HP 141S Service manual

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OPERATING AND SERVICE MANUAL
\
.\
DISPLAY
SECTION
141S
.. .
HEWLETT i:IJ PACKARD

DIGITALY REMASTERED
OUT OF PRINT
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02639-1
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tJ--------.
OPERATING AND SERVICE MANUAL
MODEL 1415
DISPLAY SECTION
SERIALS PREFIXED: 825-
For Instruments With Other Serial Prefixes, See Section 1.
Copyright HEWLETT -PACKARD COMPANY;COlORADO SPRINGS DiVISION 196 B
1900 GARDEN OF THE GODS ROAD. COLORADO SPRINGS. COLORADO. U S. A
PRINTED: OCT 1968
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Table of Contents
Model 141S
TABLE OF CONTENTS
Section
Page Section Page
GENERAL INFORMATION 1-1
4-47. Compensation Attenuator 4-5
1-I. De sc ri ption 1-1
4-5l.
Plug-In Kit Fabrication·
4-5
1-6.
Cathode-Ray Tube
1-1
1-8. CRT Warranty 1-1
V MAINTENANCE
5-1
1-10. Associated Equipment 1-1 5-I. Introduction . 5-1
1-13. Manual Identification 1-2 5-3. Performance Check 5-1
1-15. Scope of Manual· 1-2 5-4. CRT Controls 5-1
5-7. Calibrator 5-1
II INSTALLATION· 2-1 5-8. Adjustments 5-2
2-I.
Inititial Inspection
2-1 5-13. Adjustments of Low-Voltage
2-4.
Preparation for use·
2-1
Supply 5-2
2-5. Power Requirements 2-1 5-15. Adjustments of High- Voltage
2-9. Instrument Mounting 2-1 Supply 5-2
2-12.
Instrument Cooling 2-1 5-16. Intensity Limit Adjustment 5-2
2-15. Claims
2-1
5-17. Astigmatism Asjustment 5-2
2-17. Repackaging for shipment 2-2 5-18. Geometry Adjustment. 5-2
5-19. Calibrator Adjustment 5-5
III OPERATION 3-1 5-20. Pulse Circuit Adjustment 5-5
3-I.
Introduction·
3-1 5-22. Compensation Attenuator
3-3.
Front Panel Components 3-1
Adjustments 5-6
3-10. Rear Panel Components
3-1
5-24.
Troubleshooting 5-7
3-14. Plug-In Units 3-1 5-25. Low- Voltage Supply 5-7
3-18. Operating Considerations 3-1
5-32. High- Voltage Supply· 5-7
3-19. Definitions
3-3
5-37.
Pulse Circuit 5-7
3-2l. Control Functions
3-3
5-41.
Periodic Maintenance· 5-8
3-25. Operating Tips 3-3 5-42. Electrical Maintenance
5-8
3-27. Single- shot Operation
3-5
5-44.
Mechanical Maintenance 5-8
5-46. Instrument Repair 5-8
5-49. Major Component Repair 5-8
IV PRINCIPLES OF OPERATION 4-1 5-53.
Servicing Circuit Boards· 5-9
4-l. Functional Description 4-1
4-8. Circuit Description' 4-1
VI REPLACEABLE PARTS 6-1
4-9. Low- Voltage Power Supply 4-1 6-1. Introduction'
6-1
4-17. Calibrator 4-2 6-4. Ordering Information' 6-1
4-2l. High- Voltage Power Supply 4-3
4-27.
Storage CRT .
4-3 APPENDIX I IA-1
4-34.
Pulse Circuit
4-4 MANUAL CHANGES AND OPTIONS IA-1
4-32. Clamp Circuit 4-5
lA-I. Options IA-1
4-45. Trace Align 4-5
IA-6. Manual Changes IA-l
ii
02639-1
•
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Model 141S List of Illustrations
List of Tables
LIST OF ILLUSTRATIONS
Figure Title
1-1. Model 141S Oscilloscope
2-1. Rack Mounting Procedure·
3-1. Model 141S Controls·
3-2. Proper Intensity Adjustments·
3-3. Background Illumination
3-4. Variable Persistence
3-5. Single-Shot, Trace Bloom
3-6. Single-Shot, No Bloom
3-7. Fade Positive
3-8. Single-Shot, Fast Sweep·
3-9. Single-Shot, Fade Positive
3-10. Storage Mesh Imperfections
4-1.
4-2.
4-3.
4-4.
4-5.
5-1.
5-2.
5-3.
5-4.
Model 141S Block Diagram
Regulated Power Supply Block Diagram
High- Voltage Power Supply Block
Diagram
Pulse Circuit Block Diagram .
Erase: Functional Waveform·
Pincushioning and Barrelling .
Adjustment and Component Locations,
Bottom View
Component Locations, Top View
High- Voltage Deck Removal
Page
· 1-1
·2-2
·3-2
·3-4
· 3-5
· 3-5
· 3-5
· 3-5
· 3-6
· 3-6
· 3-6
· 3-6
· 4-1
·4-2
·4-3
·4-4
· 4-5
· 5-2
· 5-3
· 5-4
· 5-9
Figure
5-5.
5-6.
5-7.
5-8.
5-9.
5-10.
5-11.
5-14.
5-13.
5-14.
5-15.
5-16.
5-17.
6-1.
lA-I.
LIST OF TABLES
Figure Title Page Figure
1-1. Specifications
· 1-0
5-4.
2-1. Shipping Carton Test Strengths·
·2-2
5-5.
4-1. Current Capability
· 4-5
5-6.
6-1.
5-1. Equipment Required for Tests and
Adjustments
· 5-0
6-2.
5-2.
Low-Voltage Adjustments
· 5-2
5-3. Condensed Adjustment Procedure
· 5-5
lA-I.
02639-1
Title
CRT Appearance, Pulse Circuit
Adjustments
Oscilloscope Plug-in Jack Connections·
Spectrum Analyzer Plug-in Jack
Connections
Component Identification, Low-Voltage
Board, A401
Low-Voltage Schematic Diagram
Component Identification, Horizontal
Driver Board, A603
Component Identification, Compensation
Attenuator Board, A605
Component Identification, High-Voltage
Rectifier Board A601
Component Identification, High-Voltage
Regulator Board, A602
High- Voltage Schematic Diagram·
Waveforms
Component Identification, Pulse Board
A701, and Clamp Board, A704·
Pulse and Clamp Circuit Schematic
Diagram
Cabinet Parts, Exploded View
Remote ERASE Circuit
Title
Troubleshooting High-Voltage Supply,
No Voltage
Troubleshooting High-Voltage Supply,
Incorrect Voltage·
Schematic Diagram Notes·
Reference Designators and Abbrevia-
tions
Replaceable Parts·
Replaceable Parts Added for Option 09 .
Page
5-11
5-12
5-12
5-13
5-13
5-14
5-14
5-14
5-15
5-15
5-16
5-17
5-17
·6-2
IA-1
Page
· 5-8
· 5-8
5-10
· 6-1
·6-3
IA-1
iii
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Section I
Table 1-1
Table 1-1
PLUG-INS:
Accepts Model 8552AIF Section and Model 8553L
RF Section Spectrum Analyzers without the use
of a center divider shield.
Also accepts all Model 1400-Seriesplug-ins. All
plug-ins operate into horizontal and vertical com-
pensation attenuators. Center shield may be re-
moved to provide double-sized compartment for
use with a single dual axis Model 1400- series unit.
CATHODE-RAY TUBE:
~
Type:
Post-accelerator storage tube; 7350 V accel-
erating potential; aluminized P31 phosphor;
etched safety glass face plate reduces glare;
transparent coating to reduce RFI.
Graticule:
8 x 10 divisions (approximately 6, 6 x 8, 2 cm);
five subdivisions per major division on hori-
zontal and vertical axes.
Intensity Modulation:
(Used only with 1400-series plug-ins. )
AC coupled, +20 V
pulse will blank trace of
normal intensity; input terminals on rear panel.
Warranty:
CRT specifications (perSistence, writing rate,
brightness, storage time) warranted for one
year.
PERSISTENCE:
Normal:
Natural perSistence of P31 phosphor (about
40 J-L sec to 1cf!6 of original brightness.
Variable:
NORMAL Writing Rate Mode: Continuously
variable from less than O. 2 second to more
than one minute (typically to two or three
minutes).
MAX Writing Rate Mode: Typically variable
from O. 2 second to 15 seconds.
ERASE:
Manual; erasure takes approximately 100 msec;
scope ready to record immediately after
erasure (see options for remote erase).
WRITING RATE:
1-0
Conventional operation (using an hp 197A camera
with f/l. 9 lens and Polaroid 3000 speedfilm):
100 cm/J-Lsec.
Storage:
NORMAL Mode: greater than 20 cm/ms.
MAX Mode: greater than 1 cm/J-Lsec.
Model14lS
Spec ifications
STORAGE TIME:
~------------~----------~
NORMAL Writing
Rate Mode
STORE Mode
longer than 1 hour
(dim display)
VIEW Mode longer than 1
(bright display) minute (typically
2 or 3 minutes)
Brightness:
MAX Writing
Rate Mode
typically 15
minutes
typically 15
seconds
Greater than 100 foot-Iamberts in NORMAL
or VIEW; typically 5 foot-Iamberts in STORE.
CALIBRATOR:
(Used only with 1400-series plug-ins. )
Type:
Line-frequency rectangular signal, approx-
imately O. 5 J-L sec rise time.
Voltage:
Two
outputs: 1 volt and 10 volts pk-pk ± 1% from
15° C to 35° C, ±3% from 0° C to 55° C.
BEAM FIN DER:
PreSSing BEAM FINDER control brings defocused
trace on screen regardless of setting of horizontal
or vertical controls.
GENERAL:
Power Requirements:
115 or 230 volts, ±10%, 50-60Hz, normally
less than 285 watts (varies with plug-in units
used).
Dimensions:
NOTE
DIMENSIONS IN INCHES AND (MILLIMETERS)
® ~6~ ~:~fN~~I~~rd~N.f1PNO~~3oj~~L~:EVtfTJD
Ii (8) TO EtA RACK HEIGHT
®REAR APRON RECESS
Weight:
h- --16~(425)-------..,,.;' __ -.
il. ::::IrT 1
i, ,Jl,
TOP 16
®t mmm mnnm <or l
T
~ .f------.--- 19 (483) --------.' ~
I ... I ~
Net, 40 lbs. (18 kg) (without plug-ins).
Shipping, 51 lbs. (23 kg).
OPTIONS: (Specify by option number.)
09: Remote erase. BNC input on rear panel;
shorting to ground for at least 50 msec erases
screen; input draws 20 rna from ground through
a 600-ohm impedance to a -12 volt supply.
02639-1
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Model 141S
Section I
Paragraphs 1-1 to 1-11
SECTION I
GENERAL
INFORMATION
1-1. DESCRIPTION.
1-2. The Model 141S, Figure 1-1, is the Display Sec-
tion of the HP Model 141S /8552A/ 8553L Sp ec trum
Analyzer. Model 141S has the added features of vari-
able persistence (duration of trace afterglow) and
storage of CRT displays. Persistence is variabl e
from 0.2 to more than 60 seconds; a display may be
stored (at reduced .ensity) for more than 1 hour or
displayed at normal intensity for up to 1 minute.
Stored displays can be erased in 100 milliseconds.
1-3. Variable persistence is especially useful for
viewing slow-sweep signals. The persistence of the
signals from electrocardiograms or other bio-chem-
ical phenomena can be adjusted to provide a complete
trace, yet to fade fast enough to prev ent interference
with the next trace. Display persistence of swept
frequency and time-domain reflectometry measure-
ment readouts can be adj usted to eliminate flicke rand
still provide high reso luti on.
1-4.
The storage feature of the Model 141S can be
used to store single-shot waveforms and later to view
or photograph the phenomena. Comparison of Wave-
forms can be accomplished by storing several displays
separately and then viewing them simultaneously.
1-5. The Model 141S accepts Model 8552A IF S ect ion
and 8553L RF Section Spe ctrum Analyzer plug-ins and
all HP Model 1400- series plug-in units. Amplifiers with
bandwidths up to 20 MHz and sensitivities to 10 micro-
volts per centimeter are ava il able as well as time-
domain reflectometry and swept frequency indicator
units. Complete specifications for the Model 141S
Display Section are given in Table 1-1.
1-6. CATHODE-RAY TUBE.
1-7. The Model 141S uses an internal graticule, P31
aluminized phosphor CRT with a transparent coating
to reduce RFI. Additional internal e lem en ts provide
variable persistence and storage features. The tube
is equipped with a nonglare safety face plate and the
inte rnal graticule eliminates parallax error in observ -
ing the display.
1-8. CRT WARRANTY.
1-9. The CRT used in the Model 141S is covere d by
a
warranty separate from the instrument warranty.
The CRT warranty is included in the back of this man-
ual for use in the e vent of CRT failure during the
warranty p eriod listed ther eon.
1-10. ASSOCIATED EQUIPMENT.
1-11. The Model 141S , Display Section is designed
specifically for use with Model 8552A/ 8 553L Spectrum
Ana lyzer Plu g -in units . The Oper ation and service
Manual for these units give complete information on
installation and operation on the units.
Figure 1-1. Model 141S Oscilloscope
02639-1 1-1
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Section I
Paragraplls 1-12 to 1-18.
1-12. Model141S
also accepts all HP 1400- series time-
domain plug-ins listedin the Hewlett-Packard Instru-
mentation Catalog. Tile Model 141S is normally oper-
ated with a vertical plug-in in be upper compartment.
Both plug-in compartments are the same size and the
plug-in instruments may be intercimnged for any
special application. The divider shield, which separ-
ates the two compartments, may be removed and one
double sized plug-in installed. Blank plug-in kits,
both single and double sized, are available for user
fabrication of special circuits. See Table 4-1 for power
supply current lilm tations.
1-13. MANUAL IDENTIFICATION.
.,
1-14. Information in this manual applies di rectly to
Model 141S instrumentswiti1 serial prefix of 825-. The
serial prefix is the first 3 digits of Cl€ eigilt-digit
serial n u m be r (000-00000) used to ide n t i fy each
Hewlett-Packard instrument. If the serial prefix of
a Model 141S is not 825-, a change s;,eet supplied with
Lie manual w;ll define the differences between Llat
Model 141S and tne one described in this man u a 1.
Corrections to t;lis manual due to any errors which
existed at the time of printing are call e dEl' rata
1-2
Model 141S
and appear Jnly on L1e c"ange sheet supplied. Fo r
information pertaining to change sheets, contact the
nearest Hewlett-Packard Sales IService Office.
1-15. SCOPE OF MANUAL.
1-16. The intent of this manual is to provide the user
of the Model 141S with all necessary information to
apply this instrument to the full extent of its capabil-
ities. Because the Model 141S Display Section may be
used not only as a Spectrum Analyzer but also as a
conventional oscilloscope, the manual contains infor-
mation pertinent to both usages.
1-17. Primarily, the Model141S is intended for use as
the Display Section of the 141S/8552A/8553L Spectrum
Analyzer. Therefore all discussions in succeeding
sections of this manual will deal first with this appli-
cation. Immediately following will be information
applicable to conventional oscilloscope operation with
HP Model1400-series time-domain plug-ins.
1-18. In view of this treatment of subject material, the
user should bear in mind that there may be variations
in adjustments, checks and procedures depending on
the use being made of this instrument.
02639-1
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Model 141S
Section II
Pal'C1grapls 2-1 to 2-16
SECTION II
INSTALLATION
2-1. INITIAL INSPECTION.
2-2. MECHANICAL CHECK. If external damage to
the shipping carton is evident, ask the carrier's
.:gent to be present when tne instrument is unpacked.
Check the instrument for external damage such as
broken controls or connectors, and dents or scratches
on the panel surfaces. If damage is found, see Para-
graph 2-15 for recommended claim procedure. If the
shipping carton is not damaged, check the cushioning
material and note any signs of severe stress as an
indication of rough handling in transit. If the instrument
appears undamaged, perform the electrical check
(Paragraph 2-3). Retain the packaging material for
possible future use.
2-3. ELECTRICAL CHECK. Check the electrical
performance of the Model 141S a s soon a s possible
afte r receipt. Paragraphs 5- 3 through 5- 5 contain
per form a n c e check procedures which will verify
instrument operation within the specifications listed
in Table 1-1. Initial pe rformance and accuracy of the
instrument are certified as stated on the inside front
cover of this manual. If the ins t I' U men t does not
op e I' ate as specified, refer to Paragraph 2-15 for
recommended claim procedure.
2-4. PREPARATION FOR USE.
2-5. POWER REQUIREMENTS.
Before placing this instrument in ope ration,
be sure and set rear panel switch to agree
with the line voltage being used. Refer to
Figure 3-2, Proper Intensity Adjustment,
to avoid damaging CRT.
2-6. The Model 1418 Display8ection requires apower
source 0 f either 115 0 I' 230 volts ac, +10%, single
phase, 50-60Hz, which can deliver approximately
300 watts. A rear panel switch provides appropriate
transformer connections for the line voltage to be used.
2-7. 230-VOLT OPERATION. If the instrument is
to be operated from a 230-volt source, set the rear
panel switch to 230. The line fuse, F401, must be
changedtoa 2-amp slow-blow fuse for 230-volt oper-
ation. The fuse is accessible by removing the bottom
cover of the Model 141S. It is identified in Figure 5-1.
2-8. THREE-CONDUCTOR POWER CABLE. National
Electrical Manufacturers Association (NEMA) recom-
mends that instrument panel and cabinet be grounded
for the protection of operating personnel. The Model
141S is equipped with a detachable, three-conductor
power cable which, when plugged into an appropriate
receptacle, grounds the instrument. The offset (round)
pin on the power cable connector is the ground pin.
To preserve the protection feature w hen operating
02639-1
the Model 141S from a two-contact outlet, use a three-
conductor to two-conductor adapter and connect the
g I' e e n lead on the adapter to ground at the power
outlet.
2-9. INSTRUMENT MOUNTING.
2-10. MODULAR CABINET. The Model 1418 is
shipped from the factory as a bench instrument with
the tilt stand, feet, and plastic trim inplact'. The top
and bottom panel covers can be removed, [',ivingcom-
plete accessibility to all componl'nts and adjustments.
Sufficient space should be left arounci the sides uf the
cabinet to allow unres tricted air c ircuLltion.
2-11. RACK MOUNTING. A kit for converting the
modular cabinet to a rack mount is supplied with each
Model 1418. Instructions for making the cunversion
arc [',iven below. Refer to Figure 2-1 as an aid to
identifvin[',
parts.
a. Detach tilt stand by pressing away from front
feet: remove all plastic feet by depressing metal but-
ton and sliding foot frt'e.
b. Aluminum trim strips (behind each front handle)
on sides ur instrument have an adhesive back; use a
thin-blade tool tu remove them.
c. Attach a rack-mounting fhmge. using screws
provided in kit, in each space where trim strip was
adhered; larger notch of flange should be positioned
at instrument bottom.
d. If Model 1418 is to be placed in a rack above or
below another hp instrument, attach filler strip pro-
vided with kit between front panels of instruments.
2-12. INSTRUMENT COOLING.
2 -13. The Model 1415 uses a forced-air cooling system
to maintain reasonable operating temperatures within
the instrument. Warm air is exhausted through the
side panel perforations. When operating the instru-
ment, choose a location which provides at least three
inches of clearance around the rear and both sides.
2-14. The cooling fan and air filter require periodic
lubrication and c leaning. Refer to Paragraph 5 -41
for maintenance instructions.
2-15. CLAIMS.
2-16. The warrantv statement applicable to all Hewlett-
Fackard Company instruments andproducts is provided
inside the front cover of this manual. If phys ical
damage is found or if ope ration is not as specified when
the instrument is first received, notify the carrier
and the nearest Hewlett-Packard Sales IService Office
immediate ly. The Sales 'Service Office will arrange
for repair or replacement of the instrument without
waiting for settlement of a claim with the carrier.
For other than initial inspection warranty claims,
contact the Sales 'Service Offic e.
2-1
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Section II
Paragraphs 2-17 to 2-19.
2-17. REPACKAGING FOR SHIPMENT.
2-18. If the Model 141S is to be shipped to a Hewlett-
Packard Sales/Service Office for service or repair,
attach a tag showing owner (with address), instrument
model nuinber, full serial number of the instrument
(all 8 digits) and description of the service or repair
required.
2-19~he original shipping carton and packaging ma-
terial, with the exception of accordion-pleated pads,
may be reused, if undamaged. The Sales/Service
Office will provide information and recommendations
on materials to be used if the original packaging
material is not available. Materials used for shipping
an instrument should include the following:
a. A double-walled carton, see Table 2-1 for test
strength required.
TILT STAND
FILLER STRIP .
(
/
;>< 0
....---::~~ •.o
; ~ /
/' :"/;
TRIM STRIP ~ ~ -r: RACK MOUNTING
(ADHESIVE BACK)
~ FLANGE
Model14lS
Table 2-1. Shipping Carton Test Strengths
Gross Weight (lbs) Carton Strength (test Ibs)
up
to 10 200
10
to 30 275
30
to 120 350
120
to 140 500
140
to 160 600
b.
Heavy paper or sheets of cardboard to protect
all instrument surfaces; use a nonabrasive material
such as polyurethane or cushioned paper suchas Kim-
pak around all projecting parts.
c. At least 4 inches of tightly-packed, industryap-
proved, shock-absorbing material such as extra firm
polyurethane foam.
d. Heavy-duty shipping tape for securing outside
of carton.
/"1
I
FOOT RELEASE
BUTTON
i ~PLASTIC
, FOOT
v)
I ;
'/
~; 0
I !J~
7000- 6-18
Figure 2-1. Rack Mounting Procedure
2-2 02639-1
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Model14lS
Section In
Paragraphs 3-1 to 3-17
SECTION III
OPERATION
3-1. INTRODUCTION.
3-2. The Model14lS Display Section employs a vari-
able persistence, storage type CRT and accepts Spec-
trum Analyzer or 1400 Series time-domain plug-ins.
Controls which affect operation of the power supplies
and cathode-ray tube are located on the Model l4lS,
all other controls are located on the plug-in units.
The Model14lS includes the high and low voltage power
supplies, a calibrator circuit with 1 and 10 volt pk-pk
outputs, a compensation attenuator circuit, a pulse
circuit for variable persistence and storage operation,
and the CRT.
3-3. FRONT PANEL COMPONENTS.
3-4. Figure3-1 identifies the fro ntpanel controls and
gives a brief functional description of each. Additional
information on some of the controls is given below.
A more detailed description of some of the controls
and their function in variable persistence and storage
operation is given in Paragraph 3-17.
3-5. TRACE ALIGN. The TRACE ALIGN adjust-
men t is provided to compensate for manufacturing
tolerances and external magnetic fields which may af-
fect the CRT trace. The adjustment should be made
when the trace does not appear parallel with the hori-
zontal lines on the CRT graticule. To adjust the
TRACE ALIGN, set the Presentation Selector to WRITE
and adjust a free- running trace on the CRT; rotate the
TRACE ALIGN adjustment a s required to make the
trace parallel to the graticule lines.
BEAM TINDER should be depressed only
momentarily and then released. If it is
held depressed, damage to the CRT may
occur.
3-6. BEAM TINDER. A very high dc input signal
may drive the trace off the CRT screen. When the
BEAM TINDER is depressed, the trace is returned
to the screen. Adjust the POSITION control to center
the beam and when the BEAM FINDER is released,
the trace should remain on screen. Hthe front panel
INTENSITY control is fully counter-clockwise, the
trace may not be visible. If the trace is not visible
when the BEAM FINDERis depressed, set INTENSITY
to 10 o'clock pOSition.
3-7. ASTIGMATISM. The ASTIGMATISM adjustment
is provided to insure uniform focus of the trace over
the entire CRT screen. Toadjustthe ASTIGMATISM,
set Presentation Selector to WRITE, center a low-
intensity spot on the CRT screen (WRITING RATE and
PERSISTENCE both in NORMAL) and adjust FOCUS
and ASTIGMATISM for a small, round, sharply focused
spot.
02639-1
3-8. CALIBRATOR. To avoid damage to the Model
8553L RF Sec t ion do not connect the output of the
Calibrator to the Spectrum Analyzer Plug-ins. Refer
to the Operating ~uld Service Manual of the 8552A "8553L
for proper Calibration procedures when using Spectrum
Analyzer plug-ins.
3-9. Paragraph 5-19 contains CALIBRATOR adjust-
ment procedures when 1400 series plug-ins are em-
ployed.
3-10. REAR PANEL COMPONENTS.
3-11. 115/230 VOLT SWITCH. This switch, located
at the bottom of the rear panel, must be set to the
position which corresponds to the line voltage to be
used. The Model 141S is shipped with a 4-amp fuse
installed for 115-volt operation. If the Model 141S
is to be connected to a 230-volt outlet, change the fuse
to a 2-amp, slow-blow fuse supplied with the instrument.
3-12. Z-AXIS INP'JT. When the Model 141S is used
with Spectrum Analyzer plug-ins, the Z Axis terminals
and selector switch on the rear panel are inoperative.
3-13. To modulate the trace intensity externally
in conventional oscilloscope applications, set tile
switch to EXT, remove the shorting strap and cOlmect
the modulation signal to the terminals. The amplitude
of the pulse required to blank the trace depends on
the front panel INTENSITY control setting, and is
approximately 20 volts positive for normal intensity
settings. When not using external intensity modulation,
connect the strap across the terminals and place the
switch to INT.
3-14. PLUG-IN UNITS.
3-15. For operation as a Spectrum Analyzer, install
Model 8552A IF Section and Model 8553L RF Section
in plug-in compartment as outlined in Operating and
Service Manual for these units.
3-16. When setting up for conventional oscilloscope
operation, insert desired plug-in units in the upper
and lower compartments. The compartment divider
plate must be in place to provide proper shielding
between the plug-ins. For double-size plug-in opera-
tion, rem 0 v e the divider. All plug-ins should be
sec u rei y 10 c ked i n p I ace with the front panel
LOCK knob.
3-17.
Deflection-plate sensitivity may vary slightly
from one CRT to another. This may necessitate ad-
justment of the sensitivity calibration of plug-ins in-
stalled in the Model 141S for the first time, or when
moved from one Model 141S to another. Refe l' to the
Operating and Service Manual furnished with plug-in
unit for the SENS ICAL adjustment procedure.
3-1
Scans by Artekmedia => 2010

Section TIl
Figure 3-1
2
3
4
10
6 7 8 9 5
1. Adjustment to set trace parallel with horizontal
graticule lines.
2. Momentary switch to return beam to CRT regard-
less of vertical and horizontal POSITION control
settings. See CAUTION statement in Paragraph
3-6.
3. ON pOSition connects AC power to Oscilloscope
and lights POWER indicator.
4. Control for focusing beam on CRT .
5. Adjustment to set roundness of CRT beam.
Model141S
1415 -A-I
6. Control for setting intensity (brightness) of CRT
display. See CAUTION statement in Paragraph
3-18.
7. Controlfor setting trace perSistence (afterglow)
on CRT.
8. Presentation Selector, for selecting function of
CRT.
9. Switch for selecting CRT writing rate.
,10. land lO-voltpk-pk, 60Hz, calibrated square
wave outputs.
Do not connect the CALIBRATOR output to the Spectrum
Analyzer RF Section INPUT jack.
Figure 3-1. Model 141S Controls
3-2
02639-1
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Model 141S
3-18. OPERATING CONSIDERATIONS.
Note
The following sections apply to the Model
141S in all types of operation. Always allow
at least 15 min ute s war m up be for e
attempting to use the Model141S.
3-19. DEFINITIONS.
3-20. Several words and phrases, the definition of
which may vary slightly from common usage are used
to describe the operation ofthe Model 141S. The defi-
nitions of these words and phrases which apply to the
Model 141S are as follows:
a. WRITE - To transform a n input s i g n a 1 into
visible display on the CRT screen.
b. PERSISTENCE - The length of tim e a single
sweep-written display remains visible 0 nth e CRT
screen (INTENSITY and Sweep Time constant).
c. STORE - To retain, at red u c e d intensity, a
display which has been written on the CRT.
d. VIEW - To redisplay 0 nth e CRT screen, at
normal intensity, a stored display.
e. ERASE - To remove all displays and blooms
which have been stored, or written with persistence
on the CRT.
f. INTENSITY - The brightness of a display as
it is written on the CRT screen (PERSISTENCE and
Sweep Time constant).
g. BLOOM - A visible,non-symmetrical expansion
of a display written on the CRT screen. (Figure 3-5.
h. FADE POSITIVE - Appears a s random green
areas on a dark background in MAX. PERSISTENCE.
(Figure 3-7.)
i. BACKGROUND ILLUMINATION - Agreencloud
of illumination visible on the CRT screen. (Figure 3-3.)
j. SWEEP TIME - The tim e (in seconds, milli-
seconds, or microseconds) required for the beam to
move horizontally one unit of distance across the CRT
screen, when writing a display.
k. FADE NEGATIVE - A condition in which a por-
tion of the trace or screen begins to dim.
m. BURN - A burnis permanent damage tothe CRT
phosphor or mesh resulting from excessive intensity
being maintained for too long a period. Phosphor burns
appear as a discolored area on the CRT screen. Mesh
burns appear as spots or traces that are darker than
the background ill u min at ion in the MAX. PERSIS-
TENCE, MAX. WRITE modes.
3-21. CONTROL FUNCTIONS.
Ea
Excessive intensity for long duration may
damage the CRT storage mesh. The IN-
TENSITY setting for any sweep speed
should be that intensity which just elimi-
nates any trace blooming with minimum
PERSISTENCE setting.
02639-1
Section III
Paragraphs 3-18 to 3-26
3-22. PERSISTENCE and INTENSITY. These controls
contribute to the duration of afterglow of a dis pIa y .
Always set PERSISTENCE and INTENSITY as shown
in Figure 3-2. The PERSISTENCE control sets the
rate at which a display is erased; INTENSITY sets
the brightness of the trace as it is written. Since the
PERSISTENCE control sets the rate of eraSing a writ-
ten display, it follows that a brighter trace will requirE
more time to be erased. Conversely, a dis pIa y of
low intensity will disappear more rapidly. The same
principle applies to a stored display of high 0 r low
intensity.
3-23. PRESENTATION SELECTOR. This control
selects the mode in which the CRT functions. In the
ERASE position, the other three functions are dis-
connected and all stored and persisting displays are
removed from the CRT. The WRITE pOSition is the
only position on the selector in which a display may be
written on the CRT screen. The STORE position dis-
connects the WRITE function and retains written dis-
plays (at reduced intensity) on the CRT. INTENSITY
and PERSISTENCE do notfunction in the STORE posi-
tion. The VIEW position intensifies the stored display
to a set brightness. Again,INTENSITYandPERSIST-
ENCE do not affect the display.
3-24. WRITING RATE. Inthe MAX position, the rate
of eraSing a written display is decreased. Since the
eraSing rate is decreased, the entire screen becomes
illuminated more rapidly and the display is obscured.
The effective perSistence and storage time are thus
considerably reduced.
3-25. OPERATING TIPS.
3-26. These operating tips will provide the operator
with a familiarity with instrument controls and aid in
obtaining desired CRT display.
a. The perSistence uniformity inNORMALwriting
rate can be considerably improved by reducing the
size of the usable display area. To accomplish this,
ref e r to Paragraph 5-20, w, except that the inner
green rings may be moved in as much as one inch.
b. For variable perSistence operation, use mini-
mum INTENSITY and maximum PERSISTENCE com-
patible with the desired display. (See Figure 3-4. )
c.
Use WRITING RATE in MAX only for fast sweep
time, single- shot displays, or to improve the uniform-
ity of trace intensity. The MAX position causes more
rapid positive fading on the CRT and perSistence or
storage time of the display is thus reduced.
d. To store a display, set the PresentationSelec-
tor to WRITE, adjust the INTENSITY and PERSIST-
ENCE for the desired display and rotate the presenta-
tion Selector to STORE.
e.
To view a stored display, rotate the Presenta-
tion Selector to VIEW.
f. To store more than one display, set Presenta-
tion selector to V1RlTE, set PERSISTENCE fully clock-
wise and INTENSIT Y as required; allow first display
to be written on the CRT. Set INTENSITY fully counter-
clockwise and connect second Signal to be stored. Re-
set vertical POSITION if second display is not to be
superimposed 0 n first. Slowly rotate INTENSITY
3-3
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Section III
Figure 3-2
4 3 5 2
Model 141S
14IS-A-4
VARIABLE PERSISTENCE MODE NORMAL
PER$STENCE MODE
1. R otate WRITING RATE to NORMAL position.
1. Rotate WRITING RATE to NORMAL position.
2. Rotate Presentation Selector to WRITE.
2. Rotate Presentation Selector to WRITE .
3.
Rotate PERSISTENCE control ccw to, but not
in, NORMAL
detent.
3. Rotate PERSISTENCE control ccw to, but not
in, NORMAL detent.
4. Adjust INTENSITY to a point where no trace
blooming appears.
4. Adjust INTENSITY to a point wh ere no trace
blooming appears.
5. Set PERSISTENCE fully ccw into NORMAL de-
tent. 00 NOT INCREASE INTENSITY.
3-4
Trace blooming, Figure 3-5, is the best indicator of exces-
sive INTENSITY which can damage the CRT. However,
blooming does not occur when PERSISTENCE is set to NOR-
MAL. Therefore, 00 NOT INCREASE INTENSITY WHEN
PERSISTENCE IS SET TO NORMAL. Always be sure to re-
peat above procedure each time sweep speed or input sig-
nals change. -- --
Figure 3-2. Proper Intensity Adjustment.
02639-1
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Model 141S
clockwise until second display appears. Rotate Presen-
tation Selector to STORE and both displays are stored.
g. A display stored when instrument powe l' is turned
off, will remain stored for several days. To observe
a stored display, set Presentation Selector to VIEW
and vertical POSITION control ccw, before turning on
the Model 141S.
h. To erase all perSistent or stored displays, set
Presentation Selector to WRITE and rotate PERSIS-
TENCE control counterclockwise to (but not in) NOR-
MAL detent; or rotate Presentation Selector to ERASE
for approximately 1 second, then release. ( Fir s t
method not effective when WRITING RATE is set to
MAX.)
i. When using the Mode 1 141S for single sweep
operation, the FOCUS control must be adj usted indi-
rectly to obtain a well-defined trace. Set the sweep
for single operation, erase the CRT, trigger the sin-
gle sweep and note trace definition. Change FOCUS
setting as necessary each time and repeat preceding
until sharpest trace is obtained.
j. If only a portion of a slow sweep display is de-
sired, switch the Presentation Selector to STORE
when the trace has been written to the desired point;
the write gun is blanked and the written portion is
stored.
k. Use a viewing hood, if desired, to improve
screen-display contrast.
Figure 3- 3. Background illumination occurs when
eraSing with WRITING RATE in MAX
Figur e 3- 5. Single-shot trace bloom caused by
INTENSITY
and / or PERSISTENCE set too high
02639-1
Section III
Paragraphs 3- 27 to 3-28
m. If high intensity is us ed to write a trace on the
CRT, it may not completely era s e with one ERASE
operation. Continue to erase the CRT in the normal
manner taking care not to keep the Presentation Se-
lector in ERASE for more than 1 sec o n:! at any 0 n e
time.
n. Fi gures 3-3 through 3-10 are provided to show
typical CRT di splays with various control settings and
input signals. They are examples which , if duplicated
by the operator, will aid in understanding the operation
of the Model 141S. Figure 3-10 shows small bright
spots on the CRT screen which are ca used by minute
imperfections in the storage mesh.
3·27. SINGLE·SHOT OPERATION.
3-28. To write with persistence or store a single-
shot phenomena, trial setting ofINTENSITYis the best
approach . The amplitude of the phenomena and the
sweep -ti me required to display it will affect the per -
sistence. For example, with maximum PERSISTENCE
and some settings of INTENSITY, a s ingle - shot
straight-line trace may bloom, Figure 3-5, and a
Single-shot signal with amplitude variations of several
diviSions may not c au s e blooms, Figure 3 - 6. To
determine the be s t INTENSITY setting, connect a
signal which approximates the sweep time and ampli-
tude of the single - shot signal to be w ri t ten. Set
PERSISTENCE fully clockwise and trigger a s in gle
sweep of the test signal. Set the INTENSITY as far
c lockwise as possible without causin g blooming.
Fi g ure 3- 4. Variable persistence with a slow,
repetitive sweep
Fi gure 3-6. Single-shot displa y with INTENSITY
and PERSISTENCE set the same as Fi g ure 3-4
3-5
. ------------ ------ ------ -------- ------------------------------------------------------ -- -------------------------- -
Scans by Artekmedia => 2010
ArtekMedia
Digitally signed by ArtekMedia
DN: cn=ArtekMedia, o=ArtekMedia.com, ou,
[email protected], c=US
Date: 2010.12.07 11:12:22 -06'00'

Section III
Paragraphs 3-29 to 3-31
Figure 3-7. Fade positive which occurs after
Presentation Selector is left in VIEW
for 2 to 4 minutes
Figure 3-9. Same display as Figure 3-8 after 3
minutes in VIEW
Repeat the s ingl e sweep signal, erasing the display
and setting the INTENSITY after each trace until the de-
sired display is obtained. This setup should give maxi-
mum persistence tot h e Single-shot display. After
the Single-shot signal has been written, turn the
Presentation Selector to STORE to retain the display.
3-29. Single- shot signals which require a sweep time
faster than 20 microseconds per division can be
written with more brightness by setting the WRITING
RATE to MAX. The screen will be unevenly illumin-
ated after erasing when WRITING RATE is in MAX,
however the INTENSITY can be set high enough to make
the display visible through the illumination . A display,
written with WRITING RATE set to MAX, will be ob-
scured by positive fading more rapidly than a display
written with WRITING RATE set to NORMAL.
3-30. Single-shot Signals whi ch requ ir e a sweep time
between 20 and 200 microseconds per centimeter may
3-6
Model l41S
Figure 3-8. Single-shot 20 J..Lsec / cm display
Figure 3-10. Small bright spots caused by minute
imperfections in storage mesh
have low brightness at the center of the screen. Fire
a single- shot test Signal with INTENSITY and PERSIST-
ENCE fully clockwise and WRITING RATE in NOR-
MAL, and if the center brightness is low, wait for one
to three minutes for the low- brightness area to become
brighter. Likewise , if the entire display brightness
appears below a usuable level, or the display is not vis-
ible at all, wait for one to five minutes for the display
to appear, Figures 3-8 and 3-9.
3-31. For Single- shot Signals requiring a sweep time
fro m 0 n e to five minutes, set PERSISTENCE and
WRITING RATE to NORMAL and INTENSITY as re-
quired to prevent blooms. Fire the Single-shot Signal
and after the sweep is completed, rotate Presentation
Selector to VIEW and PERSISTENCE out ofNORMAL.
The complete display may then be viewed for up to one
minute or stored (Presen tati on Selector to STORE)
for up to one hour.
02639-1
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r
Model 141S
Section IV
Paragraphs 4-1 to 4-10
SECTION IV
PRINCIPLES OF OPERATION
4-1. FUNCTIONAL DESCRIPTION.
4-2. Refer to the block diagram, Figure 4-1, for
this explanation. The Model 141S Display Section has
five main circuits: a low-voltage supply, a high-voltage
supply, calibrator circuit, pulse circuit andcompe~sa
tion attenuator circuit. The horizontal and vertIcal
amplifier circuits are in the plug-in units and operate
directly into the CRT.
4-3: LOW-VOLTAGE SUPPLY. The Low -voltage
supply uses 115 or 230 volts ac (rear panel switch),
single phase, 50-60Hz. Output voltages are +100,
-100, +250
and -12.6 volts dc; all outputs are fused and
are electronically regulated. Voltages are distributed
to the high-voltage supply, the calibrator, pulse cir-
cuit, compensation attenuator circuit, and to the hori-
zontal and vertical plug-ins. 6. 3Vac is supplied from
the low voltage transforme:r: to the main filament ofthe
CRT and as a signal to the calibrator.
Do not connect calibrator output to Spec-
trum Analyzer plug-ins.
4-4. CALIBRATOR. The 6.3 Vac appliedtothe cali-
brator circuit is shaped into a square wave (of line
frequency) and applied to two front panel connectors,
lOV and IV (peak to peak amplitude). The I-volt out-
put is a 1s 0 supplied to the vertical and horizontal
plug-ins for sensitivity calibration. Accuracy of the
calibrating signal is ±1 %.
4-5. HIGH VOLTAGE SUPPLY. A transistorized
oscillator and a step-up transformer are used to gen-
erate negative and positive high voltages for the CRT.
Both the +5000 volt and -2350 volt supplies are elec-
tronically regulated.
4-6. PULSE CIRCUIT. T his c i r cui t generates a
pulse of variable level and WIdth. The pulse and other
dc voltages from the circuit are applied to the storage
and persistence elements in the CRT. All voltages
from the low-voltage supply are used in the pulse
circuit.
4-7. COMPENSATION ATTENUATOR. A compensa-
tion attenuator network is added to the Model141S
between the outputs 0 f the horizontal and vertical
deflection systems and the CRT deflection plates. Re-
fer to paragraph 4-47 for a discussion of this circuit.
4-8. CIRCUIT DESCRIPTION.
4-9. lOW-VOLTAGE SUPPLY.
4-10. The low-voltage supply consists of: +100 volt
supply, -100 volt supply, +250 volt supply and -12. 6
,---------"]
115/230
VOLT
POWER
INPUT
LOW VOLTAGE 1-"16;..:.:.:3..:.V..:.AC=--_+_2_50--...:.V_+_10_0_V_-~10_0_V_-_12_._6V ___ """i-_.,: HORIZONTAL ,
POWER SUPPLY
UNBLANKING I PLUG -IN '
~~~~~--4-------r1-~, ,
1 PERSISTENCE 1 L
____ ] ____ ...J
HIGH VOLTAGE
PULSE
CIRCUIT
I
I
o
/
r\ PRESENTATION
U SELECTOR
>-----1 POWER SUPPLY 1----------1
1FOCUS 16 i :
1 ASTIGMATISM 16 6 1 INTENSITY 1
TRIGGER
CONNECTION
r---- -----,
I :
VERTICAL
PLUG -IN
: ,
'- _________ ...J
'-----i COMPENSATION
ATTENUATOR
Figure 4-1. Model 141S Block Diagram
1---0
'r----,
l"'IS-8-1
02639-1
~.----~
4-1
Scans by Artekmedia => 2010

Section IV
Paragraphs 4-11 to 4-19
volt supply. The +100 volt supply is independent, and
provides a reference voltage for the -100 volt supply.
the +250 volt and -12.6 volt supplies are dependent on
the -100 volt supply for reference voltages.
4-11. Figure 4-2 is a simplified block diagram of
regulator used in the low-voltage supply. The series
regulator acts as a variable resistance in the regulated
output. A sen sor (or differential amplifier) compares
the output voltage with a reference voltage (dc return
for the supply). The driver (emitter follower or
amplifier) controls the bias on the series regulator,
which effectively controls the series resistance. Any
change in output voltage is fed back to the series regu-
lator. The change in series resistance and the result-
ing voltage drop is opposite to the 0 u t put v 0 It age
change; t h us the output voltage is maintained at a
constant level.
4-12. Figure 5-7 is a schematic diagram of the low
voltage supply. The primary winding of transformer
T401 is wired through a rear panel switch for quick
conversion to either 115 or 230 Vac operation. Line
voltage is applied to the primary of T401 through an
on-off switch, a fuse and a thermal switch. A pilot
lamp is provided to indicate when power is applied to
T401. Two shunt resistors are connected to the +250
volt supply to reduce serie s regulator powe l' diSSipation
when high-current plug-ins are used. The shunts are
wired one to each rear panel plug and the internal
wiring of the plug-in determines whether the shunt is
or is not used.
4-13. +100 VOLT SUPPLY. The ac voltage from secon-
dary of T140is rectified by CR441-CR444 and partially
filtered by C441 and R44l. The resulting dc voltage is
applied through the Series Regulator, Q441, to the out-
put. Differential Amplifier, Q447/Q448 compares the
voltage across R447 and V441 with a sample of the
output voltage. Any tendency of the output voltage to
change is applied to the base of the Driver, Q442,
which controls bias on Regulator, Q44l. Series Regu-
lator compensates for the change in output voltage by
its change in series resistance and restores the out-
put level to normal. The +100 volt output is adjusted
by R453. Fuse F441 provides overload protection.
4-14. -100 VOLT SUPPLY. Reference voltage for the
-100 volt supply is taken from the output of the +100
SERIES
REGULATOR
UNREGULATED
DC FVROOL~AGE _
RECTI FIERS
r
DR I VER
REGULATED
DC OUTPUT
SENSOR
OR
DIFFERENTIAL
ANPLIFIER
L_
REFERENCE
VOLTAGE
Figure 4-2. Regulated Power Supply Block Diagram
4-2
Model 141S
volt supply. The reference voltage across R467 is
compared with a sample of -100 volt output across
R473. The error voltage sensed by Differential Amp-
lifier, Q463/Q464, is applied through the Driver, Q462,
and Series Regulator Q461. Series Regulator brings
the -100 volt supply back into proper balance with re-
spect to the +100 volt supply. AC voltage from T401
is rectified by CR461-CR464, partially filtered by
C461/C462/R461, and the resulting dc voltageisap-
plied by the Series Regulator Q461, to the -100 volt
output. Regulation is obtained as in the +100 volt sup-
ply. R471 adjusts the -100 volt output and fuse F461
provides overload protection.
4-15. +250 VOLT SUPPL Y. Sensor Amplifier, Q423,
in the +250 volt supply senses any variation in the out-
put voltage, with respect to -100 volts. The error
voltage is amplified by Driver, Q422, which applies
cor l' e c t i v e bias to Series Regulator, Q421, R432
adjusts the +250 volt output and fuse F421 provides
overload protection. CR427 provides temperature
compensation for Q423 and is normally forward- biased.
4-16. 12.6 VOLT SUPPLY. Sensor Amplifier, Q484
senses any variation of output voltage with respect to
-100 volts and applies the error voltage to Driver
Amplifier, Q482. The Driver increases signal current
tothe level required to control Series Regulator, Q481.
The -12.6 volt output is adjusted by R488. Current
Limiter, Q483, a protective circuit for the Series
Regulator, is normally biased off. If an overload occurs
across the -12. 6 volt output, the base of Q483 goes
positive by the voltage drop across R483 minus the
forward breakdown voltage of CR483, thus turning
Q483 on. The decreased positive voltage on the col-
lector of Q483 is applied through Q482 to the base of
Series Regulator, Q481 reducing current flowing
through Q481. The current which then flows through
the overload is limited to the current required to keep
Q483 on. Additional overload protection is provided
by fuse, F481.
4-17. CALIBRATOR.
NOTE
Calibrator must not be connected to INPUT
of Spectrum Analyzer plug-ins. Damage to
RF Section will result.
4-18. The schematic diagram of the Calibrator cir-
cuit is shown in Figure 5-14. The circuit consists of
three parts: a tunnel diode square wave generator, a
transistor switch, and a calibration network.
4-19. 6. 3 volts ac is applied through R491 to tunnel
diode CR490, which generates a square wave at line
frequency. Transistor switch Q490 is off during the
time of the positive half-cycle ofthe square wave (when
the voltage at the base is close to zero), and the col-
lector voltage is thus at a level set by dc voltage
divider R493, R495, and R496. When the negative-
going portion of the square wave is applied to the base
of Q490, the transistor conducts heavily, effectively
shorting the collector to ground. The output of the
Calibrator is thus zero volts. At the end of the nega-
tive input half-cycle, the bias of Q490 returns to zero,
the transistor is switched off, and the output returns
to its previous value.
02639-1
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Model 141S
+RECTIFIER
,--.
DOUBLER
CR606/CR607
HIGH ~LTAGE
TRANSFORMER
T601
-RECTIFIER
~
V604
OSCILLATOR
Q602
~
-RECTIFIER
CR60B
REGULATOR
Q601/V601
'.I' HIGH
/0
VOLTAGE
ADJUST
-
A
~
(
(
,-
IINTENSITYI
IFOcusl
Section IV
Paragraphs 4-20 to 4-29
/
-)
D
T RACE
L1GN A
~
~
- --
-- -
~
---4T'I
-AXIS
NPUT
1415-6-2
Figure 4-3. High Voltage Power Supply Block Diagram
4-20. Tunnel diode bias current is supplied through
R492. The bias current sets an operating level for the
diode which affects the symmetry of the square wave
output. Cal Adj, R494, is used to set the dc voltage at
the collector of Q490 to -10 volts when the transistor
is off. Breakdown diode CR491 reduces the output
impedance, and provides tern per at u r e compensa-
tion for the circuit. Voltage divider R495/R496, re-
duces the 10 volt output to 1 volt. Both 10 volt and 1 volt
outputs are available on the front panel of the Model
141S and the 1 volt output is available to bot h plug-ins.
4-21. HIGH- VOLTAGE SUPPL Y.
4-22. Figure 4-3 is a block diagram ofthe high-voltage
supply. The output of a regulated transistor oscillator
is stepped up in voltage and applied to a series of high
voltage rectifiers. The positive output of the voltage
doubler is connected to the post-accelerator ofthe CRT.
The negative output voltages are used in the gun assem-
bly ofthe CRT and its associated controls. The Z-axis
input can be used to apply intensity modulating signals
to the CRT.
4-23. Figure 5-11 is a schematic diagram ofthe high-
voltage supply and the CRT. Oscillator Q602 operates
at a frequency of approximately 32 kHz. Any change
in the output voltage is applied to the grid of V601,
which converts the voltage change to a current change.
This current change is applied, by Emitter Follower
Q601, to the base of the oscillator transistor. The
amplitude of oscillations is changed in such a direc-
tion as to oppose the original output voltage change.
High- Voltage Adjust R619 sets the amplitude of oscil-
lation to produce the correct output voltage.
4-24. Two separate negative supplies are used, one
for the control grid of the CRT, and one to provide
CRT cathode focusing voltages. Both supplies
02639-1
l----
use half wave rectifiers (V604 and CR608). The un-
blanking gate from the horizontal plug-in (pin 1, J2)
is applied to the return side of the grid supply and
changes the negative grid voltage by about +50 volts
to unblank the trace. A positive pulse of about 20
volts will blank the trace when applied to Z-axis in-
put. When Z-axis input is not used, set S601 to INT
to receive chopped blanking from a dual trace plug-in.
4-25. The voltage doubler circuit provides the 5 kV
post-accelerating voltage applied to the CRT.
4-26. The ASTIGMATISM adjustment, R461, affects
the roundness of the spot, and the Geometry adjust-
ment, R643, is used for best pattern shape.
4-27. STORAGE CRT.
4-28. Refer to Figure 5-11 for the schematic diagram
of the storage CRT, V 610. The CRT contains the con-
ventional electron (w r it i n g) gun, deflection plates,
post-accelerator, and phosphor screen. In addition,
there are two flood guns (filaments, cathodes, and
grids only), a collimator, a collector mesh and a
storage mesh. These added elements make possible
the variable perSistence and storage functions of the
Model14lS
4-29. FLOOD GUNS. The flood guns are physically
located on the electron gun outside of the horizontal
deflection plates. Horizontal Drivers, Q603, and
Q604prevent flood gun electrons from flowing through
the deflection plate s to the output stage of the plug-in.
The gun operates continuously when the power switch
is on. An electron cloud, which is emitted by the flood
guns, is accelerated toward tm CRT screen by colli-
mator and collector mesh voltages. These electrons
make stored or persisting displays visible. They are
also used to erase stored and persisting displays.
4-3
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Section IV
Paragraphs 4-30 to 4-38
4-30. COLLIMATOR. The collimator is aninternal
coating along the taperedportionofthe CRT. A posi-
tive voltage applied to the collimator focuses the flood-
gun electrons. The cloud electrons are formed into a
column perpendicular to, and approximately equal to
the diameter of, the CRT screen.
4-31. COLLECTOR MESH. The collector me s h is
between the flood guns and the storage mesh (closest
to the storage mesh). It is always positive with re-
spect to the storage mesh except in the ERASE position
of the Presentation Selector; both are then at the same
potential. In addition to accelerating flood gunelec-
trons, the collector mesh also repels positive ions
generated by the flood guns.
4-32. STORAGE MESH. The storage mesh is just
behind the CRT screenandis coated with non-conduct-
ing material. It is statically held at a slightly positive
potential (approximatly +3 volts). When the electron
beam from the writing gun strikes the mesh coating,
secondary electrons are emitted. T hi s secondary
emission creates a pattern of positive potential iden-
tical to the movement of the beam. Flood gun electrons
are accelerated by this positive potential pattern and
strike the phosphor screen, thus creating a visible
display.
4-33. The storage mesh is continuously pulsed with a
variable width pulse of approximately -11 volts. These
pulses erase the positive pattern on the storage mesh
by discharging the mesh coating. Time required for
this erasing operation is determined by the width of
the negative pulse. The positive pattern on the mesh
may also be neutralized manually by connecting the
collector and storage meshes (ERASE). The highposi-
tive potential (approximately +156 volts) allows more
uniform discharging of the surface. When the storage
mesh is disconnected from the collector mesh and re-
turned to +3 volts, the coated surface is at a uniformly
equal potential of -9 volts. In both cases, the screen
has no illumination. The pattern may be lost by the
storage mesh fading positive and allowing the entire
screen to be illuminated. This occurs when positive
o
Model 141S
ions from the flood gun raise the surface potential of
the storage mesh in random areas sufficiently to allow
flood gun electrons to strike the screen.
4-34. PULSE CIRCUIT.
4-35. Figure 4-4isa simplified block diagram of the
Pulse Circuit. A free running Multivibrator triggers
a Monostable Multivibrator. The pulse width of the
Monostable Multivibrator is varied by the setting of
the PERSISTENCE control. The output of the Mono-
stable Multivibrator is applied to the CRT storage
mesh in the WRITE mode to control the display per-
sistence. In STORE, the Monostable Multivibrator
output is amplified and applied to the CRT collimator.
4-36. Figure 5-14 is a schematic of the Pulse Circuit.
The Multivibrator Q701/702 free-runs at approximately
1200 Hz. The square wave output is differentiated
by C703. The negative spike is blocked by CR701 and
the positive spike is applied to Q703. The positive
spike turns Q703 on and C705 couples a negative-going
signal through 0704 to start turning Q705 off. Q704,
an emitter follower, isolates the variable load of the
PERSISTENCE control from Q705. The turning off
of Q705
generates apositive-going signal at its collec-
tor. R708 couples this signal to Q703 driving it to
saturation. C705 is now charged to -11 volt and begins
to discharge toward ground through R730 and the
PERSISTENCE control. When C705 reaches approxi-
mately -9. 5 volts Q705 begins turning on. When Q705
turns on a negative-going signal is coupled through
R708 to 0703 turning it off. C705 then continues to
discharge to ground through R730 and the PERSIST-
ENCE control in parallel.
4-37. The WRITE functionofthe Presentation Selector
allows the Model 141Stobeused as a normal or vari-
able perSistence oscilloscope.
4-38. The STORE function ofthe Presentation Selector
allows the Modell4lS to store a previously written trace
for periods of one hour or more at reduced intenSity.
In this position of the Presentation Selector the negative
pulses from Q706 are amplified bya normally-off two
LEVEL ~
ADJ .,.
~ PULSE AMPL
T ADJ
I 1 1
I 1 1 I
I
MULTIVIBRATOR
MONOSTABLE
0701/0702
MUL TIVIBRATOR
0703-0706
1 1 I
I 1 I
1 1 1
: L------O------J
6
'
PRESENTATION
SELECTOR
I PERSISTENCE I
Figure 4-4. Pulse Circuit Block Diagram
4-4
TO CRT
PULSE
AMPLIFIER
TO CRT
0707/0708
1
1
1
1 I
I 'i FLOOD GUN
I 1
ADJ
I ~ COLLIMATOR ADJ
';'STORAGE COLLIMATOR
ADJ
14IA-8-2A
02639-1
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