
rear of the manual. Check this section for changes
and corrections
to the manual or the instrument.
Circuit Board Illustrations. Electrical components,
connectors, and test points are identified on circuit board
diagrams located on
the inside fold of the corresponding
circuit diagram or
the back of the preceding diagram. This
allows
the troubleshooter to trace and check the operation
of each circuit, and physically locate circuit components.
Wiring Color Code. Color coded wires are used
to aid
circuit tracing. Power supply,
DC voltage leads have either a
white background for positive voltage or a violet back-
ground for negative voltage. Signal wires and coaxial cables
use an identifying one-band or two-band color code.
Multiple Terminal (Harmonica) Connector Holders. Most
intercircuit connections are made through pin connectors
which may be mounted
in a harmonica type holder. The
terminals
in the holder are identified by numbers. Con-
nector orientation
to the circuit board is keyed by triangles
on the holder and
the circuit board (see Fig. 4-2). All
connectors are identified on the schematic and board with
'P' numbers.
Resistor Color Code. Brown composition resistors,
metal-film resistors (identificable by their gray body color)
and some wire-wound
res~stors '(usually light blue or
graYilreen) are used in the 7K11. The resistance value of a
wire-wound resistor
is printed on the body of the compo-
nent. The resistance value of a composition resistor or
metal-film resistor
is color-coded on the component with
EIA color-code (some metal-film resistors may have the
value printed on the body).
®
Service-7K11
Fig. 4-2. Mult . circuit board connectors.
Capacitor Marking. The capacitance value of a common
disc capacitor or'small electrolytic
is marked in microfarads
on
the side of the component body. The white ceramic
capacitors are color coded
in picofarads.
Diode Color Code. The cathode of each glass encased
diode
is indicated by a stripe, a series of stripes or a dot.
Fig. 4-3 illustrates diode types and polarity markings
that
are used in this instrument.
Transistor and Integrated Circuit Electrode Config-
urations. Lead identification for the transistors, MaS
FET's, and IC's are shown in Fig. 4-4.
General
The following procedure is recommended to isolate a
problem and expedite repairs.
1. Ensure
that the malfunction exists in the instrument.
Check the operation of associated equipment and the
operating procedure of the 7K11
(see Operating Instruc-
tions).
2. Determine and evaluate
all trouble symptoms. Try to
isolate the problem to a circuit or assembly.
3. Visually inspect the area or the assembly for such
defects
as broken or loose connections, improperly seated
components, over-heated or burned components, chafed
insulation or cracked insulators, etc. Repair or replace
all
obvious defects. In the case of overheated parts, try to
determine the cause of overheating and correct before
applying power.
4-3

Service-7K11
Fig. 4-3. Diode polarity markings.
Plastic Cased Transistors
Integrated Circuit
10
1
10
Fig. 4-4. Electrode configuration for socket mounted transistors
and IC's.
4-4
4. Check the calibration adjustments of the affected
circuit, if applicable. Before changing the setting of any
adjustment, note its position
so it can be returned to its
original setting. This
will facilitate recalibration after the
trouble has been located and repaired.
5. Semiconductor failures account
for the majority of
electronic equipment failures. Most semiconductor devices
(transistors and IC's)
are socket-mounted, therefore, substi-
tution is often the most practical means for checking their
performance. The
following guide lines should be followed
when substituting these components:
a. F~st determine that circuit voltages are safe for
the subs~ted component, so the replacement will not
be damaged.
b.
Use only good components for substitution.
c. Turn tile power off before a component is
substituted.
d. Be sure the component (transistor or IC) is
inserted properly in the socket (see Fig. 4-4).
e. After the operational check, return the good
components
to their original sockets to reduce calibra-
tion time and run-in period.
NOTE
If a substitute is not available, check the transistor or
MOS FET with a dynamic tester such as the
Tektronix Type 576 Curve
Tracer. Static type testers,
such as
an ohmmeter, can be used to check resistance
ratios across some semiconductor junctions
if no
other
method is available. (Do not measure resistance
across
MOS FEr's because they are very susceptible
to static charges.)
Use the high resistance ranges (R X
1 k or higher)
so the external current is limited to less
than 2 mA. If uncertain, measure the external current
with
an ammeter. Resistance ratios across the base·
to-emitter or base-to-collector junctions usually run
100: 1 or higher. The ratio is measured by connecting
the meter leads across the terminals, noting the
reading, then reversing the leads and noting the
secondreading.
CORRECTIVE MAINTENANCE
Corrective maintenance consists of component
replacement and instrument repair. Special techniques
and
procedures, required to replace components in this instru-
ment,
are described here.
®

Obtaining Replacement Parts
All electrical and mechanical parts replacements can be
obtained through
your local Tektronix Field Office or
representative. Many of the standard electronic compo-
nents, however, can be obtained locally in less time than
that required to order from Tektronix, I nco Before pur-
chasing or ordering replacement parts, consult the Parts List
for value, tolerance and rating.
The Parts section contains
instructions on how
to order these replacement parts.
It is best to duplicate the original component as closely
as possible. Parts orientation and lead dress should also
duplicate those
of the original part because some compo-
nents are oriented to reduce or control circuit capacitance
and inductance. After repair,
the circuits may need recali-
bration.
Soldering Technique
Disconnect the instrument from its power source
before replacing orsoldering components.
The components that are soldered on the circuit boards
can be replaced
by using normal circuit board soldering
technique.
Use a pencil type, 25 watt soldering iron and a
desoldering tool
to remove the old solder. Heat sink the
leads of active components; such as diodes or transistors,
with needle nose pliers. Avoid excessive
or prolonged heat
at
the connection because this could cause the board run to
separate from the board. Use a good quality solder (63/37)
to resolder the new component on the board.
Diode Checks
Most diodes can be checked in the circuit by taking
measurements across
the diode and comparing these with
voltages listed on the diagram. Forward-to-back resistance
ratios can usually be
taken by referring to the schematic
and pulling appropriate transistors and pin connectors
to
remove low resistance loops around the diode.
®
Do not use an ohmmeter scale with a high external
current to check the diode junction.
Do not check
the forward-to-back resistance ratios
of tunnel diodes
or mixer diodes.
Service-7Kll
Integrated Circuit (IC) Checks
Integrated circuits are most easily checked by direct
replacement. When substitution
is impossible, check input
and output signal states as described in the circuit descrip-
tion and on the diagram. Lead configuration for the IC used
in this instrument is provided by Fig. 4-4.
Check calibration and performance after a faulty compo-
nent has been replaced.
If the above procedure fails to locate the trouble, a more
detailed analysis must be performed. The Circuit Descrip-
tion describes the operational theory of each circuit and
may aid
to further evaluate the problem.
Replacing Assemblies, Sub-as'semblies and
Components
,. .
The assemblies and sub-assemblies are easily removed
and replaced. The following procedures describe how
to
replace these assemblies and components.
To remove the assemblies: 1) Disconnect the semi-rigid
coaxial
conductors. Use a 5/16 open end wrench to loosen
the nuts. 2) Remove the back plate plug-in guide and
interface circuit
board. 3) Remove the screws holding the
mounting brackets for the attenuator assembly. 4) Set the
attenuator switch for 00 readout, then remove the front
panel knobs. 5) Slide the assembly back to clear the switch
shaft and remove.
The Interface circuit board
is held onto the plastic back
plate plug-in guide. Use a tapered punch
or tool such as
needle nose pliers
to pry the retainer clips up and free the
board.
When installing
the semi-rigid connectors, tighten the
nuts until they are just snug.
Cam Switch Replacement
Repair of cam-type switches should be undertaken
only
by experienced maintenance personnel. Switch
alignment and spring tension
of the contacts must be
carefully maintained for proper operation
of the
switch. For assistance in maintenance
of cam-type
switches, contact your local Tektronix Field Office or
representative.
4-5
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