Tektronix Z User manual

IV l/X IN I U A L
Tektronix, Inc.
S.W. Millikan Way • P. O. Box 500 • Beaverton, Oregon • Phone Ml 4-01 1 • Cables: Tektronix
Tektronix International A. G.
Terrassenweg 1A • Zug, Switzerland • PH.042-49192 • Cable: Tekintag, Zug Switzerland • Telex 53.574
070-251

WARRANTY
All Tektronix instruments are warranted
against defective materials and workman
ship for one year. Tektronix transformers,
manufactured in our own plant, are w ar
ranted for the life of the instrument.
Any questions with respect to the w ar
ranty mentioned above should be taken up
with your Tektronix Field Engineer.
Tektronix repair and replacement-part
service is geared directly to the field, there
fore all requests for repairs and replace
ment parts should be directed to the Tek
tronix Field Office or Representative in your
area. This procedure w ill assure you the
fastest possible service. Please include the
instrument Type and Serial number with all
requests for parts or service.
Specifications and price change priv
ileges reserved.
Copyright © 19 0 by Tektronix, Inc.,
Beaverton, Oregon. Printed in the United
States of America. All rights reserved. Con
tents of this publication may not be repro
duced in any form without permission of
the copyright owner.

CONTENTS
W arranty
Section 1 Specifications
Section 2 Operating Instructions
Section 3 Circuit Description
Section 4 Maintenance
Section 5 Calibration
Section Accessories
Section 7 Parts List and Diagrams
® Type z

m
TYPE Z PLUG-IN UNIT
CALIBRATED DIFFERENTIAL COMPACTOR
.1 00 0 CM. DYNAMIC SCALE LENGTH
/UUU V.f'l- " ■ ■ ’ — _
COMPARISON VOLTAGE -x
VOLTS/CM
(ATTENUATION!
VAR. ATTEN
I PUSH TO j
0 I 5 C O N N E C T
SIGNAL j
ptSCONN Ed
signal u n i a eh
ATTEN.
GAIN
ADJUST b a ia n c e
'position
VOLTS/CM
{ A T T I N U A T I O N )
onto on.
PORTIA I
rlATEONIX,
Type Z
http //manoman.sqhill.com

O INI 1
SPECIFICATION
General Information
The Type Z Plug-In Unit is a calibrated differential com
parator preamplifier designed for use in all Tektronix
Type 530-, 540-, 550-, or 580-Series Oscilloscopes. The
unit may be used for three different modes of operation:
(1) as a conventional plug-in preamplifier, (2) as a differential
input preamplifier, or (3) as a calibrated differential com-
pa rator.
As a conventional preamplifier, the Z Unit alone has a
risetime of 24 nanoseconds and a maximum sensitivity of
0.05 volt per centimeter of deflection. Table 1-1 summar
izes the risetimes and bandwidths available when the Z
Unit is used in combination with various types of Tektronix
oscilloscopes.
TABLE 1-1
Z Unit and
Type.- Risetime in Nanoseconds* Bandwidth, —3 db,
Megacycles/Seconcl*
532 70 5
531 or 535 39 9
53 40 9
531 A, 533, or 535A 35 10
541, 543, 545,
541 A, 545A,
551, or 555
27 13
581 or 585** 27 13
*For signals which do not overscan the graticule.
**Type 81 Adapter must be used.
In differential input mode of operation, the dynamic
range of r'zlOO volts allows the application of common
mode signals up to 100 volts to be applied to the unit with
out attenuation. The common-mode rejection ratio of
40,000 to 1 at dc or low frequencies allows measurement
of differential signals less than 50 mv in amplitude on
7+c 100-volt common-mode signals.
As a calibrated differential comparator, the Z Unit has
an effective screen height of ih2000 cm at maximum sensi
tivity. Within the dynamic range of :J:100 volts, calibra'ed
±DC comparison voltages can be added differentially to
the input waveform to permit a maximum of 0.005% or
5 mv per mm to be accurately resolved.
Vertical Deflection Factors
0.05 to 25 volts per centimeter in nine calibrated steps;
also continuously variable (uncalibrated) between steps and
up to 0 volts per centimeter.
Input Impedance
1 megohm :Ul % paralleled by 24 pf.
Maximum Allowable Combined DC and Peak AC
Input
00 volts, ac-coupled.
Maximum Common-Mode Signal
r'rlOO volts at 0.05 volt per centimeter. Higher voltages
are permissible with larger vertical deflection factors.
Common-Mode Rejection Ratio
40,000 to 1 at 0.05 volt per centimeter with a 1-kc sine
wave, lower at other sensitivities and higher frequencies.
At 0.05 volt per centimeter, a 200-volt (p-p) 1-kc common
mode signal produces less than 1 mm of vertical deflection.
Comparison Voltages Available
Three voltage ranges are provided: 0 to r‘-l volt, 0 to
~10 volts, and 0 to : 100 volts. An accurate 10-turn
potentiometer is used to select the comparison voltages
over these ranges.
Comparison Voltage Regulator
A regulator circuit maintains comparison voltages es
sentially constant and independent of normal power supply
voltages supplied by the oscilloscope.
1-1

Specifications — Type Z
Comparison Voltage Accuracy
Within 5 millivolts (0.5%) on the ±l-volt range.
Within 20 millivolts (0.2%) on the ± 10-volt range.
Within 150 millivolts (0.15%) on the ±100-volt range.
Maximum Trace Shift
2 mm due to input grid or gas current.
Comparison Voltage Drift
Less than 0.1 % per 100 hours operation.
Temperature compensated over normally expected tem
perature range. Air filter in oscilloscope should be main
tained clean, particularly when using the Z Unit.
10-Turn Potentiometer Linearity
0.05%
Measurement Resolution
Resolution accuracy, at 100-volts comparison voltage—
0.005%
Maximum resolution—5 millivolts per millimeter.
Transient Response and Permissible Signal Volt
age Rate of Change
Rate of rise—1 volt per nsec, maximum. If this rate
is exceeded, grid current will flow in the input stages.
Rate of fall—1 volt in 5 nsec, maximum. If this rate is
exceeded, the amplifier will momentarily cut off. If over
driven by a sufficiently fast pulse, the amplifier will ‘‘run
down" linearly at the above rate.
Because of the wide dynamic amplitude capabilities of the
Z Unit, transient response is a function of signal amplitude.
Mechanical Specifications
Construction—Aluminum-alloy chassis.
Front panel—Photo-etched.
Net weight— pounds.
Accessories
2—Instruction Manuals
1-2 ®I

A front-panel view of the Type Z Unit is shown in Fig. 2-1.
In addition, a brief functional description is given of the
front-panel controls, input connectors, Securing Rod, and
Mechanical Lock.
Connecting the Z Unit to the Oscilloscope
Connect the Z Unit to the associated oscilloscope by
inserting the unit into the plug-in compartment and tighten
ing the Securing Rod. With the Intensity control of the
oscilloscope turned fully counterclockwise, switch on the
oscilloscope power. Normally it is necessary to wait a few
minutes for the oscilloscope and plug-in to warm up and
stabilize. Then turn up the intensity and set the oscilloscope
triggering controls to produce a free-running sweep. Posi
tion the trace on the screen using the POSITION control
and the oscilloscope beam-position indicators.
Preliminary Operational Adjustments
After the Z Unit has warmed up and stabilized, check
its operation to see if adjustment of one or more of the
following controls is necessary. Be sure that the oscilloscope
used in conjunction with the Z Unit is correctly calibrated in
the vertical-deflection circuit, and that the calibrator output
voltage is correct.
1. Amplifier DC Balance
If the trace cannot be centered on the screen when -he
POSITION control is set near midrange, the AMP DC BAL
adjustment (see Fig. 2-2) must be checked. Need for this
adjustment arises mostly when the Z Unit is transferred
from one oscilloscope to another. To make the adjustment,
set the POSITION control to midrange, remove the left
side panel from the oscilloscope, and adjust the AMP DC
BAL control to position the trace behind the horizontal
centerline of the graticule.
2. Differential Balance
Differential balance may be quickly checked by applying
100 volts of calibrator signal to both input connectors. Set
both VOLTS/CM switches to .05, the AC-DC switches to
DC, and the Mode switch to A-B DIFF. Ignoring the posit ve
and negative spikes, adjust the DIFF. BAL. control to elimin-
SECTION 2
OPERATING
INSTRUCTIONS
ate any square-wave response (that is, to obtain a straight-
line appearance of the trace).
3. Variable Attenuator Balance
Any vertical shift of the oscilloscope trace when the VAR.
ATTEN. control is rotated, with no input signal applied,
indicates need for adjustment of the variable attenuator
balance. This adjustment must be made in conjunction
with the differential balance adjustment (step 2) due to
interaction between the circuits. Repeat the two adjust
ments until both are correct.
Set the Mode switch to A ONLY and remove any input
signals. Adjust the VAR. ATTEN. BALANCE control to
eliminate any vertical shift of the crt trace as the VAR.
ATTEN. control is rotated. Check to see if the trace can
be centered as described in step 1 (Amplifier DC Balance).
If not, repeat step 1.
4. Gain
The gain adjustment should be checked periodically to
assure correct vertical deflection factors. It should also be
checked when the Z Unit is transferred from one oscilloscope
to another. The adjustment is made using the calibrator
signal from the oscilloscope.
Set the Mode switch to A ONLY and apply 200 milli
volts of calibrator signal to the A input connector. Make
sure the VAR. ATTEN. control is set fully clockwise. Set
the A VOLTS/CM switch to .05 and rotate the GAIN AD
JUST control for exactly 4 centimeters of vertical deflection.
Input Signal Connections
It is often possible to make signal connections to the
Z Unit with short-length, unshielded test leads. This is par
ticularly true for high-level, low-frequency signals. When
such test leads are used, you must also use a ground con
nection between the oscilloscope and the chassis of the
signal source. (Note: Excessively long test leads may cause
parasitic oscillations.)
In many applications, however, unshielded leads are
unsatisfactory for making signal connections because of
pickup resulting from magnetic fields. In such cases, shielded
cables should be used. You must be sure that the ground
conductors of the cables are connected to the chassis of
both the oscilloscope and the signal source.
In high-frequency work it is usually necessary to terminate
signal sources and connecting cables in their characteristic
2-1

Operating Instructions — Type Z
VAR, ATTEN.— Varies the verti
cal deflection factors between
ranges of the VOLTS/CM con
trols.
Polarity— Selects the com par
ison voltage p olarity.
VOLTS/CM — Selects the
cal deflection factors. verti-
A INPUT— Connector for coupl
ing input dc or ac voltages to
pream plifie r.
AC-DC— Determines whether
Input signals are dc coupled or
ac coupled.
PUSH TO DISCONNECT
NAL— Disconnects signal
pream plifier input.
DIF F. BAL.— Adjusts the
am plifier for maximum
ferential rejection ratio.
PUSH TO DISCONNECT SIG
NAL— Disconnects signal from
pream plifier input.
AC-DC— Determines whether
input signals are dc coupled or
ac coupled.
B INPUT— Connector for coupl
ing Input dc or ac voltages to
pream plifier.
Range— Selects the appropri
ate comparison voltage range.
Mechanical lock— Locks Heli-
dia l when pressed dow nward.
H eiidial— Adjusts the com
parison voltage over the range
selected by the Range switch.
VAR. ATTEN, BALANCE— A d
justed to prevent vertical trace
shift as the VAR. ATTEN con
trol Is rotated.
POSITION— Sets the vertical
position of the trace on the
oscilloscope screen..
VOLTS/CM— Selects the ve rti
cal deflection factors. GAIN ADJUST— Sets the de
flection factors of the pre
am plifier to agree with the
front panel markings.
Fig. 2-1. Functions of front-panel controls, input connectors. Securing Rod, and M echanical Lock.
2-2
http //manoman.sqhill.com

Operating Instructions — Type Z
Fig. 2-2. Left rear side view of the Z Unit showing location of the
AMP DC BAL adjustment.
impedances. Unterminated connections result in reflections
in the cables and cause distortion of the displayed wave
forms.
When input signal connections are made, consider the
effect of loading upon the signal source due to the input
circuit of the Z Unit. The input resistance of the Z Unit is 1
megohm which is generally adequate to limit low-frequency
loading to a negligible value. At high frequencies, however,
the input capacitance of the Z Unit and the distributed
capacitance of cables become important. Capacitive load
ing at high frequencies may be sufficient to adversely
affect both the displayed waveform and the operation of
the signal source. Both capacitive and resistive loading
can usually be limited to negligible values through use
of attenuator probes.
Use of Probes
Attenuator probes reduce loading of the signal source.
However, in addition to providing isolation of the oscillo
scope from the signal source, an attenuator probe also de
creases the amplitude of the displayed waveform by the
attenuation factor of the probe. When making amplitude
measurements with an attenuator probe, be sure to multi
ply the observed amplitude by the attenuation of the probe.
(Additional information concerning probe attenuation will
be found under Differential Preamplifier Operation and At
tenuator Test Point portions of this section of the manual.)
An adjustable capacitor in the probe body compensates
for variations in input capacitance from one instrument to
another. To assure the accuracy of pulse and transient meas
urements, this adjustment should be checked frequently.
To make this adjustment, set the oscilloscope calibrator
controls for a calibrator output signal of suitable amplitude.
Touch the probe tip to the calibrator-output connector and
adjust the oscilloscope controls to display several cycles
of the waveform. If the probe cable is connected to the
A input connector on the Z Unit, adjust the probe capacitor
for flat tops on the calibrator square wave. If it is connected
to the B input connector, adjust for a flat bottom on the
square wave.
Conventional Preamplifier Operation
When the Z Unit is used for conventional preamplifier
operation, the Mode switch should be placed in either
the A ONLY or the —B ONLY position. Input signals should
then be connected to the corresponding input connector.
Operation of the unit in the two positions is essentially the
same except that signals applied to the B input connector
are inverted on the display. Positive voltages produce an
upward deflection when applied to the A input connector
and a downward deflection when applied to the B input
connector (see Fig. 2-3).
Fig. 2-3. W aveform s applied to the A Input connector produce an
upright display, while waveforms applied to the B Input are in
verted.
The amount of vertical deflection produced by a signal
is determined by the settings of the VAR. ATTEN. control
and the VOLTS/CM switch. Calibrated deflection factors
indicated by the settings of the VOLTS/CM switch apply
only when the VAR. ATTEN. control is set fully clockwise.
Serious errors in display measurements may result if the
setting of this control is inadvertently moved away from
the fully clockwise position.
The range of the VAR. ATTEN. control is approximately
2.5 to 1 to provide continuously variable (uncalibrated)
vertical-deflection factors between calibrated settings of
the VOLTS/CM switches.
Voltage measurements may be made directly from the
oscilloscope screen by noting the deflection factor on the
appropriate VOLTS/CM switch dial, and the amount of
deflection on the screen. Then multiply the deflection on
the screen by the setting of the VOLTS/CM switch and the
attenuation factor, if any, of the probe.
Placing the AC-DC switch in the AC position inserts a dc
blocking capacitor in series with the input circuit. In the
AC position, the input time constant is 0.1 second and the
low-frequency response is —3 db at 2 cps. Thus some
attenuation exists even at 0 cps. Because the input dc
signal may be suppressed by means of the calibrated com
parison voltage feature, there are few occasions where the
ac-coupling mode will be needed. Two principle occasions
are: (1) When it is desired to get a quick look at the ac
component of a signal which has a large dc component
and (2) where there is a difference in dc levels of the two
signals to be observed during differential mode of operation.
The tolerances of the input circuit time constants (at
—3 db frequency) are nominally =h2%. When tighter
®T 2-3
http //manoman.sqhill.com

Operating Instructions — Type Z
matching between A and B input circuits is necessary, one
input dc blocking capacitor may be “ padded" with a small
additional capacitance, generally less than 0.001 /ifd.
The PUSH TO DISCONNECT SIGNAL buttons allow the
signal to be momentarily removed from the input without
the bother of disconnecting the probe or coaxial input con
nector. This provides an easy method for finding the base
line of zero voltage level on the crt. (When utmost ac
curacy in measurement is required, trace deviation from
exact zero due to gas or grid current must be considered.)
The POSITION control may then be adjusted to make the
zero level lie at any graticule mark desired.
Differential Preamplifier Operation
The primary purpose of differential operation is to elim
inate undesirable common-mode signals. The term “common-
mode signal" is defined as that signal which is common
to both inputs of a differential amplifier. It most commonly,
but not necessarily, represents unwanted hum or noise.
This feature can be used, for example, to observe the
signal across one circuit element while effectively eliminat
ing the remainder of the circuit from the observations. Tnis
is accomplished by connecting the signal at one end of
the element to one input of the Z Unit and the signal at
the other end of the element to the other input of the unit
Differential operation between the two inputs is obtained
when the Mode switch is in the A-B DIFF. position. Maximum
common-mode rejection is obtained when both input at
tenuators are set to XI. Common-mode rejection is a func
tion of frequency in practical amplifiers. It is 40,000 to 1
for dc common-mode signals in the Z Unit and remains
near that value through audio frequencies, decreasing as
the frequency increases.
The differential or common-mode rejection ratio of the
Z Unit describes the ability of the unit to reject common
mode signals. Common-mode rejection ratio is best defined
as the ratio of amplifier response to that part of the input
signal not common to both, with respect to the response
of the amplifier to any input signal which is common to
both inputs. It is defined numerically in the following ex
ample.
If an input signal consists of 100 volts (p-p) of 0-cps hum
and 0.1 volt of desired signal, the 100-volt hum would cause
-nr ---- ;—7 ------- times 100 volts or 2000 cm of deflection, and
.05 volts/cm
the signal would cause an additional 2 cm of deflection.
If conventional preamplifier operation were used, the de
sired signal would be deflected off the screen and could
not be observed. However, if differential operation is
used and common-mode rejection were 2000 to 2 or
1000 to 1, then the hum and desired signal would each
produce 2 cm of deflection. The resulting combined wave-
ir s r
i
/
/
la) 100-volt, 60~hum plus 0.1-volt, 1-kc square
wave. Vertical Sensitivity 25 v/cm. Mode A ONIY.
Sweep Rate 5 miliisec/cm.
7 r 7
,V
L
j
\/V/
\
u.
V /
(c) 100-volt 60— hum only. Control settings similar
to (a) except Mode is — B ONLY.
(b) Top 4-cm of waveform (a) at vertical sensitivity
of 0.05 v/cm. Mode A-Vc, decoupled. VcSi + S v.
Sweep Rate 0.5 millisec/cm.
++++ 4+B ++++ t+H W+ H ++ +-H4 ++++ m + ++++
id) 60— hum is differentially suppressed and only the
1-kc square wave is displayed. Vertical Sensitivity
0.05 v/cm. Mode A-B DIFF., dc-coupled. Sweep Rate
0.5 millisec/cm.
2-4
Fig. 2-4. Common-mode rejection by the Z Unit.

Operating Instructions — Type Z
form could be seen but not easily measured. With a
common-mode rejection of 40,000 to 1, the hum would be
reduced to 0.5 mm and the desired signal alone could be
accurately observed and measured.
The preceding example is shown pictorially in the series
of waveform photographs shown in Figs. 2-4(a), (c), and (d).
A combined 100-volt hum and 0.1-volt square-wave signal
is shown in Fig. 2-4(a). Although the square wave does
not seem to be present, it can be made visible by increasing
the sensitivity of the Z Unit to 0.05 volts/cm, which increases
the effective height of the waveform to 2000 cm. A dc com
parison voltage (using differential comparator operation
explained later in this section) of approximately 50 volts
is used to bring the top 4-cm portion of the combined
signals into view, shown by the waveform photograph in
Fig. 2-4(b). The 2-cm high square-wave signal, riding on
top of the hum but not synchronized with it, causes the
separated appearance of the hum signal. Fig. 2-4(c) shows
the 100-volt (p-p) hum signal which, by itself, is applied to
the B input connector. The resulting display using common
mode rejection is shown in Fig. 2-4(d).
The following five operational notes provide helpful in
formation to obtain optimum performance from the Z Unit
using this mode of operation.
1. Large signal response of the Z Unit as a differential am
plifier is shown in Table 2-1.
TABLE 2-1
Signal Handling Capabilities of the Z Unit
Attenua
tion Maximum Calibrated
Sensitivity
(volts/cm)
Minimum
Uncalibrated
Sensitivity
(volts/cm)
Maximum
Signal or
Common
Mode
(volts)
Magni ■
fication
Factor
XI .05 .12 100 2000X
X2 .1 .24 200 1000X
X5 .25 . 500 400X
X10 .5 1.2 1000* 200X
X20 12.4 1000* 100X
X50 2.5 1000* 40X
XI00 512 1000* 20X
fox
X200 10 24 1000*
X500 25 0 1000* 5X
^Maximum continuous dc input level with AC-DC switch set to DC: 800
volts; momentary maximum dc level should not exceed 1000 volts.
2. Any difference in attenuation factors of the two attenua
tors (VOLTS/CM switches) will decrease the differential
capabilities of the Z Unit to the extent shown in Table 2-2.
3. Both AC-DC switches should be in the DC position if
possible as explained under Conventional Preamplifier
Operation.
4. Differential balance may decrease slightly as the VAR.
ATTEN. control is adjusted away from the calibrated
(clockwise) position.
5. Either input signal alone may be viewed without switch
ing back to the A ONLY or —B ONLY positions of the
Mode switch by depressing the PUSH TO DISCONNECT
SIGNAL button of the other input channel.
TABLE 2-2
Attenuator Performance
Attenuation Attenuator
Accuracy, ± % Input Resistance
Tolerance, ± %
XI 0 1
X2 11
X5 1.5 1
X10 and up 2 1
If conventional probe is used, the probe resistor tolerance of 1 % de
creases the Z Unit attenuator accuracy. These inaccuracies can be ac
curately measured as explained later under Attenuator Test Point.
Calibrated Differential Comparator Operation
When the Mode switch is in the A-Vc or Vc-B position,
the Z Unit is a calibrated differential comparator or slide-
back voltmeter. The calibrated comparison voltage, which
has a range of 0 to 100 volts, may be added (differentially)
to either input signal.
In this mode a calibrated dc voltage is internally applied
to cancel out any unwanted dc component in the applied
signal, thereby allowing accurate measurements of relative
ly small ac signals riding on top of relatively large dc
signals.
When the Mode switch is in the A-Vc position, the com
parison voltage is applied internally to the amplifier input
where the B signal is ordinarily applied during differential
mode of operation. The switches and input connector in
the —B ONLY section of the front panel are not used.
Signals applied to the B input connector will not be ob
served.
In Vc-B position of the Mode switch, the comparison
voltage is applied to the amplifier input where the A input
signal is normally applied during differential mode of op
eration. All switches and the input connector in the A ONLY
section of the front panel are not used.
The dc comparison voltage is set by 3 controls: the COM
PARISON VOLTAGE Polarity, Range, and Helidial. The
Range control has ranges of 0 to 1, 0 to 10, and 0 to 100
volts. The Helidial varies the comparison voltages over
this range and indicates the precise comparison voltage at
any particular setting.
NOTE
The regulator circuit in the Z Unit maintains con
stant, accurate, comparison voltages as long as
the oscilloscope — 150- and + 225-volt power
supplies are in regulation and within their output
voltage tolerance ratings. Be sure these and other
regulated power supplies in the oscilloscope are
operating properly.
Differential comparator mode of operation may be used
to make the following voltage measurements: (1) dc volt
age measurements, (2) ac signal measurements superimposed
on dc, and (3) high-amplitude ac signal measurements.
2-5

Operating Instructions — Type Z
1. DC Voltage Measurements.
When the Z Unit is used to make any dc voltage measure
ments, it is first necessary to establish a reference line on
the screen of the oscilloscope. This line will usually be the
horizontal centerline of the graticule. To establish the
reference, set the COMPARISON VOLTAGE Polarity switch
to 0 and press the appropriate PUSH TO DISCONNECT
SIGNAL button to disconnect the input signal. (As noted
previously under Conventional Preamplifier Operation, slight
trace deviation from exact zero must be taken into account
to obtain best accuracy.) Use the POSITION control to
set the oscilloscope trace at the centerline of the graticule.
To measure a dc voltage component of ±100 volts or less,
apply the input signal to one of the connectors. For ex
ample, suppose the signal is applied to the A input
connector, then proceed as follows:
(a) Place the A VOLTS/CM switch to .05 and the Mode
switch to the A-Vc position.
(b) If the dc voltage component to be measured is posi
tive, place the COMPARISON VOLTAGE Polarity switch to
the + position. If it is between 10 and 100 volts, set the
COMPARISON VOLTAGE Range switch to 100 V.
(c) Rotate the COMPARISON VOLTAGE Helidial to bring
the desired portion of the trace onto the screen. Set the
trace exactly on the reference line with the Helidial.
(d) Recheck the reference as described in the first para
graph.
(e) When the zero reference line and signal trace appeiar
at the same place on the screen, the input voltage and
the comparison voltage are equal.
2. AC Signal Measurements Superimposed on DC
Small ac signals superimposed on a dc component can
be measured accurately by first using the comparison volt
age to effectively eliminate the dc component. The ac
signal can then be measured in the same manner as in con
ventional preamplifier operation. The VAR. ATTEN. control
must be kept clockwise to obtain correct results.
3. High-Amplitude AC Signal Measurements.
High-amplitude ac signals, subject to the rise rate and fall
rate limitations listed in the Specifications section, can also
be measured with the Z Unit at maximum sensitivity. This
type of measurement is very similar to dc measurements
except that it is not necessary to establish a zero voltage
reference line unless measurements of both ac and dc volt
age levels are to be made. To measure the voltage differ
ence between two points on the waveform, proceed as fol
lows:
(a) Set the Helidial to zero and position one point on the
waveform to the horizontal centerline of the graticule.
(b) Use the Helidial and Range controls to bring the other
desired point to the centerline.
(c) The voltage difference between the two points is
read from the Helidial and the setting of the Range switch.
AC-DC Voltage Measurements Exceeding ± 10 0
Volts.
If ac, dc, or both ac and dc voltage components are
greater than ±100 volts, the .05 settings of the VOLTS/CM
switches cannot be used. It will be necessary to use a lower
sensitivity in order to prevent overdriving the preamplifier
and to prevent exceeding the comparison voltage available.
To obtain the correct voltage measurement, use the multi
plication factor which appears below the volts per centi
meter setting on the VOLTS/CM knob. The product of the
multiplication factor times the comparison voltage used
is the input signal voltage.
ATTENUATOR TEST POINT
Two applications included here show how the ATTEN
TEST PT connector, located on the left side of the Z Unit,
can be used to make attenuation factor or ratio checks on
probes used with the Z Unit and on the internal attenuators
of the unit. The test point, when connected to a voltage
divider network under test, forms a bridge circuit as shown
in Fig. 2-5. The crt is the null indicator and the Helidial
reading is used to determine the attenuation factor or ratio
of the divider resistors.
A third application describes how the unit may be used
to measure external resistors.
± 100 V
Fig. 2-5. Sim plified diagram of the bridge circuit formed during
use of the ATTEN TEST PT connector.
2-6

Operating Instructions — Type Z
Checking Attenuation Accuracy of VOLTS/CM
Switches
The attenuation accuracy of the X2, X5, XI0, and X20
positions of the VOLTS/CM switches can be determined by
utilizing the 100-volt comparison voltage available at the
ATTEN TEST PT connector. The following procedure ex
plains how to check the X2 position of the A VOLTS/CM
switch. The other positions are checked in the same manner,
1. Set the A VOLTS/CM switch to X2, the AC-DC switch to
DC, and the Mode switch to A-Vc.
2. Place the COMPARISON VOLTAGE Polarity switch to 0
and position a free-running trace to the center of the screen
for reference,
3. Remove the left side panel from the oscilloscope. Connect
a test lead from the A input connector to the ATTEN TEST
PT connector (see Fig. 2- ).
Fig. 2- . Left side view of the Z Unit showing the location of the
ATTEN TEST PT.
CAUTION
Use care in making the test lead connections to
prevent shorting the 100 volts at the ATTEN TEST
PT to ground. An accidental short circuit may
damage the CAL. 4 adjustment (R7 84).
4. Set the COMPARISON VOLTAGE Polarity switch to +
and the Range switch to 100 V.
5. Rotate the Helidial to return the trace to the reference
level obtained in step 2. Use the vertical trace indicator
lights to aid in returning the trace. In this example the
Helidial should end up in the vicinity of 5.00 (or 50 volts).
. Divide the Helidial reading into 10 to obtain the at
tenuation factor. (Assume the Helidial reading to be 5.02.
5.02 divided into 10 is 1,99 or an attenuation factor of XI.99.
The attenuation ratio is 1.99 to 1).
Checking Attenuation Accuracy of Probes
Passive attenuator probes can be checked for attenuation
accuracy by a method similar to that used for determining
the VOLTS/CM attenuation accuracy. Referring to Fig. 2-5,
divider resistor R1 is the 1-meg input resistor in the oscil
loscope, R2 is the resistor in the probe. The procedure which
follows describes a method for checking a 10X attenuator
probe.
1. Set the A VOLTS/CM switch to XI, the AC-DC switch to
DC, and the Mode switch to A-Vc.
2. Place the COMPARISON VOLTAGE Polarity switch to 0
and position a free-running trace to the center of the screen
for reference.
3. Remove the left side panel from the oscilloscope [if not
already removed). Connect the probe cable connector to
the A Input connector on the Z Unit and connect the probe
tip to the ATTEN TEST PT.
4. Set the COMPARISON VOLTAGE Polarity switch to -j-
and the Range switch to 100 V,
5. Rotate the Helidial to return the trace to the reference
level obtained in step 2. In this example the Helidial should
end up near a reading of 10 volts,
. Divide the Helidial reading into 100 to obtain the at
tenuation factor of the probe.
Checking External Resistors
External resistors can be checked for value against the
1-megohm input resistance of the unit by using the bridge
circuit of Fig, 2-5. In this application, R2 is the resistance
to be measured and R1 is the internal 1-megohm resistor.
The following procedure can be used:
1. Set the A VOLTS/CM switch to XI, the AC-DC switch to
DC, and the Mode switch to A-Vc.
2. Place the COMPARISON VOLTAGE switches to 0 and
100 V. Position a free-running trace to the center of the
screen for reference.
3. Remove the left side panel of the oscilloscope. Connect
one end of R2 to the A input connector and the other end
to the ATTEN TEST PT (see Fig. 2- ) by using a jumper
wire.
4. Set the COMPARISON VOLTAGE Polarity switch to -f.
5. Adjust the Helidial to return the trace to the reference
level obtained in step 2. Use the vertical trace indicator
lights to aid you in returning the trace.
6. Let H be the Helidial reading. Then use the folowing
equation to find the value of R2.
R2 = R1 1 ^ - = — ^ Megohms.
If R2 is small compared to 1 megohm, the Helidial read
ing will be very close to 10,00 making it difficult to obtain
an accurate measurement. When this occurs, R1 can be
shunted by an accurate external resistor which will permit
Helidial readings around 5.00. The only restriction on the
shunting is that the total resistance to ground from the
ATTEN TEST PT should not be less than 20 k. This limits the
current drawn from the test point to a maximum of 5 ma. If
the 1-megohm resistor is shunted, R1 in the equation will
have to be changed to the new value of the 1-megohm
and shunt resistors in parallel.
@1 2-7
http //manoman.sqhill.com

A
INPUT
t
B
INPUT
r
■»

OUTPUT
1
1OUTPUT
1 .. CATHODE
Q7644 1
*
FOLLOWER
1
1V7663A
1
1
OUTPUT AMPLIFIER
STAGE
OUTPUT
AMPLIFIER
1
1
1 ,
OUTPUT
CATHODE
Q8644 1
1
1
FOLLOWER
V7663B
OUTPUT CATHODE
FOLLOWER STAGE
PIN 1
O
£i§
o
u
PIN 3
•OUTPUT
O
i
CO
Fig. 3-1. Type
Z
Plug-In Unit block diagram.

BLOCK DIAGRAM DESCRIPTION
SECTION 3
CIRCUIT
DESCRIPTION
DETAILED CIRCUIT DESCRIPTION
Fig. 3-1 shows the block diagram for the Type Z Unit.
Signals applied to A Input and B Input connectors pass
through the VOLTS/CM Attenuator switches to the grids
of the tubes in the Input Cathode Follower stage. The
VOLTS/CM switches insert frequency-compensated attenu
ators into the circuit. When properly adjusted the input
resistance and capacitance of the unit remains unchanged
as the attenuators are inserted.
Accurate ±DC comparison voltages are obtained from
the Comparison Voltage Regulator. These can be applied to
the grid of either Input Cathode Follower stage by means of
a Mode switch. These voltages add differentially to the
signal applied to the other Input Cathode Follower when
differential-comparator mode of operation is used.
The low-capacitance, high-impedance input of the Cath
ode Follower stage isolates the input circuitry from the
amplifier stages. The Input Cathode Followers are required
to handle input signal voltages as great as ±100 volts,
without distorting. Special Constant-Current circuits prevent
the cathode followers from cutting off or drawing grid
current with large signals. Screen Voltage Regulator circuits
maintain a constant voltage between the cathode and
screen grid of the cathode followers. The Constant-Current
and Screen-Regulator circuits permit the cathode followers
to handle large signals without operating nonlinearly.
The output of the Input Cathode Followers is applied to
the control grids of the Differential Amplifier stage. This
stage also employs a Constant-Current circuit and a screen
Voltage Regulator to permit the stage to handle large signals
without distortion.
The output of the Differential Amplifier stage is applied
to the bases of the transistors in the Output Amplifier stage
Signals from the Output Amplifier stage are applied
through voltage dividers to the Output Cathode Follower
stage. The voltage dividers provide the proper dc operating
voltages at the grids of the Output Cathode Follower stage.
Output signals from this stage are then applied to the in put
of the oscilloscope main vertical amplifier through pins
1 and 3 of the interconnecting plug. Overall gain of ihe
preamplifier is 2, push-pull.
You may wish to refer to the schematic diagram located
near the rear of the manual and the block diagram of
Fig. 3-1 during the following discussion.
Comparison Voltage Regulator
Regulation of both the + and — comparison voltages
is necessary to maintain specified voltage accuracy. This
regulation system makes the comparison voltage independent
of differences in regulated power supply voltages from one
oscilloscope to another.
The comparison voltage is developed across V7 89, a
highly stable gas tube, type OG3. Because the drop across
the tube is less than 100 volts, three zener diodes are placed
in series to increase the reference voltage to slightly more
than 100 volts. In addition to increasing the total voltage
drop in the circuit, the zener diodes provide temperature
compensation for V7 89.
A constant-current source of ma is required to maintain
a constant voltage across the gas tube, V7 89. For the
— 100-volt comparison voltage reference the ma is pro
vided by a constant-current transistor, Q8 74, which operates
as a common-base amplifier. The base voltage is estab
lished with respect to the —150-volt supply by zener diode
D8 79. Since the base-to-emitter voltage of Q8 74 is es
sentially constant, the current through the transistor is de
termined and maintained constant by the voltage across
resistors R8 73 and R8 74. By adjusting R8 74, the current
through V7 89 is set to the specified ma. Transistor
Q8 72, a diode-operated 2N1102, provides temperature
compensation for Q8 74.
For the + 100-volt reference, a constant current of ma
is furnished by Q7 74 in conjunction with zener diode D7 75
and resistors R7 70 and R7 71. This circuit operates similar
to the —100-volt reference previously explained.
As the COMPARISON VOLTAGE Polarity switch is moved
from + position to — position, it is important that the load
on transistors Q8 74 and Q7 74 remain the same. In the
+ and 0 positions, the current from the negative current
regulator, Q8 74, passes through R8 70 instead of the gas
tube and associated zener diodes. In the — position, the
current from the positive current regulator, Q7 74, passes
through R8 70. In calibration, the voltage at Test Point A
is set equal to the voltage at Test Point B in all positions
of the polarity switch, so that a constant load is always pre
sented to Q7 74 and Q8 74. The voltage is then applied
across the COMPARISON VOLTAGE potentiometer, R7 8 .
The voltage applied across potentiometer R7 8 must
be exactly 100 volts. Since the voltage obtained by the
3-1

Circuit Description — Type Z
drop across V7 89 and the zener diodes is slightly more
than 100 volts, R7 84 and R7 85 (if needed) reduce the
potential to the exact amount required.
The precision voltage dividers consisting of R7 87A and
R7 87B (XI0), and R7 87C and R7 87D (XI00), reduce the
comparison voltage from 100 volts to either 10 volts or
1 volt by means of the COMPARISON VOLTAGE Range
switch.
Input Cathode Follower Stage
Signals applied to input connectors A and B of the Type
Z Unit go to the AC-DC switches which either include,
or short across, the coupling capacitors. The signals then
pass through the PUSH TO DISCONNECT SIGNAL switches,
the VOLTS/CM switches, and the Mode switch, SW7 11.
The signals are then impressed upon the grids of the input
cathode followers, V7 13 and V8 13.
The wide dynamic range of the Type Z Unit requires
constant-current operation of both the Input Cathode Pol-
lower stage and the Differential Amplifier stage. Another
requirement is that screen-to-cathode voltages remain con
stant in both stages. Transistor Q7 18 is the constant-current
source for both V7 18A and input cathode follower V7 13.
This transistor operates as a common-base amplifier. Its
base is held approximately volts above the -150-volt
supply by zener diode D8 79 (see Note, below).
NOTE
When reference to the — 150-volt supply is made,
the actual typical voltage measurement is — 144
volts at pin 9 of the interconnecting plug in all
oscilloscopes using a decoupling network in the
main oscilloscope.
The base-to-emitter voltage is essentially constant, the
base being a few tenths of a volt more positive. With base
and emitter voltages fixed, Q7 18 operates at a constant
current. Note that a variation in the -150-volt supply has
little or no effect on the transistor bias. Thus no change oc
curs in either the base-to-supply drop or the base-to-emitter
drop. Only the base-to-collector drop varies.
The voltage drop across zener diode D8 79 sets the
voltage drop between emitter and the —150-volt supply.
A decrease in emitter resistance would require a greater
current to establish the same fixed drop. Hence R7 19 is
the current control for Q7 18, the constant-current source.
The collector current of Q7 18 is slightly less than the
emitter current, very nearly constant, and independent of
the base-to-collector voltage. Such a circuit is very staole
with respect to transistor parameters and temperature.
To describe the constant-current circuit of the Inout
Cathode Follower stage during peak operation, assume
that an input voltage swing from —100 to +100 volts is
applied to the grid of V7 13. The cathode of V7 13 end
plate of V7 18A follow the 200-volt swing. The cathcde
of V7 18A varies --------- — times the plate swing. In this
H + 1
circuit, the cathode swings about 1/30 of the plate swing.
Therefore the grid-cathode swing of V7 18A is approxi
mately 6.6 volts. The voltage swing is now low enough
for direct coupling to the collector of Q7 18 whose func
tion is to provide the constant-current source for this half
of the input stage. The voltage swing of 6.6 volts is easily
handled by the transistor at its operating current of ap
proximately 8 ma.
The effect of a transistor “long-tail” in the cathode circuit
of V7 18A is shown in Fig. 3-2. The top curve displays
the constant-current characteristics of a 2N1302 transistor
when connected similar to Q7 18. The lower curve displays
the constant-current characteristics of V7 18A with Q7 18
connected in its cathode circuit to control the current. For
practical purposes, no measurable change in current occurs
during these voltage excursions.
The grid of V7 18A returns to the zener diode D8 79
through a temperature-compensating diode-connected tran-
'c
1 ma/div
P
1 ma/div
1 volt/div
20 volti/div
Fig. 3-2. Top: constant-current collector characteristics of 2N1302
transistor having a 1-k resistor in the emitter circuit; bottom : con
stant-current plate characteristics of DJ8 triode connected similar to
V7 18A. {Transistor display obtained from Tektronix Type 575
Transistor-Curve Tracer; triode display obtained from Type 570
Characteristic-Curve Tracer.)
3-2

Circuit Description — Type Z
sistor, Q8 72. The bias of V7 18A is the collector-to-base
voltage of Q7 18 plus the drop across Q8 72.
The screen of the input cathode follower V7 13 is con
nected back to its cathode through another cathode fol
lower, V7 23A, and zener diode, D7 21. The screen
voltage of V7 13 will therefore follow variations in the
cathode voltage (because it is “bootstrapped" to the
cathode), approximately 105 volts above the cathode.
Capacitor C7 2 bypasses high-frequency components of
the signal directly to the screen. C7 21 and R7 22 form
a low-pass filter to remove zener noise from the screen
of V7 13.
The gain of the input CF's (V7 13 and V8 13 approaches
unity because the impedance of the constant-current cathode
“long-tail" approaches infinity, and because of the high
and constant grid-screen p. The grid-screen p remains
constant because of the constant screen-cathode potential.
The most significant factor which reduces the gain of the
stage below unity is the cathode-load resistors R7 20,
R7 21, and R8 21.
Slight circuit imbalances, principally in triode p and
zener diode impedance, necessitate a balance control
R7 20. For all practical purposes, this control, plus R7 21
and R8 21, form the cathode load for the input cathode
followers.
Differential Amplifier Stage
Signals from the input cathode followers are applied to
the grids of the Differential Amplifier stage, V7 34 and
V8 34. The cathode circuitry of the stage consists of a
constant-current circuit and a gain adjustment network.
The constant-current circuit is formed by Q8 38 and V8o38
and is identical in principle, with one exception, to the
operation of the circuits in the Input Cathode Follower
stage. The exception is that one constant-current circuit
supplies both tubes in this stage.
The amount of current supplied by the constant-current
circuit is determined by the setting of the GAIN ADJUST
control R8 39. As screen-to-cathode voltage is maintained
constant, R8 39 controls the transconductance of V7 34 and
V8 34, thereby controlling the gain of the stage. The
control is set to provide the correct vertical deflection fac
tors when the VAR. ATTEN. control R7 33 is set fully clock
wise. The VAR. ATTEN. control varies the gain of the Dif
ferential Amplifier stage by varying the cathode degenera
tion.
To prevent trace shift as the VAR. ATTEN. control R7 33
is adjusted, the cathode potentials must remain equal. This
is accomplished by proper adjustment of the VAR. ATTEN.
BALANCE control R7 19. Adjustment of R7 19 varies the
grid (and the cathode) voltage of V7 34 and V8 34 in
opposite directions to compensate for slight differences in
operating characteristics of the two tubes. Proper adjust
ment of R7 19 will result in equal voltages at the cathodes
of V7 34 and V8 34 for all positions of the VAR. ATTEIN.
controls.
As in the Input Cathode Follower stage, the screen volt
age for the Differential Amplifier stage is “bootstrapped"
140 volts above the cathode. Because total cathode current,
screen-to-cathode voltage, and the plate-to-screen current
ratio remain constant, the plate currents of the Differential
Amplifier stage respond only to differential signals.
The high-frequency response of the Differential Amplifier
stage is improved by the use of series-shunt peaking in the
plate circuits. This peaking is provided by L7 32 and
L8 32.
The AMPLIFIER DC BAL. control R7 40 adjusts the base
voltage of Q7 44 by forcing a small current through R7 32.
The control is used to dc balance the Output Amplifier
Stage. Adjustment of R7 40 forces the base of Q7 44 to be
at the same voltage as the base of Q8 44 when no signal
is applied to the unit.
Output Amplifier Stage
Output signals from the Differential Amplifier stage are
applied to the bases of Q7644 and Q8 44, the Output
Amplifier stage. This stage has a gain of slightly more than
two. A large common emitter resistance provides a large
amount of emitter degeneration and a high degree of
stability and linearity. Transistors used in this stage have
an advantage over a vacuum tube stage in two respects.
The dc level is lowered instead of raised, and the swing
of the amplifier in the oscilloscope is limited to no more
than 12 centimeters deflection on the crt screen. The latter
is important since rapid recovery from very large input
voltages is essential. Series-shunt peaking in the collector
circuit improves the high-frequency response of the ampli
fier.
Output Cathode Follower Stage
Output signals from the Output Amplifier stage and
positioning voltages from the POSITION control are ap
plied to the grid circuits of the Output Cathode Followers.
Compensated voltage divider networks at the input to the
cathode followers lower dc levels to the proper level for
driving the vertical amplifier of the oscilloscope. The divid
ers consist of resistors R7 55 and R7 5 , R8 55 and R8 5 ;
capacitors C7 55 and C8 55 compensate the attenuators
for high frequencies.
The OUTPUT CF BAL. adjustment R7 58 is used to pro
vide dc balance for the output cathode followers. This
insures that the input signals to the push-pull sides of the
vertical amplifier of the oscilloscope are at equal average
dc potentials.
The output cathode followers provide the necessary low
impedance to drive the capacitance of the interconnecting
plug and the input of the oscilloscope vertical amplifier.
In addition, this stage isolates the plug capacitance from
the Output Amplifer stage. The signal from the Output
Cathode Follower stage is applied through the intercon
necting plug to the input of the oscilloscope vertical ampli
fier.
3-3

ON 4
The Z Unit is a stable instrument, and will require com
plete calibration very infrequently. However, to be certain
that the unit is operating properly at all times, the cali
bration of the unit should be checked after each 500-hour
period of operation (or every six months if the unit is used
intermittently). A complete step-by-step procedure for cali
brating the unit and checking its operation is given in the
Calibration section of this manual.
Visual Inspection
Many potential and existent troubles can be detected by
a visual inspection of the unit. For this reason, a complete
visual check should be performed every time the unit is
inoperative, needs repairs, or needs recalibration. Apparent
defects may include loose or broken connections, damaged
connectors, improperly seated tubes or transistors, scorched
or burned parts, and broken terminal strips. The remedy
for these troubles is readily apparent except in the case
of heat-damaged parts. Damage to parts due to heat is
often the result of other less apparent troubles in the unit.
It is essential that the cause of overheating be found before
replacing the damaged parts.
COMPONENT REPLACEMENT
General
Useful information concerning the replacement of im
portant parts in the Z Unit is given in this portion of the
manual. Because of its precision design, replacement of
close tolerance components will require calibration of the
unit to assure proper operation. Refer to the Calibration
section of this manual for a complete procedure. If the
steps in the procedure are to be performed out of sequence
to get the repaired portion of the Z Unit calibrated, refer
to the preceding portion of the procedure for more infor
mation about control panel settings and test equipment
used.
Switches
If a switch is found to be defective and needs to be
repaired or replaced, use normal care in unsoldering and
MAINTENANCE
disconnecting leads from the terminals. To remove some
switches, such as the AC-DC, Polarity, and Range, the
front overlay panel must be removed first to obtain access
to the switch mounting screws.
Single wafers on wafer-type switches are not normally
replaced. If a wafer is defective, the entire switch should
be replaced. Some switches may be ordered from the
factory either unwired or with parts wired in place, as de
sired. Refer to the Parts List to find the wired and unwired
part numbers.
When soldering the leads to a wafer-type switch, do not
let solder flow around and beyond the rivet on the switch
terminal. Otherwise the spring tension of the switch con
tact may be destroyed.
Turret Attenuators
To remove or to replace a component inside one of the
VOLTS/CM turret attenuators, the following instructions are
given:
1. To remove the turret, loosen the 0.050" alien set screw
(see Fig. 4-1). Grasp the knob and pull it outward far
enough to let the shaft free the turret. Do not pull the
shaft too far out or it will not hold the detent wheel in
position.
2. Remove the turret. Remove the end caps from the body
of the turret to obtain access to the components.
NOTE
When replacing any of the components inside the
turret, the lead lengths and parts placement are
critical. Duplicate the original lead lengths and
the exact part placement. Use parts ordered from
the factory to assure correct physical size and
tolerance accuracy. Do not use excessive heat or
let the soldering iron touch the white plastic part
of the turret body. No attempt should be made
to replace button capacitors C413E, C414E, or
C415E. These parts are sweat-soldered in the
outer metal ring to secure a low inductance
grounding path. The ring is fitted to the body
of the turret before the inside components are
soldered into place. It is extremely unlikely that
these capacitors will become defective. How
ever, if a button capacitor needs to be replaced,
order a replacement wired turret body from the
factory.
4-1

Maintenance — Type Z
THRUST SPRING
(Shown rotated
FRAME CONTACTS 180° ,rom e0,r,“
Fig. 4-1. B VOLTS/CM turret attenuator removed from the Z Unit.
3. To remount the turret body, align the holes in the end
caps with the index pins. Fit the end caps to the turret
body.
4. Note the setting of the knob and then rotate the knob
so the bent ends rather than the open ends of the thrust
spring will accept the turret.
5. Slide the turret into the frame. Make sure the contacts
(indicated in Fig. 4-1) are aligned with the contacts on the
turret.
. Rotate the knob to its original setting. Slide the shaft
through the turret and through the rear hole in the frame.
Check alignment of contacts while carefully rotating the
turret. Tighten the set screw.
7. If the bent ends of the thrust spring are not located
between the roll pins, rotate the thrust spring around the
shaft until it is properly positioned. When this is done,
the bent ends of the spring will not strike the detent wheel
stop as the turret is rotated.
If the entire VOLTS/CM turret attenuator is to be re
moved or replaced, the complete switch can be removed
as a unit the same as a conventional rotary switch. When
ordering a replacement switch, refer to the Parts List lor
the wired switch part number.
Ceramic Terminal Strips
Damaged ceramic terminal strips are most easily removed
by unsoldering all connections and then using a plasric
or hard rubber mallet to knock the yokes out of the chassis.
This can be done by tapping on the ends of the yokes
protruding through the chassis. When a new strip is
ordered, the yokes are furnished with and are attached
to the strip. New spacers need not be ordered because
the original spacers can be used two or three times before
they become too loose to hold the yokes securely.
When the damaged strip and yoke assembly have been
removed, place the spacers for the new strip assembly
into the holes in the chassis. Using a plastic or hard rubber
mallet, tap the ceramic strip lightly above the yokes to
drive the yoke pins down through the spacers. Be certain
that the yoke pins are driven completely through. Using
a pair of diagonal cutters, cut off the excess length of the
yoke pins. Fig. 4-2 illustrates the way that the parts fit
together.
Ceramic Strip Yoke
Chassis Spacer Yoke Pin
4-2
Fig. 4-2. Installation of ceramic term inal strips.