Tektronix 176 User manual

Tektronix, Inc.
P.O.
Box 500
Beaverton, Oregon 97077
070-1073-00
Product Group 48
COMMITTED TO EXCELLENCE
PLEASE CHECK FOR CHANGE INFORMATION
AT THE REAR OF THIS MANUAL.
176
PULSED HIGH
CURRENT
FIXTURE
INSTRUCTION MANUAL
Serial Number _____ _
First Printing OCT 1970
Revised JAN 1983

Copyright .i 1970 Tektronix, Inc. All rights reserved.
Contents of this publication may not
be reproduced in any
form without the written permission of Tektronix, Inc.
Products of Tektronix, Inc. and its subsidiaries are covered
by U.S. and foreign patents and/or pending patents.
~
TEKTRONIX, TEK, SCOPE-MOBILE, and ~ are
registered trademarks of Tektronix, Inc. TELEQUIPMENT
is a registered trademark of Tektronix U.K. Limited.
Printed
in U.S.A. Specification and price change privileges
are reserved.
INSTRUMENT SERIAL NUMBERS
Each instrument has a serial number on a par'lel insert, tag,
or stamped
on the chassis. The first number or letter
designates the country of manufacture. The last five digits
of the serial number are assigned sequentially and are
unique to each instrument. Those manufactured
in the
United States have six unique digits. The country
of
manufacture is identified as follows:
BOOOOOO
100000
200000
300000
700000
Tektronix, Inc., Beaverton, Oregon, USA
Tektronix Guernsey, Ltd., Channel Islands
Tektronix United Kingdom, Ltd., London
Sony/Tektronix, Japan
Tektronix Holland, NV, Heerenveen,
The Netherlands

176
TABLE OF CONTENTS
Page
Section 1 SPECIFICATION
Electrical Characteristics . . . . . . . .
.. 1-1
Environmental Characteristics ..
1-4
Section 2 OPERATING INSTRUCTIONS
Installation
................. .
Cooling .............. .
Controls, Indicator Lights and
2-1
2-1
Connectors . . . . . . . . . . . . . . . . . . . . . .. 2-1
General Description ......... 2-2
Effects of 176 on Type 576 Controls
.. 2-4
First Time Operation
............... 2-5
I WARNING'
THE REMAINING PORTION OF THIS TABLE OF
CONTENTS LISTS THE SERVICING INSTRUC-
TIONS. THESE SERVICING INSTRUCTIONS ARE
FOR USE BY QUALIFIED PERSONNEL ONLY. TO
AVOID ELECTRICAL SHOCK, DO NOT PERFORM
ANY SERVICING OTHER THAN THAT CALLED OUT
IN THE OPERATING INSTRUCTIONS UNLESS
QUALIFIED TO DO SO.
Section 3 MAINTENANCE
Index of Maintenance Information
3-1
Preventive Maintenance. . . . . . . . 3-2
Troubleshooting
............. 3-2
Corrective Maintenance
Obtaining Replacement Parts 3-3
Tuning the Charge
Lines. . . . 3-4
Charge Line Coil Replacement . . .
.. 3-5
Semiconductor Replacement 3-6
Relay Removal and Replacement 3-6
Pushbutton Bulb Replacement . . .
.. 3-6
Soldering on Circuit Boards 3-6
REV JAN 1982
Section 4 CIRCUIT DESCRIPTION
Block Diagram Description
Page
4-1
Circuit Description ................. 4-1
Section 5 PERFORMANCE CHECK AND ADJUST
General .......................... 5- 1
Performance Check Procedure . . . . .
.. 5-1
Adjust Procedure
.................. 5-5
Section 6 ELECTRICAL PARTS LIST
Section 7 DIAGRAMS, CIRCUIT BOARD PICTURES
AND MECHANICAL PARTS ILLUSTRATIONS
General Information
................ 7-1
Block Diagram
Circuit Diagrams and Circuit Board Pictures
Mechanical Parts Illustrations
Section 8 MECHANICAL PARTS LIST
CHANGE INFORMATION
Abbreviations and symbols used in this manual are based
on or taken directly from IEEE Standard 260 "Standard
Symbols for Units", MIL-STD-12B and other standards of
the electronics industry.

176
OPERATORS SAFETY SUMMARY
The general safety information in this part of the summary is
for both operating and servicing personnel. Specific
warnings
and cautions will be found throughout the manual
where they apply, but may not appear in this summary.
TERMS
In This Manual
CAUTION statements identify conditions or practices that
could result in damage to the equipment or other property.
WARNING statements identify conditions or practices that
could result in personal injury or loss of life.
As Marked on Equipment
CAUTION indicates a personal injury hazard not immediate-
ly accessible as one reads the marking, or a hazard to prop-
erty including the equipment itself.
DANGER indicates a personal injury hazard immediately
accessible
as one reads the marking.
SYMBOLS
In This Manual
This symbol indictes where applicable
cautionary or other information is to be found.
As Marked on Equipment
ii
~ DANGER -High voltage.
@ Protective ground (earth) terminal.
.& ATTENTION -refer to manual.
Power Source
This product is intended to operate from a power module
connected to a power source that will not apply more than
250 volts rms between the supply conductors or between
either supply conductor and ground. A protective ground
connection by way of the grounding conductor
in the power
cord
is essential for safe operation.
Grounding the Product
This product is grounded through the grounding conductor
of the power module power cord.
To avoid electrical shock,
plug the power cord into a properly wired receptacle before
connecting to the product input or output terminals. A
protective ground connection by way of the grounding con-
ductor
in the power module power cord is essential for safe
operation.
Danger Arising From Loss of Ground
Upon loss of the protective-ground connection, all
accessible conductive parts (including knobs and controls
that may appear to be insulating) can render an electric
shock.
Use the Proper Fuse
To avoid fire hazard, use only the fuse of correct type,
voltage rating and current rating as specified in the parts list
for your product.
Refer fuse replacement to qualified service personnel.
Do Not Operate in Explosive Atmospheres
To avoid explosion, do not operate this product in an explo-
sive atmosphere unless it has been specifically certified for
such operation.
Do Not Operate Without Covers
To avoid personal injury, do not operate this product
without covers or panels installed.
Do not apply power to
the plug-in
via a plug-in extender.
ADD JAN 1982

176
SERVICE SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL ONLY
Refer a/so to the preceding Operators Safety Summary.
Do Not Service Alone
Do not perform internal service or adjustment of this
product unless another person capable of rendering first
aid
and resuscitation is present.
Use Care When Servicing With Power On
Dangerous voltages may exist at several pOints in this
product.
To avoid personal injury, do not touch exposed
connections and components while power
is on.
ADD JAN 1982
Disconnect power before removing protective panels, sol-
dering, or replacing components.
Power Source
This product is intended to operate from a power source
that will not apply more than 250 volts rms between the
supply conductors or between either supply conductor and
ground. A protective ground connection by way of the
grounding conductor
in the power cord is essential for safe
operation.
iii

Fig. 1·1. 176 H igh·Current Fixture.
176

176
SECTION 1
SPECIFICA TION
The 176 Pulsed High-Current Fixture extends the testing
capability of the Type 576 Curve Tracer by providing a
pulsed collector supply output of up to 200 A peak and a
pu
Ised step generator output of up to 20 A peak. To
accomodate this increased range, the maximum peak power
output has been increased to 1000 watts and the maximum
vertical deflection factor has been increased to 20
A/division.
The 176 slides into the Type 576 in place of the
Standard Test Fixture. A set of 5 accessories jacks is avail-
able,
which accepts most Tektronix device testing acces-
sories. Kelvin sensing of collector voltage may be used for
all tests. An interlock system is used, which allows tests to
be made only when a protective box is in place over the
device under test, thus protecting users from dangerous
voltages. For remote tests, this interlock system may be
overridden
by a front panel button.
The following electrical and environmental charac-
teristics are valid
for a 176 operated in a calibrated Type
576, both instruments operated in an ambient temperature
of between O°C and +50°C.
The electrical characteristics are listed in two catagories,
performance requirements and supplementary
information.
The Performance Check and Adjust section provides a pro-
cedure
for checking the characteristics listed in the
performance requirement category. The characteristics
listed in the supplementary information category are pro-
vided
for the convenience of the user. A performance check
procedure
for the Type 576 is available in the Type 576
I nstruction Manual.
TABLE 1-1
ELECTRICAL CHARACTERISTICS
Collector Supply
Characteristic Performance Requirement Supplementary Information
Form of Output
300 f./S wide pu Ises. (80 f./S wide pu Ises
also available but performance not
specified .)
Repetition Rate Power
Line frequency
Polarity
Positive-going or negative-going as
determined by Type 576 POLARITY
switch.
Amplitude
Ranges 15, 75 and
350 volts nominal, as deter-
mined
by Type 576 MAX PEAK VOLTS
switch.
Peak Voltage
Peak open circuit voltages within +35%
and
-5% of Type 576 MAX PEAK
VOL TS switch setting for 75 and 350
positions; within +18% and -12% on
15 positions.
All at nominal line voltage.
REV JAN 1982
1-1

Specification-176
Characteristic
Peak
Current
l
Pu Ise shape
Flatness
Risetime
Falltime
Maximum Peak Power Output
Accuracy (Current steps and
offset)
Incremental accuracy
X10 STEP button not
illu minated
X10STEP button ilium-
inated,5 highest current
settings only
Absolute Accuracy
X10 STEP button not illuminated
X10 STEP button illuminated, 5
highest
current settings only
Nominal Step Amplitudes
X 10 STEP button not illuminated
X 10 STEP button illuminated, 5
highest
current settings only
TABLE 1-1 (cont)
Performance Requirement
Supplementary Information
Minimum available peak current at
low Iine into shorted load is:
200 A for 15 V range
40 A for 75 V range
8 A
for 350 V range
15V Range: Within 2% during un-
blanking interval from 20% to 100%
of maximum peak Collector Supply
voltage.
75V & 350V Range: Within 2% dur-
ing unblanking interval.
80 jlS (10% to 90%)
10 jlS (90% to 10%)
1000 watts, 100 watts or 10 watts
(Varies with line voltage).
Step
Generator
Refer to Type 576 Specification
Within 5% of 10 times Type 576
AMPLITUDE switch setting between
any
two steps without Type 576 .1 X
STEP
MUL T button pressed; within
10% of AMPLITUDE switch setting
with .1 X STEP MULT betton P""'d.
1
._---
._-
I Refer to Type 576 Specification
Within 3% of total output, plus 1% of
ten times Type 576 AMPLITUDE
switch setting, or 3% of ten times
Type 576 AMPLITUDE switch
setting, whichever is greater.
-----.------- ---
_.-
Refer to Type 576 Specification
Ten times (or one times with Type 576
.1X STEP MULT button pl'essed) Type
576 AMPLITUDE switch setting. Step
amplitude is indicated on Type 576 PER
STEP I-eadout.
I Circuit breaker in Type 576 may open up if Type 576 VARIABLE COLLECTOR SUPPLY control has been left in its clockwise position for
longer than 1/2 hour. It is advisable to leave the control in its counterclockwise position when not actually performing tests.
1-2
REV. B, APR. 1975

Specification-176
TABLE 1-1 (cont)
Characteristic Performance
Requirement Su pplementary Information
Type 576 OFFSET MUL T control
range
X10 STEP button not illuminated
Refer to Type 576 Specification
XlO STEP button illuminated, 5
Continuously variable from 0 to 100
highest current settings only
times Type 576 AMPLITUDE switch
setting, either aiding or opposing step
generator
polarity.
Maximum Current in Current Mode
(Steps and Aiding Offset)
X 10 STEP button not illuminated Refer to Type 576 Specification
X 10 STEP button illuminated
200 times Type 576 AMPLITUDE
switch setting or 20 A, whichever is
less.
Maximum Voltage in Current Mode
(Steps and Aiding Offset)
X10 STEP button not illuminated Refer to Type 576 Specification
X 10 STEP button illuminated, 5
At least 5 volts with Type 576 AM-
highest current settings only
PLiTUDE switch set to 10 rnA, 20
rnA, or 50 rnA at least 1.8 volts at
100 rnA; at least 2 volts with AMPLI-
TUDE switch set to 200 rnA.
-----~--
I
Maximum Opposing Voltage and I
Current Mode (Steps and Opposing r
Offset)
XlO STEP button not illuminated
Refer to Type 576 Specification
X 10 STEP button illuminated
Polarity of step generator output cannot
be reversed using oppose offset.
-~-"---- -------------- --------
Step Rate I Power line
frequency; Type 576 .5X
RATE button pressed by projection on
I
176 rear panel.
-------
-------- ~----
-~-~-t-~-----------
Pulse Character-istics r
Width
I
300 fJ-S (80 fJ-S width also available but
performance not specified).
Duty Cycle (300 fJ-S pulsed steps)
Approximately 2':~
Step/Offset Polarity
r Same
as pulsed collector· supply polarity.
Reversible by pressing Type 576 STEP/
i
OFFSET POLARITY INVERT button.
------
____ ~_J __
--
--
Vertical and Horizontal Display Amplifiers
Display AccLir-acies
Horizontal
REV JUL 1981
------'1------------------
I Refer to Type 576 Specification
'-3

Specification-176
TABLE 1-1 (cont)
Characteristic
Performance Requirement
Supplementary Information
Vertical
2
Xl0 VERT button not illuminated
Refer to Type 576 Specification
Xl0 VERT button illuminated, 5
Within 3% of highest on-screen value
highest collector current settings
when vertical display is unmagnified.
only
When vertical display is magnified,
within 4% with 0 to 10 divisions off-
set, 3% with 15 to 35 divisions offset
and 2% with 40 to 100 divisions off-
set.
Deflection factors
Horizontal
Refer to Type 576 Specification
Vertical
Collector Current
Xl0 VERT button not Refer to Type 576 Specification
illuminated
Xl0 VERT button 1 A/division to 20 A/division in 1-2-5
illuminated,5 highest
sequence. Scale factor is indicated on
current settings only Type 576 PER VERT DIV readout.
2 Leakage (emitter current) measurements cannot be made when the 176 is being used.
Characteristic
Temperature
N on-operati ng
Operating
Altitude
Non-operating
Operating
Vibration (Non-operating)
Shock (Non-operating)
Transportation
1-4
TABLE 1-2
ENVIRONMENTAL CHARACTERISTICS
Performance Requirement
Supplementary Information
_40° C to +65° C
O°C to +40°C
To 50,000 feet
To 15,000 feet
15 minutes along each axis at 0.015 inch.
Vary frequency from 10 to 50 to 10 cis
in l-minute sweeps. Three minutes at any
resonant point or at 50 cis.
30 g's, 1/2 sine, 11
ms duration, 2 shocks
per axis
Qualified under National Safe Transit
Committee Test Procedure lA

176
SECTION 2
OPERA TING INSTRUCTIONS
INSTALLATION
To install the 176 in the Type 576, turn off the Type
576, remove the Standard Test Fixture and slide the 176
into place. Projections on the 176 rear panel press the STEP
FAMILY REP and .5 X RATE buttons on the Type 576
when the 176 is in place. To hold the 176 in place, tighten
the two fixture·securing screws on the front of the 176.
COOLING
The 176 has the same operating environment require·
ments as the Type 576. A fan is provided in the 176 which
draws cooling air in through the front of the fixture and
blows it out through louvered holes on the sides.
CONTROLS, INDICATOR LIGHTS
AND CONNECTORS
The functions of all the front panel controls, indicator
lights and connectors on the 176 (see Fig. 2·1) are
described in the
following table.
MAX PEAK POWER· Select peak power output of pulsed
WATTS Buttons collector supply. Each button lights
when pressed.
X10 VERT Button
When pressed, increases the deflec-
tion factor for the five highest cur-
rent positions of the Type 576
Warning Light
Fig. 2·1. 176 front-panel buttons, connectors and lights.
REV JAN 1982 2-1

Operating Instructions-176
Xl0 STEP Button
I nterlock Switch
WARNING Light
(Red)
VERTICAL switch by 10. The PER
VERT DIV readout indicates the
new deflection factor. The button
lights when pressed. The light goes
out and the deflection factor reo
turns to normal when the VERTI·
CAL switch is turned clockwise
beyond its five highest current posi·
tions.
When pressed, increases
the step
amplitude for the five highest cur·
rent positions of the Type 576
AMPLITUDE switch by 10. The
PE R STEP readout indicates new
step amplitudes.
The button lights
when pressed. The light goes out
and the step amplitudes return to
normal when the AMPLITUDE
switch is turned counterclockwise
beyond its five highest
current posi·
tions.
Enables the pulsed collector supply
when the Type 576 COLLECTOR
SUPPLY VOLTAGE DISABLED
light is on. It is pressed when the
protective box is in place and its lid
is closed.
When lit indicates that the pulsed
collector supply is enabled, and
dangerous voltage may appear at
the device testing jacks.
INTERLOCK OVER- Enables the pulsed collector supply
RIDE Button when the Type 576 COLLECTOR
SUPPLY VOLTAGE DISABLED
light is on. As a safety precaution,
the action of the button is momen-
tary.
WARNING I
When the protective box is not in place, pressing the
INTERLOCK OVERRIDE button makes operation
of the instrument potentially hazardous. Operators
should always be aware that dangerous voltages may
appear at the device testing jacks when the red
WARNING light is on.
Device Testing Jacks Allow connection of Tektronix
made 2, 3 or 5-terminal Test
Fixture Adapters to the 176. The
jacks also accept standard size ba·
nana plugs for remote testing. The
jacks labeled C, D and E are collec·
tor, base and em itter jacks, respec·
tively. The jacks labeled CSENSE
and ESENSE allow Kelvin sensing
of collector and em itter voltages.
2-2
BASE Jack
GROUN,D Jack
Ground Connector
Base steps appear at th is jack.
Provides external
access to ground
reference.
A
recessed sliding contact on left
side of the 176, which grounds the
176 to the Type 576 chassis to
prevent shock hazard.
GENERAL DESCRIPTION
The 176 High-Current Fixture extends the testing capa-
bilities of the Type 576 Curve Tracer. Using the pulsed
mode of operation, a device can be tested with pulsed
currents of up to 200 amperes. Since these current pulses
occur at a low duty cycle, a device can normally be tested
without the use of heat sinks. Also, the chance of damaging
the device is red uced.
Pulsed Collector Supply
The 176 pulsed collector supply produces current pulses
which are either 300 ps or 80 ps in duration. These pulses
are synchronized with the step generator output, and occur
at line frequency rate (60 Hz or 50 Hz). The voltage ampli-
tude of these pulses is determined by the Type 576 MAX
PEAK VOLTS switch and VAR IABLE COLLECTOR
SUPPLY control. Three of the MAX PEAK VOLTS switch
ranges (15, 75 and 350) are available for use with the 176.
The Type 576 MAX PEAK POWER WATTS switch is dis-
abled
when the 176 is being used. The MAX PEAK
POWER-WATTS buttons on the 176 provide power limiting
of the pulsed collector supply. Power may be limited to 10,
100 or 1,000 watts.
The Type 576 interlock system is also used in the 176.
When
the yellow Type 576 COLLECTOR SUPPLY VOL T-
AGE DISABLED light is on, the pulsed collector supply is
disabled. In th is case either the protective box or the
INTERLOCK OVERRIDE button can be used to enable
the pulsed collector supply. The protective box fits over the
device under test. When its lid is closed, the interlock
switch is pressed, which enables the pulsed collector supply.
Pressing the INTERLOCK OVERRIDE button also enables
the pulsed collector supply. The INTERLOCK OVERRIDE
button is used when the protective box cannot be used,
either because the device under test is too large or it is in a
remote
location. Whenever the pulsed collector supply is
enabled by the protective box or the INTERLOCK OVER-
RIDE button, the red 176 WARNING light goes on and the
yellow Type 576 COLLECTOR SUPPLY VOLTAGE DIS-
ABLED light goes out.
I WARNING I
When the protective box is not in place, pressing the
INTERLOCK OVERRIDE button makes operation
of the instrument potentially hazardous. Operators
should always be aware that when the red WARNING
light is on, dangerous voltages may appear at the
collector terminal of the device testing jacks.

Step Generator
When the 176 is being used, the Type 576 step generator
must be operated in the pulsed steps mode. Using this
mode, the step generator operates normally for all positions
of the Type 576 AMPLITUDE switch except for its five
highest
current positions. The step amplitude for each of
these five positions may be increased by 10 times by
pressing the 176 X10 STEP button. The increased step
amplitude is ind icated by the PE R STEP readout. With the
X10 STEP button pressed, the maximum step generator
output is 20 amperes. The X10 STEP button light will
remain
on until the AMPLITUDE switch is switched to a
position below the 10 mA position. When the X10 STEP
button light is out, the step generator operates normally.
NOTE
When the step generator is not in the highest
5 positions pushing the
X10 STEP button will not
change the step generator output but will change the
readout.
Either 300 j1S or 80 j1S pulsed steps may be selected. If
the Type 576 STEPS button is pressed, the 176 base step
amplifier and pulsed collector supply are disabled. No
damage resu Its to the device under test.
When the X 10 STEP button is ilium inated, both the
steps and the step offset, if any, are pulsed. Also, the range
of the Type 576 OFFSET MULT control is increased, 10
times giving it a total range of 100 times the setting of the
AMPLITUDE switch. When the X10 STEP button is not
illuminated, only the steps are pulsed. In this case, the
range of the OFFSET MULT control is 10 times the
AMPLITUDE switch setting.
The step generator rate is always line frequency when
the 176 is used, because a projection on the 176 rear panel
automatically presses the Type 576 .5X RATE button
when the 176 is installed. A similar projection presses the
STEP FAMILY REP button.
NOTE
An open base condition can be obtained by setting the
Type
576 step generator amplitude switch to .05 j1A.
Display Amplifiers
When the 176 is being used, the Type 576 display ampli-
fiers operate normally, except that the X10 VERT button
has been added to the 176 to add range to vertical measure-
ments, and leakage measurements cannot be made. When
the VERTICAL switch is set to one of its five highest
deflection factors and the 176 X10 VERT button is
pressed, the vertical deflection factor is increased 10 times
When
the button is pressed, it Iights and the increase in
Operating I nstructions-176
deflection factor is indicated by the PER VERT DIV read-
out. When the VERTICAL switch is turned clockwise
beyond its.1 A position, the X10 VERT button light goes
out and the VERTICAL switch returns to normal opera-
tion. The X10 VERT button does not affect the positioning
controls of the display amplifiers.
NOTE
When the VERTICAL DISPLA Y FACTOR is not in
the highest 5 display factors, the X10 VERT button
will not change the vert display but will change the
readout.
When the VERTICAL switch is set to STEP GEN and
the X10 VERT button is pressed, a 50 amperes/division
deflection factor is obtained. This deflection factor is not
indicated on the PER VERT DIV readout and its accuracy
is not specified.
Device Testing Jacks
Devices to be tested are connected to the 176 through
the five Device Testing Jacks. These jacks allow one device
to be tested at a time. Any of the Tektronix single-device
test fixtures adapters can be plugged into these jacks. These
adapters provide sockets into which devices with various
lead
arrangements may be placed for testing. Table 2-1 lists
the test fixture adapters available for use with the 176
when this manual was prepared. (Others may now be avail-
able.) These jacks also accept standard banana plugs so that
devices can be tested when it is inconvenient to use a partic-
ular device testing accessory, or when such an accessory is
not available.
TABLE 2-1
Test Fixture Adapters Which May Be Used With the 176
1
Tektronix Part
Number Case Type
013-0072-00
3 Diodes with axial leads (does
not provide
Kelvin sensing)
013-0100-00
3 TO-3
013-0101-00
3 TO-66
013-0110-00
2 Diodes with
stud leads; 00-4/00-5
013-0111-00
3 Diodes with axial leads (provides Kelvin
sensing)
013-0112-00
2 TO-36
1 This list contains only those test figure adapters available at the
time this manual was being prepared. Additional adapters may now
be available.
2Standard 176 accessory.
JStandard Type 576 accessory.
2-3

Operating I nstructions-176
The jacks labeled C, Band E are the collector, base and
emitter jacks, respectively. The jacks labeled CS
E
N SE and
ESENSE allow Kelvin sensing of voltages measured under
high
current conditions. Kelvin sensing means that current
is supplied to a device under test through one set of
contacts, and the voltage is measured through another set
of contacts. This method of sensing voltage eliminates
errors in voltage measurements due to contact resistance.
CSENSE and ESENSE stand for collector sensing and
em itter sensing, respectively.
EFFECTS OF 176 ON TYPE 576 CONTROLS
Since the 176 performs a specialized measurement
function, some of the Type 576 controls, connectors and
readout, do not perform the same functions as they wou Id
under normal operating conditions. The following table lists
the Type 576 controls and their functions when the 176 is
being used with the Type 576.
TABLE 2-2
Change
in Function of Type 576 Controls,
Connector and Readout When 176 is Used
Control
Change in Function
READOUTILLUM
None
GRATICULE I LLUM
None
INTENSITY
None
FOCUS None
VERTICAL
Leakage measurements can not be
made; 5 highest deflection factors
can be multiplied by 10 by pressing
176
X10 VERT button; STEP GEN
position provides 50
A/div deflec·
tion factor (with unspecified accu·
racy) when Xl0 VERT button is
pressed .
DISPLAY OFFSET None
Selector
CENTERLINE
None
VALUE
HORIZONTAL
None
POSITION (Vertical None
and Horizontal)
FINE POSITION None
(Vertical and
Horizontal)
2-4
ZERO
CAL
DISPLAY INVERT
MAX PEAK VOLTS
MAX PEAK POWER
WATTS
VARIABLE COLLEC-
TOR SUPPLY
POLARITY
MODE
LOOPING COM-
PENSATION
NUMBER OF STEPS
CURRENT LIMIT
AMPLITUDE
STEPS/OFFSET
OFFSET
OFFSET
MUL T
STEPS
300 fJ.S and 80 fJ.S
PULSED STEPS
STEP
FAMILY
RATE
POLARITY INVERT
.1X MUL T
COLLECTOR SUP-
PLY VOLTAGE
DISABLED Light
None
None
None
1500 position is d isab led.
Disabled
(MAX PEAK
POWER
WATTS
buttons on 176 used
instead).
None
AC position
is not usable
May be set to NORM or DC (ANTI-
LOOP).
LEAKAGE
(EMITTER
CURRENT) position is not usable.
Has no effect on display.
None
None
5 highest current step amplitues
can
be multiplied by 10 by pressing 176
X 10 STEP
button.
When 176
Xl0 STEP button is
lighted, offset is pulsed.
When 176
Xl0 STEP button is
lighted, the control becomes a 100
times multiplier.
Not usable.
None
REP ON button is automatically
pressed
by plastic projection on
176 rear panel.
.5X button is automatically pressed
by plastic projection on 176 rear
panel.
None
None
None
®

PER VERT DIV
10 times multiplication is indicated
Readout when
Xl0 VERT button is pressed.
PER HORIZ DIV
None
Readout
PER STEP Readout 10 times
multiplication is indicated
when 176
Xl0 STEP button is
pressed .
(3 OR gm PER DIV
None
Readout
CAME RA POWE R None
Connector
Line Voltage None
Selector Assembly
(Rear Panel)
50 Hz-60 Hz None
(Rear Panel)
FIRST TIME OPERATION
When the 176 is received, it is calibrated and should
perform within the specification shown in Section 1. The
following procedure allows the operator to become familiar
with the 176 controls and their relationship to the Type
576. This procedure may also be used as a general check of
the instrument's performance. For a check of the instru-
ment's operation with respect to the specification given in
Section 1, the performance check procedure in Section 5
must
be used.
1. Install the 176 in the Type 576. Press the Type 576
300 /1S PU LSED STEPS button.
2. Connect the Type 576 to a suitable power source and
turn on the Type 576.
3.
Allow the instruments to warm up for a few minutes.
The instrument should operate
within specified tolerances
five minutes after the
Type 576 has been turned on.
4. Set the 176 controls as follows:
MAX PEAK POWER·WATT 100
Xl0 VERT Not illuminated
XlO STEP Not illuminated
INTERLOCK OVERRIDE Not pressed
®
Operating Instructions-176
5. Set the Type 576 controls as follows:
READOUT I LLUM Visible Readout
GRATICULE I LLUM Visible Graticule Line
INTENSITY Visible Display
FOCUS Centered
VERTICAL
50mA
DISPLAY OFFSET
NORM (OFF)
Selector
CENTERLINE VALUE 0
HORIZONTAL 5 V COLLECTOR
Vertical Position Centered
Horizontal Position Centered
DISPLAY INVERT Released
MAX PEAK VOLTS 75
PEAK POWER WATTS Has no effect
VARIABLE COLLECTOR
Fully Counterclockwise
POLARITY
+ (NPN)
MODE
NORM
LOOPING COMPENSA-
Has no effect
TION
NUMBER OF STEPS 10
CURRENT LIMIT
20mA
AMPLITUDE 0.5/1A
OFFSET
ZERO
STEPS
Released
PULSED STEPS 300/1S
POLARITY INVERT
Released
STEP MULT .1X Released
6. Select an NPN power transistor with the following
characteristics:
(3
Ie max
BVCEO
Between 20 and 50
Greater than lOA
75 V
Install the transistor in a suitable Test Fixture Adapter
(TO-3, TO-36 or TO-66) and install the adapter in the
Device Testing Jacks
of the 176.
7. Put the protective box in place over the Test Fixture
Adapter and close the lid.
8. Press the Type 576 ZERO button and adjust the
spot to the intersection of the zero vertical and horizontal
graticule lines
of the CRT. Release the ZERO button.
9. Turn the Type 576 VARIABLE COLLECTOR
SUPPLY control clockwise to obtain a collector-emitter
voltage
of 50 volts (10 divisions horizontally).
10. Set the Type 576 AMPLITUDE switch to 10 mA
and adjust the VERTICAL switch for a display similar to
2-5

Operating I nstructions-176
that shown in Fig. 2-2. (The VERTICAL switch should be
set at one
of its five highest current positions.)
I l I
,If-J I I LJ
h ,I
r ~- t--
~ .
, +-
'.' ....... _tH~.· 't-++·t
H
... __ ." ..
• r - r----+---t--- + + t
! +-- -+- -+
'"
v
~ ,l).,
o.
'"
H
o
R
I
Z
o.
f'E" '.ll["
s
T
,
P
Fig. 2-2. Typical display of Ic vs V ce for 10 different steps of base
current for an NPN transistor.
11. Press the Type 576 OFFSET AID button and set
the OFFSET MUL T control for 2.00 (two steps of offset).
Note that the zero step (or pulse) of the display is no longer
on the zero horizontal graticule line. For normal pulsed
base operation of the Type 576 (with the X 10 STEP button
not illuminated) the offset voltage or current is not pulsed.
12.
Press the 176 Xl0 VERT button, which should
illuminate the button. Note that the size of the vertical
display
is decreased by 10 times due to the lOX increase in
the vertical deflection factor. The PE R VERT D IV readout
shou
Id also increase by 10 times.
13.
Press the X 10 STEP button, wh ich shou Id illu-
minate the button. Note that the size of the display in-
creases due to the 10 times increase in the step generator
step
amplitude. The PER STEP readout should also increase
by 10 times, Also note that the offset is now pulsed; thus,
the pulses start from the zero horizontal line rather than
from the offset level as discussed in step 11 for normal
operation.
14. Lift the lid of the protective box. Note that the
collector supply interlock opens and disables the collector
2-6
supply. This causes the red WARNING light on the 176 to
go out, the yellow COLLECTOR SUPPLY VOLTAGE
DISABLE light on the Type 576 to go on, and the display
to disappear.
15. Leaving
the lid of the protective box open, press the
176 INTERLOCK OVERRIDE button. This causes the
collector supply to be enabled. Note that when the button
is pushed, the yellow COLLECTOR SUPPLY VOLTAGE
DISABLE light goes out, the red WARNING light goes on
and ad isplay re-appears.
I WARNING I
Pressing the INTERLOCK OVERRIDE button when
the protective
box is not in place enables the collector
supply and makes operation of the instrument
potentially dangerous. Operators should always be
aware that when the red WARNING light is on,
dangerous voltage may appear at the collector ter-
minal.
16. Release the INTERLOCK OVERRIDE button and
close
the lid of the protective box.
17. Press the 1000 MAX PEAK POWER-WATTS
button. Note that the maximum peak power being dis-
sipated by the device under test (Ic versus V
CE
) increases.
18.
Press the 176 10 MAX PEAK POWER-WATTS
button. Note that the maximum peak power decreases.
Press the 100 MAX PEAK POWER-WATTS button.
19. Set the Type 576 AMPLITUDE switch to 5 mAo
Note that the 176 X 10 STEP button light goes out, and the
step generator step amplitude is no longer multiplied by 10
times.
20. Set the Type 576 VERTICAL switch to 50 mAo
Note that the 176 X 10 VERT button light goes out, and
the vertical deflection factor is no longer multiplied by 10
times,
This completes the first time operation procedure.

WARNING
THE FOLLOWING SERVICING INSTRUCTIONS
ARE FOR USE BY QUALIFIED PERSONNEL
ONLY. TO AVOID PERSONAL INJURY,
DO NOT
PERFORM ANY SERVICING OTHER THAN THAT
CONTAINED IN OPERATING INSTRUCTIONS
UNLESS YOU ARE QUALIFIED TO
DO SO.
REFER TO OPERATORS SAFETY SUMMARY
AND SERVICE SAFETY SUMMARY PRIOR TO
PERFORMING ANY SERVICE.

176
SECTION 3
MAINTENANCE
INDEX OF MAINTENANCE INFORMATION
The following table is a general index of the information
found in section 3 through 8.
Adjustment
Procedure
(page 5·5)
Block Diagram
Description
(page 4-1)
Circuit Board
Pictures
(section 7)
Circuit Description
(page 4·1)
Corrective
Maintenance
(page 3-3)
REV JAN 1982
The adjustment procedure describes
the single internal adjustment in the
176.
The
block diagram description
provides a functional description of
the electrical operation of the 176.
A
functional block diagram is
shown in Fig. 4-1 and an inter-
connection block diagram is
provided at the beginning of the
diagrams section.
Circuit board pictures accompany
most diagrams in section 7. Each
picture shows the locations of the
circuit board-mounted components
in the diagram. The pictures are
located either on the apron of the
fold·out diagram or on the back of
the preceding diagram. The loca-
tions of Chassis-mounted compo-
nents are not shown. Each circuit
board is identified by an assemb Iy
number. I nformation regard ing
assembly numbers is discussed at
the beginning
of the diagrams
section.
The circu it description provides a
detailed description of the electrical
operation of the circuits of the 176.
Simplified schematics are included.
The corrective maintenance section
provides
information for: ordering
electrical and mechanical compo-
nents; tuning and replacing the coils
of the charge lines; replacing
semiconductors; removing and
Diagrams
(section 7)
Electrical Parts List
(section 6)
Mechanical Parts
List and Mechanical
Illustrations
(section 8)
Performance Check
(page 5-1)
replacing relays; replacing push
button bulbs; and soldering on
circuit boards.
A
complete set of circu it diagrams
is given in the fold-out pages in
section
9. Also included in the
diagrams section are an
intercon-
nection block diagram, circuit
board pictures, and voltages and
waveforms. I
nformation regard ing
diagram symbols, voltage and wave-
form cond itions, and assembIy
numbers can be found at the
beginning
of the diagram section.
The electrical parts list is organized
first by assembly number (with a
separate list
of chassis mounted
components) and then by circuit
number. Circuit number abbrevia-
tions and assembly numbers are
discussed at the beginning
of the
diagrams section. Other abbrevia-
tions used in the electrical parts list
along
with electrical parts ordering
information can be found at the
beginning
of the parts list.
The mechanical parts list is ar-
ranged by mechanical parts illustra-
tion number and by the item
numbers in each
illustration. The
mechanical illustrations are located
on the backs of the last three
diagrams in section 7.
The performance check procedure
allows the operation of the 176 to
be checked against the electrical
characteristrics given under perfor-
mance requirements in section 1. It
may be used both for incoming
inspection and to provide periodic
checks of the instrument operation.
3-1

Maintenance-176
Preventive
Maintenance
(page 3-1)
Troubleshooting
(page 3-2)
Waveforms and
Voltages
(section 7)
The preventive maintenance section
provides
information on cleaning,
visual inspection and readjustment
of the 176.
The troubleshooting section lists
equipment which will be helpful in
troubleshooting the 176 as well as a
general procedure for trouble-
shooting the 176.
Typical voltage measurements and
waveform photographs are given on
the diagrams in the diagrams
section.
The voltages are written on
the circuit diagrams and the wave-
form pictures are normally found
on the apron of each diagram.
Voltages and waveforms conditions
are given at the beginning of the
diagrams section.
PREVENTIVE MAINTENANCE
General
Preventive maintenance consists of cleaning, visual
inspection, etc. Preventive maintenance performed on a
regular basis will improve the reliability of this instrument.
The severity of the environment to which the 176 is sub-
jected determines
the frequency of the maintenance.
Cleaning
The best method of cleaning the exterior of the 176 is
with a cloth dampened in a mild detergent and water solu-
tion. Abrasive cleaners should not be used. A small paint
brush may also be useful for dislodging dirt on and around
the
front panel controls. The best method of cleaning the
interior of the 176 is to blowout the accumulated dust
with dry, low velocity air. Remove any dirt which remains
with a soft paint brush or a cloth dampened with a mild
soap and water solution. A cotton-tipped applicator is also
useful
for cleaning the narrow spaces on circuit boards.
Avoid the use of chemical cleaning agents which
might damage the plastic used in this instrument.
Avoid chemicals which contain benzene, toluene,
zylene, acetone or similar solvents.
The air filter should be visually checked every few weeks
and cleaned
or replaced if dirty. More frequent inspections
are required under severe operating
conditions. If the filter
3-2
is to be replaced, order new air filters from your local
Tektronix Field Office or representative. The following pro-
cedure is suggested for cleaning the filter:
1. Remove one of the plastic side panels from the 176
and slide out the blue front panel. The filter may now be
pulled out of the retaining frame in front of the fan.
2. Flush
the loose dirt from the filter with a stream of
hot water.
3. Wash the filter in soap and hot water.
4. Rinse the filter in clear water and allow it to dry.
5. Re-install the filter in the retaining frame, then re-
place the front panel and the side cover.
Visual Inspection
A brief visual inspection of the 176 should precede any
performance check or readjustment. In making a visual
inspection, look for broken connectors, loose pin connec-
tors, heat damaged parts and damaged circuit boards.
Performance Check and Readjustment
To insure accurate operation, the performance of the
176 should be checked after each 1000 hours of operation
or each six months, and, if necessary, readjusted. In addi-
tion, replacement of components may necessitate readjust-
ment of the instrument. Complete performance check and
adjustment instructions are provided in section 5.
TROUBLESHOOTING
Troubleshooting Equipment
1. Transistor Tester-some means of testing the semi-
conductors used in the instrument is helpful. A transistor
curve tracer such as the Tektronix Type 576 or Type 575
will give the most complete information.
2. DC Voltmeter and Ohmmeter-A 20,000 ohm/volt
VOM can be used to check voltages and resistances. When
checking voltages allowance
must be made for circuit
loading at high impedance points.
3. Test oscilloscope-A test oscilloscope is required to
view waveforms at different points in the circuit. An
oscilloscope with DC to 20 MHz frequency response and
®