Hewlett-Packard 181 A, 181 AR Oscilloscope OPERATING AND SERVICE MANUAL

 OPERATING AND SERVICE MANUAL
SERIALS PREFIXED:840
See Section VII for Instruments With Other Serial Prefixes
Copyright HEWLETT-PACKARD COMPANY/COLORADO SPRINGS DIVISION 1967
1900 GARDEN OF THE GODS ROAD, COLORADO SPRINGS, COLORADO, U. S.A.
02612-4 o PRINTED: APR 1969
Section I | | Model 181A/AR
Table 1-1
> Table 1-1. Specifications.
HORIZONTAL AMPLIFIER | OUTPUTS
| | External Input | Four emitter follower outputs for main and delayed
| Bandwidth: de coupled, de to 5 MHz; ac coupled, gates, main and delayed sweeps. Maximum cur-
О 5 Hz to 5 MHz. rent available is +3 ma. Outputs will drive imped-
- Deflection Factor (sensitivity): 1 v/div, +5% on ances down to 1k ohm without distortion,
X1; 0.2 v/div £5% on X5; 0. 1 v/div 5% on | |
X10; vernier provides continuous adjustment GENERAL
between ranges. Dynamic range +5 v. | : | |
Input RC: 1 megohm shunted by approximately Active Components: all solid state (no vacum tubes
30 pf. except CRT).
Sweep Magnifier: X1, X5, X10; magnified sweep | Environment: Model 181A/AR Oscilloscope with
| accuracy +5%, | plug-ins operates within specifications over the
> | | | following ranges; |
CALIBRATOR | В | о | — Temperature: 0° C to +55° C.
| | | | | Humidity: to 95% relative humidity to 40° C.
Type: approximately 1 kHz square wave, less than | Altitude: to 15,000 ft.
.3 u sec rise time. | Vibration: vibrated in three planes for 15
Voltage: 10v peak- -to-peak, +1%, - | min each with o. 010 inch excursion, 10
| to 55 Hz,
CATHODE RAY TUBE AND CONTROLS Power: 115 or 230 volts, +10%; 50-400 Hz, 100
— watts at normal line, convection cooled,
Type: post-accelerator storage tube; 8.5 kv.ac- | Dimensions: cabinet (overall dimensions) 8" (203)
celerating potential, aluminized P31 phosphor. wide, 11" (280) high, 22-1/2" (570) deep.
Graticule: 8 x 10 division parallax-free internal Rack Dimensions/ Model 181AR: |
graticule marked in . 95 centimeter squares. | |
- Subdivisions of 0.2 div on major axes. Front - ors. METRO ts ur
| | panel recessed TRACE ALIGN alignstrace with — © SEE HSE a CHE moe
am, ~~ graticule. Y axis may be aligned to be perpen- REA APN RE | |
( - dicular with X axis with internal control for ac-
“es j curate rise time measurements. TOP o 28
| Writing Rate: Write mode; 20 em/msec 1093; 19
Max write mode; 1 em/ sec |
Erage: push-button erasure takes approximately |
‚300 msec.
Brightness: greater than 200 foot/lamberts with |
entire screen faded positive. CB ee m
i Persistence: continuously variable from less than REAR -
0. 2 second to more than one minute, or normal | f
P31 persistence of approx 40 u sec. | | О | | 1BOA-A-1000
: Storage Time (MAX W) Mode: ten minutesis STORE" . |
| mode, ten seconds in VIEW mode. | | |
‘Beam finder: pressing FIND BEAM control when — Weight: {without plug-ins} Model 181A; Net, 24
‘operating in any mode except STORE or VIEW lbs (10,9 kg); Shipping, 32 lbs (14,5 kg). —
brings trace on CRT screen regardless of set- Model 181AR (rack); Net, 26 Ibs (11,8 kg);
ting of horizontal or vertical controls. . Shipping 35 lbs (15,9 kg). |
intensity Modulation: approximately +2 volts, de | Accessories Furnished mesh contrast filter, de.
to 15 MHz, will blank trace of normal intensity. | tachable power cord, rack mounting hardware, |
Input resistance is 5100 ohms. (rack model only),
1-0 a | a = 02612-3
Model 181A/AR
Section I
Paragraphs 1-1 to 1.5
SECTION |
GENERAL |
1-1. DESCRIPTION.
1-2. The Mode! 181A/AR, Figure 1-1, isa lightweight,
general purpose, variable persistence, storage oscil-
loscope with plug-in capability, The Model 181A and
the Model 181AR as shipped from the factory are in-
tended for bench use. The Model 181AR may be rack
mounted as described in Section II,
1-3. Except for the CRT, all active components are
solid state devices. The Model 181A/AR is convec-
tion cooled and operates within specifications over a
temperature range of 0° C to +55” C.
NFORMATION
1-4, The variable persistencecapability is especially
useful for viewing slow-speed signals. Adjustment of
persistence time can provide viewing of a complete
trace with fading sufficient to prevent interference
with the next trace. The display persistence canread-
ily be adjusted to eliminate flicker and still provide
high resolution,
1-5, The storage feature of the hp Model 181A/AR
canbeusedto store single-shot occurrences for later
viewing or photographing. Comparison of waveforms
can be accomplished by storing several separate oc-
currences and later viewing them simuitanecusiy.
HE
ER
aid
en
ee
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Figure 1-1. Model 181A and 181AR Oscilloscopes
02612-2
TEA,
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Section
Paragraphs 1-6 to 1-24
1-6. The horizontal amplifier has a direct-coupled
bandwidth of de to 5 MHz. The ac-coupled bandwidth
is 5 Hz to 5 MHz, With a dynamic range of +5 volts,
the amplifier has front-panel selectable deflection
ranges of 1 v/div, 0.2 v/div and 0. 1 v/div. A vernier
control provides continuous adjustment between ranges.
A magnified sweep accuracy of 5% is maintained at
selectable magnifications of X1, Xb or X10; and a front
panel BNC connector permits the use of external de-
flection signals. The external input has an input im-
pedance of 1 megohm shunted by approximately 30 pi.
1-7. A rear panel BNC connector is provided for ex-
ternal control of CRT blanking. A signal of approxi-
mately +2v from de to 15 MHz will blanka {race of
normal intensity. The input resistance is 5100 ohms.
1-8. External outputs are provided through four rear
panel mounted BNC connectors for coupling plug-in
derived signals to external equipment. Since these
outputs are dependent upon the plug-ins utilized, the
appropriate plug-in Operating and Service Manual
should be referred to for identification of the output
signals available. The output amplifiers can supply
3 ma, and will drive impedances as low as 1000 ohms
without distortion,
1-9. А 1 kHz square wave signal is available at the
front panei for calibration purposes. Its amplitude of
10 volts peak-to-peakis accurate to +1%, and it has a
rise time oflessthan3xu sec. The signal may be used
toadiusthorizontal and vertical deflection factors and
to compensate divider probes.
1-10. CATHODE RAY TUBE.
“1-11, The Model 181A /AR uses an internal graticule,
P31 aluminized phosphor CRT. Special internal ele-
ments provide the variable persistence and storage
features. Parallax observation error is eliminated
by use of the internal graticule, and a non-glare safety
face plate is bonded to the CRT.
1-12. WARRANTY.
1-13. This instrument is certified and warranted as
described on the inside front cover of this manual.
The CRT is covered by a warranty separate from the
rest of the instrument. The CRT warranty and war-
ranty claim forms are located at the rear of this manual.
Should the CRT fail within the time specified on the
warranty, contact vour nearest hp Sales/Service
Office, and return the CRT with the warranty form
completed. |
1-14. ACCESSORIES FURNISHED.
1-15. The standard Model 181A/AR Oscilloscope is
supplied with a mesh contrast filter, and a detachable
Model 181A /AR
power cord. Also included with the Model 181AR is
a rack mounting kit.
1-16. ACCESSORIES AVAILABLE.
1-17. À mobile test stand for the cabinet Model 181A
is available. The Model 1118A Tesimobile provides
adjustable height, tilt,and rotation. Equipped with
locking wheels, itis readily collapsible for {ransport.
Anadapter assembly, available as hp Part No. 01118.
69501, permits the rack Model 181AR to be mounted
on the Model 1119A Testmobile,
1-18. A front panel cover of fiberglass material, hp
Model 10166A, canbe usedto provide {ront panel pro-
tection for the cabinet Model 181A, and a cover for
the rack Model 181AR is available as hp Part No.
5060-0437,
1-19, For ease of calibration and maintenance an hp
Model 10407A Plug-in Extender can be obtained. И
provides for removal of the plug-ins from the main
frame and exposes components and adjustments,
1-20. Cameras, probes, viewing hoods, terminations
and other accessory items are available for special-
ized requirements. Information on these andthe above
describedaccessories may be obtainedfrom hp Sales/
Service Offices listed in the rear of this manual.
1-21. INSTRUMENT IDENTIFICATION.
1-22. Hewiett-Packarduses a two-section, eight-digit
serial number to identify instruments. The first three
digits (preceding the dash) are the serial prefix which
identifies a series of instruments; the last five digits
identify a particular instrument in the series, The
serial number appears ona plate located on the rear
panel. All correspondence with a Hewlett-Packard
Sales/Service Office inregardto an instrument should
reference the complete serial number.
1-23. SCOPE OF MANUAL.
1-24. This manual provides operating and service in-
formation for the hp Model 181A/AR Oscilloscope.
Information and operation of plug-ins is contained in
appropriate plug-in manuals. Information in this
manual applies directly to instruments (as manufac-
tured} with serial numbers prefixed by the three digits
indicated on the title page. I the serial prefix of the
instrument ig different from that on the titie page, a
"Manual Changes’ sheet supplied, or Section VII of
this manual, will describe changes which will adapt
this manual to provide correct coverage, Technical
corrections (if any} to this manual, due to known
errors in print, are called Errata and are shown on
the change sheet, For information on manual cover-
age of any hp instrument, contact the nearest hp Sales/
Service Office (addresses are listed at the rear of
this manual).
02612-2
Model 181A/AR
Section II
Paragraphs 2-1 to 2-17
SECTION H
INSTALLATION
2-1. INITIAL INSPECTION.
2-2. MECHANICAL CHECK, Check the shipping
carton for damage immediately after receipt. If itis
damaged, ask the carrier's agent to be present when
the instrument is unpacked. Inspectthe Model 181A/AR
for physical damage such as bent or broken parts and
dents or scratches. If damage is found, refer to
Paragraph 2-4 for recommended claim procedure. В
the Model 181A/AR appears undamaged, perform the
electrical check (Paragraph 2-3). Retain the pack-
aging material for possibie future use.
2-3. ELECTRICAL CHECK, The performance
check is given in Paragraphs 5-5 through 5-14. This
check will determine whether or not the instrumentis
still operating within its specifications as listed in
Table 1-1. The initial performance and accuracy of
this instrument are certified as stated on the inside
front cover of this manual. If the Model 181A/AR
does not operate as specified, refer to Paragraph 2-4
for the recommended claim procedure. Prior toíniti-
ating any performance check, refer to Paragraphs
2-10 through 2-14 andthe operating guidance provided
in Section III.
2-4, CLAIMS.
2-5. H physical damage is found or if the instrument
is not within specifications when received, notify the
carrier andthe nearest Hewlett-Packard Sales/ Service
Office immediately, The Sales/ Service Office will
arrange forthe repair or replacement of the instrument
without waiting for a claim to be settled with the
carrier.
2-6. REPACKAGING FOR SHIPMENT.
2-7. If the instrument is to be shipped to a Hewlett-
Packard Sales/ Service Office, attachatagto it show-
ing owner and owner's address, instrument's model
number and 8 digit serial number, and a description
of service required.
2-8. The original shipping carton and packaging ma-
terials, exceptfor the accordion-pleated pads, should
be used for reshipment.. If they are not available or
reusable, the instrument should be repackaged with
the following materials:
a. A double-walled carton (refer to Table 2-1 for
test strength required).
Table 2-1. Shipping Carton Test Strength
Gross Weight (ibs) Carton Test Strength (lbs)
up to 10 | 200
10 to 30 275
30 to 120 350
120 to 140 500
140 to 160 600
02612-3
b. Heavy paper or sheets of cardboard to protect
all instrument surfaces {use a nonabrasive material
such as polyurethane or a cushioned paper such as
Kimpak around all projecting parts).
с. At least 4 inches of tightly packed, industry
approved, shock absorbing material, such as extra
firm polyurethane foam.
d. Heavy duty shipping tape to secure outside of
carton.
2-9. PREPARATION FOR USE.
2.10. POWER REQUIREMENTS.
2-11, The Model 181A/AR requires either a 115 or
230 vac +10%, singie phase, 50to 400 Hz power source
- that can deliver 100 watts.
a. 115V OPERATION, "This instrument as shipped,
is ready for operation on 115 vac, See Step b below
for 230 vac operation. |
CAUTION
Before applying power, check the rear
panel slide switch for proper posiiion,
(115 or 230).
—b. 230Y OPERATION, If the instrument is to be
operated on 230 vac, setthe rear panel switch to 230.
It is not necessary to replace the 115V fuse. Position-
ing the 115/230 switch selects the proper fuse forthe
desired voltage.
2.12. THREE.CONDUCTOR POWER CABLE,
2-18. The National Electrical Manufacturer's Associ-
ation (NEMA) recommends that the instrument panel
and cabinet be grounded to protect the operating per-
sonnel. The Model 181A/AR is equipped with a de-
tachable three-conductor power cord which, when
plugged into an appropriate outlet, grounds the instru-
ment through the round offset pin. When operating
the Model 181A/AR from a two-contact outlet, use a
three-conductor to two-conductor adapter. Preserve
the safety feature by grounding the adapter lead. A
3-way grounding terminal is also provided on the rear
panel of the instrument.
2-14. INSTRUMENT MOUNTING.
2-15. BENCH USE. Both the Model 181A and the
Model 181AR, as shipped from the factory, are in-
tended for bench use, The Model 181AR, however,
may be rack mounted as described in Paragraph 2-16.
2-16. RACK MOUNTING. A kit for converting the
Model 181AR to a rack mount is supplied with each
instrument. Instructions for making the conversion
are given below. Refer to Figure 2-1 for parts iden-
tification.
2-1
e
Section II |
Paragraphs 2-18 to 2-22
Model 181A/AR
BOTTOM PANEL
De
TILT STAND
FOOT BUTTON
PLASTIC FOOT
TRIM STRIP |
ADHESiVE BACK)
-
=
rd
«>
7000HF —B-19
Figure 2-1. Berch/Rack-Mount Conversion
a, Detach tilt stand by pressing itaway from front
feet. Remove allplastic {eel by depressing metal but-
ton and sliding {eet free. BE
b. Remove aluminum trim strip from each side of
instrument with a thin blade tool.
ce. Attach rack mounting flange in space from which
trim strip was removed{use screws provided withkit).
Large notch of flange should be positioned at boito
of instrument. | | |
2.17. INSTRUMENT COOLING.
2-18. The Model 181A/AR does not need forced-air
cooling when operated in an ambient temperature of
0 to +55 degrees centigrade. Normal air circula-
tion will maintain a reasonable temperature within
the instrument. |
2-19. CONTRAST FILTER AND BEZEL REMOVAL.
2-20. A contrast filter which also acts as an RFI
shield is located behind the bezel. Use of the filter
is recommended since it provides for comfortable
viewingand RFÍ shielding, Inspecificcases, however,
such as when a camera is attached for use with the
oscilloscope, removal of the filter may be desirable.
To accomplish this, merely remove the bezel as shown
in Figure 2-2, slip the filter out, and replace the
bezel. |
2-21. To remove the bezel, grasp it as shown in
Figure 2~2A, gently apply a downwardpressure with
the index fingers until the bezel's upperearis free of
its slot, pull slightly forward and release. Next,
grasp the bezel as shown in Figure 2-2B, apply an
upward pressure with the thumbs until the bezel's
lower ear clears its slot, pull forward and remove
the bezel. Be certain to apply pressure on the inner
edge of the bezel to release the ears in both steps
since pressure on the outer edge tends to cause a
swivel action, defeating the purpose, and subjecting
the ears to possible damage.
Figure 2-2, Bezel Removal
2612-3
Model 181A/AR
Section HI
Paragraphs 3-1 to 3-16
SECTION Ii!
OPERATION
3-1. INTRODUCTION.
3-2. The Model 181A/AR is a light weight, variable
persistence, storage oscilloscope using plug-in vertical
and horizontal modules. Both high and low voltage pow-
er supplies, a calibrator, the CRT, and circuitry for
the variable persistence and storage operationare con-
tained in the Model 181A/AR. A compartment for the
horizontal and vertical plug-ins is located inthe lower
portion of the Model 181A and in the right hand portion
of the Model 181AR. In both models the compartment
is designed to accept the vertical plug-in on the left
side and the horizontal plug-in on the right. The plug-
in units must be locked together before being inserted
"into the compartment{see plug-in manuals}.
3-3. OPERATING CONSIDERATIONS.
3-4. Prior te operating the Model 181A/AR, the oper-
ator must have a thorough understanding of instrument
operation and control functions. This section should
be readinits entirety before attempting to operate the
instrument.
To avoid CRT damage, the following pro-
cedure should be followed every time the
instrument is operated.
3-5. The following are steps that must be takenprior
toapplying power tothe Model 181A/AR Oscilloscope.
a. Depress WRITE push button.
“b. Set PERSISTENCE control fully cew.
c. Set INTENSITY control fully ccw.
d. Apply power to Model 181A/AR
e. After 3 minutes, the entire CRT viewing area
should be evenly flooded green,
NOTE
If there is no green illumination, turn
instrument off and check all CRT con-
nections.
3-6. CONTROLS AND CONNECTORS.
3-7. The location of operating controis and connectors
is shownin Figure 3-1 together witha briel explanation
of their functions, Additional information regarding
some of these controls and connectors is provided below.
3-8. FRONT PANEL.
3-9. FOCUS AND ASTIGMATISM. These controlsare
provided to assure uniform focus of the trace over the
entire CRT screen. To adjust, set the Presentation
Selector to WRITE, center a low-intensity spot on the
CRT screen, and adjust FOCUS and ASTIGMATISM
02612-2
controls for a smali, round, sharply focused spot.
Readjustment of the ASTIGMATISM control is seldom
required except, for example, when the vertical plug-
in is changed.
3-10. STORE. In order to retain whatever is visible
on the CRT, depress the STORE push button. The sig-
nal will be stored at reduced intensity, resulting ina
storage time of greater than one hour. The INTENSITY,
PERSISTENCE, FOCUS, ERASE, and HORIZONTAL
POSITION contr ols do not affect the presentation in the
STORE mode.
3.11, In some applications, it maybe desirable to show
several overlapping traces at once. This is possible
through proper manipulation of the PERSISTENCE and
INTENSITY controls. Simply obtainthe desired mui-
tiple trace display in the WRITE mode, then depress
the STORE push button.
3-12. A display stored on the CRT when power is re-
moved from the instrument will remain stored for
several days. In order to observe this stored display,
depress the VIEW push button and turn the POSITION
control on the Vertical Plug-in counterclockwise prior
to restoring power to the instrument. This prevents
a bright spot from being portrayed on the screen due
to the initial surge from the CRT write gun.
3-13. Several individual waveforms may also be stored,
even thoughtheyare writtenat different times. Having
storedatrace, for instance, the operator may choose
to switchbackto WRITE and recordanothertrace, etc. ,
prior to erasing. And by turning the Model 181A/ AR
power off, as few as one trace a day can be recorded
for a week or more, depending on totaitime instrument
is turned on, as storage time would decrease accord-
ingly.
3-14. VIEW. To observe a previously stored display,
depress the VIEW push button. The stored display will
be intensified to a brightness level determined by the
intensity and persistence values selected during the
write process, Again, the INTENSITY, PERSISTENCE,
FOCUS, ERASE and POSITION controls do not affect
the display.
Excessive intensity for long duration
may damage the CRT storage mesh.
The INTENSITY setiing for any sweep
speed should be minimum usable in-
tensity.
3-15, NORMAL, Selection ofthis operating mode dis-
ables the variable persistence andstorage features of
the instrument. Itwill nowfunctionasa conventional,
general purpose, oscilloscope. The PERSISTENCE
control does not function in this mode. Always adjust
INTENSITY in WRITE mode with minimum PERSIS-
TENCE, then switch to NORMAL.
3-16. WRITE. Depressing the WRITE push button
3-1
Section HI Model 181A/AR
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Note: Models181A and 181AR differ only in power module location. Allcontrolsare identical. See Fig. 1-1.
1. FOCUS: Controls sharpness of writing beam, | 17. DISPLAY: Selects source of horizontal input
2. STORE: Retains displayed signal at reduced signal,
intensity for long time storage. 18. AC/DC: Selects AC or DC coupling of an ex-
3. VIEW: Intensifies stored display to brightness ternal horizontal input signal.
level for viewing. 19, EXT INPUT: BNC connector for coupling an
| al horizontal input signal to oscilloscope.
4. NORMAL: Selects operation as standard oscil- extern Flzomal input SIE = р
loscope. | 20. POWER: Push-button switch with indicator
ight for turning oscilloscope on and off,
о. WRITE: Operates CRT at normal writing rate light for turning ! pe on
with variable persistence, 21. CALIBRATOR: Provides a 1-kHz square
_ ; ; . a 1 T-
6. MAX WRITE: Operates CRT at maximum wave signal at 10v pk-pk.
writing rate with variable persistence. REAR PANEL
ERASE: Removes stored or written displays. A. AC INPUT: 3-wire ac power line input jack.
8. PERSISTENCE: Controls endurance time of B., MAIN GATE OUTPUT: BNC for connecting
, displayed signal. main gate to external equipment.
9. ASTIGMATISM: Adjust roundness of writing C. DELAYED GATE OUTPUT: BNC for connect-
beam. ing delayed gale to external equipment.
10. TRACE ALIGN: Rotates trace around center D, DELAYED SWEEP OUTPUT: BNC for con-
of CRT face. necting delayed sweep to external equipment.
11, FIND BEAM: Returns display to CRT, КЕ. MAIN SWEEP OUTPUT: BNC for connecting
| i to al equi t.
12, INTENSITY: Controls brightness of display. main sweep to external equipmen
Е, Z-AXIS INPUT: BNC for connecting external
intensification or blanking signal.
G. FUSE: AC line fuse for 230vac operation.
13. POSITION: Coarse adjustment of display's
- horizontal position.
14. FINE: Fine adjustment of dispiay's horizontal
position, H. FUSE: AC line fuse for 115vac operation.
15. MAGNIFIER: Magnifies horizontal display. J. LINE SWITC H: Input power switch for selec-
16. PHASE/BANDWIDTH: Selects between nor- tion of 115vac or 230vac operation.
mal operation (BANDWIDTH) and XY opera- K. GROUNDING CONNECTOR: 3-way connector
tion (PHASE). Located inside on board. jack for instrument grounding.
Figure 3-1. Front and Rear Panel Controls and Connectors.
3.2 026122
Model 181A/AR
establishes the CRT in a condition for variable per-
sistence display of a signal which can later be stored.
Use the minimum INTENSITY and maximum PERSIS-
TENCE required to obtain the desired display.
3-17. MAX WRITE. Operation in the Max Write mode
(MAX W. ) provides a more rapid build-up and display
of fast single-shot signals. Since the background il-
lumination also increases more rapidly, the CRT con-
trast level and storage time are reduced.
3-18. ERASE. Depressingthe ERASE push button will
remove stored signals from the CRT when either the
WRITE or MAX W push buttonis depressed. Stored
or written displays that remain visible after erasure,
may require the ERASE push-button be held depress-
ed for approximately 30 seconds,
3-19. PERSISTENCE ANDINTENSITY. These controls
determine the viewing time of a signal being displayed.
The INTENSITY sets the brightness of the trace as it
is written. The PERSISTENCE control is used to
establish the desired duration of signal viewing without
rewriting. Itaccomplishes this by varying the rate ai
which the displayed signal is erased.
3-20. TRACE ALIGN. The TRACE ALIGN adjustment
control compensates for external magnetic fields that
may affect the alignment of the horizontal trace with
the graticule. Thealignment should be checked when
the instrument is moved to a new location and the ad-
justment made whenever necessary.
3-21. FIND BEAM. Off-screenpositioning ofthe CRT
beam may occur due to initial improper control set-
tings or a very high dc input signal. The beam may
be brought back on screen by depressing the FIND
BEAM push button. Adjust the horizontal and vertical
position controls to center the beam (refer to the plug-
in manuals). Adjust the INTENSITY control to obtain
a visible trace.
3-22. MAGNIFIER Whenthe DISPLAY control is set
to EXT CAL, the MAGNIFIER provides switched gain
levels in the horizontal amplifier of X1, X56, or X10.
In the X5 or X10 positions, the horizontal gain is in-
creased to provide an amplified display of five or ten
times, respectively. The insertion ofa iv signal into
the EXT INPUT jack will result ina 1-division defiec-
tionin X1, 5-division in X5, anda 10-division deflec-
tion in the X10 position.
3-23. DISPLAY. This control determines the input
signal tothe horizontal amplifier. With the DISPLAY
control set to EXT CAL, the external horizontal input
signal is coupled directly to the horizontal amplifier,
As the DISPLAY control ig rotated counterclockwise,
the external signal is increasingly attenuated. When
the DISPLAY control is fully counterclockwise (INT),
the external input signal is disconnectedandthe inter -
nal sweep is coupied directly to the horizontal ampli-
fier,
3-24. CALIBRATOR. The 1kHz square-wave calibrator
output signal of 10vcanbeused for vertical sensitivity
calibration and for probe compensationadiustment. The
CALIBRATOR output amplitude is accurate within +1%.
Rise time of the square-wave output is less than 3 sec.
02612-2
| Section IH
Paragraphs 3-17 to 3-37
3.25. REAR PANEL.
3-26. OUTPUTS. Main and delayed sweep and gate
signals are available at rear panel BNC connectors of
the Model 181A/AR. These outputs are providedfrom
separate isolationamplifiers whichcan supply 3 ma and
will drive impedances as low as 1000 ohms without
distortion. The plug-ins used in the Model 1814/AR
and the control settings employed determine the out-
put signals available.
3-27. Z-AXIS INPUT. Anexternal signal can be util-
- izedfor control of CRT intensity. À rear-panel mounted
BNC connector permits a direct connectionto the CRT
intensity gate amplifier.” A signal of approximately
+2v, deto15 MHz, isrequired to blanka beam of nor-
mal intensity. Input of a negative signal c can be used
for beam intensification.
3-28. AC LINE INPUT. A three-conductor ac input
jack is providedfor power input. Also located on the
rear panel is the 115/230v slide switch andthe required
fuses for 115 vac and 230 vac operation. -
3-29. INTERNAL.
3-30, PHASE/BANDWIDTH. "The Model 181A/AR can
also be usedfor phase measurements. Positioning the
PHASE/BANDWIDTH switch to PHASE causes the
horizontal input signal to be delayedthe same amount
of time as the vertical input signal. |
NOTE
Make certain the control is returned to
the Bandwidth position after making phase
measurements. |
3-31. PLUG-IN UNITS.
3-32. The Model 181A/AR Oscilloscope requires hori-
zontal and vertical plug-ins. The deflection sensitivity
of the CRT may vary slightly with different units. Plug-
in units should be calibrated when first installed or
when shifted between oscilloscopes. The horizontal
and vertical plug-inunits must be locked together prior
to insertion intothe Model 181A/AR mainframe. Con-
sult the respective plug-in Operating and Service Man-
ual for operation and capability information,
3-33. MAGNETIC INTERFERENCE.
3-34. The CRT is providedwitha mu-metal shield for
protection against magnetic fields. Duetothe sensi-
tivity of the CRT, itis possible thatthe strong magnetic
field from nearby motors, ac line transformers, etc.
may still result ina noticeable beam deflection. In
this event, reorient or relocate the instrument with
respect to the interfering device, :
3-35. OPERATING CONDITIONS.
3-36. DEFINITIONS.
3-37. Several words and phrases, the definition of
which may vary slightiy from common usage, are used
3-3
Section IH
Paragraphs 3-38 to 3-43
to describe the operation of the Model 181A/AR. The
~ definitions of these words and phrases which apply to
the Model 181A/AR are as follows:
a. WRITE-To transform an input signal into a
visible display on the CRT screen.
b. PERSISTENCE-The length of {ime a single
sweep written display remains visible on the CRT
screen (INTENSITY and sweep time constant).
с. STORE-To retain, at reducedintensity, a dis-
play which has been written on the CRT.
d. VIEW-Toredisplay onthe CRT screen, at nor-
mal intensity, a stored display.
е, ERASE- To remove all displays, and blooms
which have been stored, or written with persistence
on the CRT.
I, 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 expan-
sion of a display written on the CRT screen.
B_ {RASA
Figure 3-2, Fade Positive and Background Illumination.
3-4
Mode! 181A/AR
h. FADE POSITIVE-Display obscured by slow
blooming, see Figure 3-24.
i. BACKGROUND ILLUMINATION-A green cloud
of illumination visible on the CRT screen, see Figure
3-28.
i. SWEEP TIME-The time {inseconds, millisec-
onds, or microseconds) requiredfor the beam to move
horizontally one unit of distance across the CRT screen,
when writing a display.
3.38. CONTROL FUNCTIONS.
3-30. PERSISTENCE ANDINTENSITY, These controls
contribute tothe duration of afterglow of a display. The
PERSISTENCE control sets the rate at which a display
is erased; INTENSITY gets the brightness of the trace
as it is written. With a given PERSISTENCE setting,
the actual duration of trace aftergiow may be increased
by increasing the INTENSITY, Since the PERSISTENCE
control sets the rate of erasing a written display,
follows that a brighter {race will require more time
to be erased. Conversely, a display of low intensity
will disappear more rapidly. The same principle
applies to a stored display of high and low intensity,
CAUTIONA
The storage mesh of the CRT is not
easily damaged, however, a high-
intensity repetitive trace or spot, writ-
ten on the screen for an extended time,
may not erase completely, To prevent
CRT damage, use minimum INTENSITY
which will give the desired display for a
given PERSISTENCE setting,
3-40, PRESENTATION SELECTION, Push button
controls select the mode in.which the CRT functions,
With ERASE push button depressed, the other three
functions are disconnectedandall stored and persist-
ing displays are removed from the CRT. The WRITE
and MAX W. modes are the only conditions in which
a display may be written on the CRT screen. The
STORE mode disconnects the WRITE and ERASE func-
tions and retains written displays (at reduced intens-
ity) on the CRT. INTENSITY, PERSISTENCE, and
ERASE do not function in the STORE mode. The
VIEW mode -intensifies the stored dispiay to a set
brightness and again, INTENSITY, PERSISTENCE,
and ERASE do not affect the display.
3-41. MAX WRITE. When MAX W. push button is de-
pressedandthen the ERASE push bution is depressed
and released, the storage surface is erased and then
primed {or pre-fogged) to allow much faster writing
on the storage surface. The display, however, has
reduced contrast and fades positive more rapidly. The
contrast and storage time are also reduced in this
mode.
3-42. OPERATING TIPS.
3-43. This information is provided toaidthe operator
in becoming familiar withthe Model 181A/AR controls
andtheir functions, andto serveas a guide for obtain-
ing the desired CRT display.
a. For normal persistence operation, depress
WRITE push button and turn PERSISTENCE control
02612-3
Model 181A/AR
Фа Пу сем. Slowly rotate INTENSITY control ew to a
point where no trace blooming appears. Depress
NORMAL push button; do not increase INTENSITY
while in NORMAL, Ifsweepspeedis changed, always
check for proper intensity using the above procedure.
-CAUTION
When not actively using the oscilloscope,
switch to STORE or VIEW mode, thus
turning off the write gun and eliminating
the possibility of burning the storage mesh.
Whenin WRITE, NORM, or MAX Wmode,
any visible trace may cause permanent
damage to the CRT if display is left for
prolonged periods oftime., Topreventthis
from happening, periodically erase the dis-
play or switch to STORE mode if you wish
to retain the image.
b. For variable persistence operation, press the
WRITE push button. Use minimum INTENSITY and
maximum PERSISTENCE compatible with display.
с. Use MAXWRITE mode only for fast sweep time,
single shot display, or to improve the uniformity of
trace intensity. The MAX W. mode causes more rapid
positive fading onthe CRT and persistence or storage
time of the display is thus reduced.
dd. Tostore a display, press the WRITE push but-
ton, adiustthe INTENSITY and PERSISTENCE for the
desired display, and press the STORE push button.
e, Toviewastoreddisplay, press the VIEW push
button.
f. Tostore more than one display, press the WRITE
push button, set PERSISTENCE fully clockwise and
INTENSITY as required; allow first display to be writ-
tenontheCRT, Set INTENSITY fullycounterclockwise
andconnect the second signaitobe stored. Reset ver-
tical POSITION if second display is not to be super-
imposed onfirst. Slowlyrotate INTENSITY clockwise
until second display appears, Press the STORE push
button.
g. A display which is stored when the Model 181
A/AR power is turned off will remain stored for sev-
eral days. 'To redisplay the stored waveform, press
the STORE pushbutton, turn POSITION controls fully
cew before turning power on, Apply power to Model
181A/AR and allow 5 minute warm-up. If stored sig-
026124
Section HT
Paragraphs 3-44 to 3-47
nal was written in WRITE mode, depress WRITE
pushbutton, Iistored in MAX W mode, depress MAX
W pushbutton. Depress VIEW pushbutton to cbserve
waveform. |
h, Toeraseallpersistent or stored displays, set
mode to WRITE ( or Max Write Jand then the ERASE
push button for approximately 2 seconds, thenrelease.
i. If only a portion of a slow sweep display is de-
sired, press the STORE push button when the trace
has beenwrittentothe desired point; the write gun is
blanked and the written portion is stored.
i. Use a viewing hood, if desired, to improve
screen-display contrast.
3-44. SINGLE-SHOT OPERATION.
3-45. To write or store single-shot phenomena, a trial
setting of INTENSITY is the best approach. The amp-
litude of the phenomena and the sweep-iime required
to display it will affect the persistence. For example,
with maximum PERSISTENCE and some settings of
INTENSITY, a single-shot straight-line may bloom.
A single-shot signal with amplitude variations may not
cause bloom. To determine the best INTENSITY. set-
ting, connect a signal which approximates the sweep
time and amplitude of the single-shot signalto be writ-
ten. Set PERSISTENCE fully clockwise and trigger a
single sweep of the test signal. Set the INTENSITY
as far as possible without causing blooming. Repeat
this procedure, varying the INTENSITY, until the proper
display is obtained. This setup should give maximum
persistence to the single-shot display. After the sig-
nai has been written, press the STORE push button to
retain the display.
3-46. Single-shot signals which require a sweep time
faster than 20 microseconds per division can be writ-
ten with more brightness by switching tothe Max Write
mode, The screen will be unevenly illuminated after
erasing when in Max Write, Figure 3-2B; however, IN-
TENSITY canbe set high enough to make the display vis-
ible throughthe illumination. A display writtenin Max
Write will be more rapidly obscured by positive fading
than a signal written in NORMAL.
3-47, Single~shot signals which require a sweep time
between 200 and 20 microseconds per division may
have low brightness at the center of the screen. Fire
a single-shot test signal with INTENSITY and PERSIST -
ENCE fully clockwise and press the WRITE push but-
ton. HH center screen brightness is low, wait for one
to three minutes for the low brightness area to become
brighter. Likewise, if the entire display brighiness
appears below a usable level, or the display is not
visible at all, wait for one tofive minutes for the dis~
play to appear.
3-5
Model 181A/AR -
Section IV
Paragraphs 4-1 to 4-11
SECTION IV
PRINCIPLES OF OPERATION
4-1. INTRODUCTION.
4-2, This section provides circuit theory analysis of
the Model 181A/AR Oscilloscope. Since variable per-
sistence and storage techniques may be somewhat un-
familiar to the reader, basic theory of operation wili
be explained first to aid in grasping these concepts,
An over-all block diagram is explained next, followed
by a detailed description of the individual circuits.
4-3. VAR PERSISTENCE & STORAGE.
4-4. STORAGE PRINCIPLES.
4-5. TheModel 181A/AR Storage CRT consists mainly
of a conventional electron gun with deflection plates
(write gun), an aluminized phosphor viewing screen,
a pair of flood guns operated in parallel, flood beam
shaping and accelerating grids, afloodbeam collima-
tor, a collector mesh, and a storage mesh as shown
in Figure 4-1.
4-6, The write gun functions as a conventional elec-
trostatic deflection gun, delivering high velocity elec-
trons to selected poinis on the phosphor viewing screen.
The elements which provide storage and variable per-
sistence are located betweenthe write gun andthe phos
phor,
4-7. The flood guns are physically located just out-
gide the horizontal deflection plates. A cloud of elec-
trons is emitfed by each flood gun cathode. These
clouds are combined, shaped, and accelerated by two
control grids. It shouldbe notedthat under certaincon-
ditions the twoelectronclouds will appear as lightareas
onthe viewing screen when the instrument is first turned
on. The combinedcloud is further shapedandacceler-
ated by the collimator { a coating on the inside of the
funnel section of the glass). The positive voltage on
the collimator is adiusted so that the flood-gun elec-
tron cioud just fills the CRT viewing screen. The
cloud is further accelerated toward the storage mesh
and viewing screen-by the collector mesh. After pas-
sing through the collector mesh, the flood electrons
are further controlled by potentials on the storage
mesh and surface. В
POST
ACCELERATOR
FLOOD 7 НН
y mip rm
4 PHOSPHOR
VIEWING
7 SCREEN
Zas
WRITE GUN”.
AQUADAG 4 7
COLLIMATOR ETORAGE
COLLECTOR SURFACE
MESH 14 НАНТ
“à po nage
|
|
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f
1
A
Figure 4-1, Simplified CRT Construction.
02612-2
4-8. The storage mesh is iccated between the collector
mesh and the phosphor, The back side of this meshis
coated with a layer of non-conductive material. The
storage of information takes place on the surface of
this non-conductive material (storage surface),
4-9, The basis for storage of information onthe non-
conductive material is the secondary emission ratio
curve shown in Figure 4-2, This curve shows the ratio
of the number of electrons leaving the surface to the
energy of the electrons striking the surface. At an
energy of about 40 electron/volts (ev) the number of
elecirons leaving the surface is equal to the number
arriving. The point where the secondary emission
ratio is equal to unity is called "first crossover. " If
the surface is bombardedwithelectrons with more than
40 ev of energy, the surface potential rises because
more electrons are leaving thanarriving. If the sur-
face is bombarded with electrons with less than 40ev
of energy, the surface potential decreases because
fewer electrons are leaving than arriving.
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Figure 4-2. Secondary Emission Ratio.
4-10. When the ERASE push button is pressed, the
storage mesh is changed to the same potential as the
collector mesh {+156v). The storage surface is also
changed to nearly this same potential by capacitive
coupling. Since the surface is then being bombarded
by electrons with energies muchhigher thanfirst cross-
over energy, the entire storage potential becomes
equal to +156 volts. The surface potential cannot in-
crease beyond +1566 volts because the collector mesh
would then repel the emitted electrons back to the
storage surface, tending to decrease the surface po-
tential. |
4-11, When the ERASE push button is released, (see
Figure 4-3) the storage mesh is now changed to +3. 3
volts and the storage surface follows to ihe same po-
tential by capacitive coupling. The surface potential
4-1
DN
ni
Section IV |
Paragraphs 4-12 to 4-16
then decavs to zero volts by action of the flood gun
electrons (surface below first crossover, brought to
flood gun cathode potential). After 100 milliseconds,
the storage mesh ig raised to +13. 3 volts and heid
there for 200 milliseconds. The storage suríace fol-
lows to +10 volts by capacitive coupling, buf immedi-
ately starts decaying toward zero volts by capturing
flood gun electrons. Atthe end of the 200 milliseconds,
the storage mesh is brought back to +3. 3 volts, The
storage surface is consequently reduced from zero
volts to ~10 volis by capacitive coupling.
4-12. Since the write gun electrons reach the storage
surface withenergy much higher than first crossover
energy, they charge the surface in a positive direc-
tionwherever they strike. This charge pattern on the
storage surface remains for a considerable length of
time since the storage material is a very good insula-
tor.
4-13. Those areas of the storage surface which are
charged to near zero volts allow the field created by
the high positive potential on the post accelerator to
"reach through" and capture flood gun electrons, ac-
celerating them to strike the phosphor viewing screen,
thereby causing the phosphor to emit light. Thusthe
pattern of charge on the storage surface is made vis-
ible,
- 4-14, The secondary electrons emitted by the storage
surface where the write gun electrons strike must
charge the surface from its erased potential to about
«D volts before floodelectirons can be captured by the
Model 181A/AR
post accelerator. Thus the writing speed of the CRT
could be enhanced by erasing the surface to just below
this "cutoff" level. This is what the MAX WRITE mode
does. The disadvantages of operating inthis mode are
reduced storage time and reducedcontrast ratio. The
"cutoff" potentials of variousareas of the storage sur-
face may not be exactly the same. Thus, the back~
ground illumination may not be uniform when the storage
surface is erased in the MAX WRITE mode.
4-15. VARIABLE PERSISTENCE.
4-16, Figure 4-4 represents the method of obtaining
variable persistence. The unwritten storage surface
after erasure is at approximately -10 volts. Those
areas of the storage surface which are struck by elec-
trons from the write gun become charged to near zero
volts. A +10 volt puise applied to the storage mesh
moves the unwriften areas of the storage surface to
near zero volisandthe writtenareastonear +i0 volts.
While at this potential, the written areas of the stor-
age surface attract and capture flood gun electrons,
whichtends to lower the potential of these areas, When
the storage mesh returnstoits normal level, the stor-
age surface drops 10 volts, The unwritten areas of
the storage surface return to a -10 volt potentialand
the written areas return to a slightly negative poten-
tial, somewhat lower (more negative) than their ini-
tial value. This decrease in potential reduces the
ability of the post accelerator potential fo reach through
and capture flood electrons, thus reducing the trace
brightness slightly.
ый
e100 MSEC——e——_—200 MSEC———
RELEASE
ERASE
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STORAGE MESH
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STORAGE SURFACE
/ POTENTIAL
ee eo ko
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Figure 4-3. Storage Mesh and Surface Potentials During Erasure.
4-2
02612~1
Model 181A/AR
Section IV
Paragraphs 4-17 to 4-30
STORAGE MESH
POTENTIAL
pe ОГ ОГ
a SURFACE
POTENTIAL
8A
Figure 4-4. Variable Persistence Accomplishment Through Pulsed Erasure.
4-17. 1f this procedure is repeated many times, the
stored trace will eventually be erased. The time re-
quired to accomplish this erasure is controlled by
varying the duty cycle of the pulses applied to the stor-
age mesh (or by varying the pulse width if the pulse
repetition rate remains fixed).
4-18, During the time the storage mesh is pulsed pos-
itive, floodelectronsare allowed through to the phos-
phor viewing screen. Thusa light background glow is
visible when the CRT is used in the variable persis-
tence mode.
A-19.. NORMAL.
4-20. 1! the storage mesh potential is reduced to -25
volts it acts as a control grid to fiood gun electrons
and prevents them from reaching the phosphor. How-
ever, it hag little affect on write gun electrons, ailow-
ing many of them to reach the phosphor viewing screen,
Some of the write gun electrons strike the storage sur-
face, charging it positive toward zero volts wherever
they strike, Thusthe CRT appearstoact as a conven-
tional CRT without variable persistence or storage.
However, when the storage mesh is brought back to
+3. 3 volts, those areas of the storage surface which
have been struck by write gun electrons allow flood
electrons to be captured by the post accelerator field,
and thus display the pattern that was written on the
phosphor while the storage mesh was at -25 volts,
4-21. In order to view a stored trace for one minute
or more, the storage mesh is held at a constant +3.3
volts. This may be accomplished by reducing the
width of the variable persistence erase pulses to zero
(corresponding to maximum persistence), or by actu-
ally disconnecting the pulses from the storage mesh,
The write gun may be turned off if desired, to prevent
additional writing on the storage surface,
4-22. The mechanism which limits viewing time is
the "fade positive" of the storage surface ( entire
screen illuminated). This is caused by positive ions
reaching the storage surface and charging it positive,
The positive ions are generated by flood gun electrons
striking residual gag molecules in the CRT. To ob-
tain an extended storage time, the flood guns should
026122
be turned off. This is done in the STORE mode; how-
ever, thefloodgunsare turned on eccasionally to per-
mit viewing of the stored trace at à reduced intensity.
â-23. OVER-ALL DESCRIPTION.
4-24. GENERAL.
4-25. The Model 181A/AR Oscilloscope consists of a
low-voltage power supply, a calibrator, four external
output isolation amplifiers, a high voltage power sup-
ply, a gate amplifier, a horizontal amplifier, and
storage and variable persistence puise circuitry. Fig-
ure 4-5 shows the functional relationship oí these cir»
cuits. The instrument may be operated as a general
purpose, a variable persistence, or a storage oscii-
loscope. Circuit operation in all three modes is des-
scribed in this section.
4-26. Three input signals--intensity, horizontal de-
flection, and vertical deflection--are necessary to
obtain a usable display on the CRT. The circuitry for
the intensity and horizontal deflection signals is ex-
plained in the following paragraphs which are refer-
enced to Figure 4-5. The vertical deflection signal
is coupled to the CRT from the Vertical Plug-In.
4-27, INTERNAL.
4-28. Horizontal deflection signals may be obtained
from the Horizontal Plug-In by positioning the HORI-
ZONTAL DISPLAY switch to INT. Thisapplies - 100
volts tothe plug-in which produces an unblanking gate
and generates an internal sweep signal.
4-29. The unblanking gate is coupled from the Hori-
zontal Plug-Intothe gate amplifier where it ig summed
with the Z-Axis Input, chopped blanking signals, and
the unbianking signal from the storage pulse circuit.
The resulting signal is amplified, coupled through the
high voltage power supply, and applied to the CRT
write gun grid to control the display intensity.
4-30. Each unblanking gate. signal developed by the
gate amplifier also generates analternate trigger sig-
nai. 'This alternate trigger is directiy coupled to the
Vertical Plug-In. (The Operating and Service Manual
for the Vertical Plug-In unit employed should be re-
ferred to for the signal function. )
4-3
Section IV
Model 181A/AR
Figure 4-5
| НО EXT]
ExT у TC HORIZONTAL |
AINPUT| 7 ; PRE-AMP |
- [POSITION]
О
| O MAGNIFIER
|
—
HORIZONTAL E HORIZONTAL
7 INTERNAL AMPLIFIER DEFLECTION
SWEEP |
}
|
| | | |
INTERNAL L(y [FIND BEAM dl
DISPLAY ; is 4 KV
HORIZONTAL ; .
PLUG = IN
© [INTENSITY VERTICAL
} DEFLECTION
|
|
|
| |
UNBLANKING A
ALTE RNAT - | HIGH
NO GATE VERTICAL / «— ALTERNAIE | GATE VOLTAGE
my PLUG-IN Y wes CHOPPED ——e AMPLIFIER POWER
¡E-AXISIN BLANKING SUPPLY :
LINPUTIZ a +7KY
ii TO POST
| ACCEL
:
( [Focus]
ERASE | O
UNBLANKING [ERASE]
GATE
+56 — mm}
EU
tov : PULSER ERASE
IK HZ CALIBRATOR CIRCUIT
|
| |
SIGNALS MAX WRITE О О +23V UNREG
FROM REAR WRITE. PERSISTENCE LOW 8 + 156V
HORIZONTAL, < ie > PANEL A | +00 Y
PLUG-IN SIGNALS | AL. | POWER В + 5V
— VIEW 3 - 12.6 Y
STORE 00V
BlA—L—i
Figure 4-5. Overali Block Diagram
4.4 02612-2
Model 181A/AR
4-31. The internal sweep from the Horizontal Plug-
In is coupled through the HORIZONTAL DISPLAY
switch to the horizontal output amplifier. Here it is
— converted to a differential signal, amplified, and ap-~
ВЕ plied to the CRT horizontal deflection plates.
4-32. EXTERNAL.
4-33. Positioning the HORIZONTAL DISPLAY switch
to EXT removes the internal display voltage from the
Horizontal Plug-In. The unblanking gate and the in-
ternal sweep are therefore not generated by the plug-in.
4-34, Gate amplifier operation (and thus CRT intens-
ification) is determined by: an externally applied Z-
Axis Input signal, the chopped blanking signal from
the Vertical Plug-In, and an unblanking signal from
the storage pulse circuit. When in EXT, the gate amp- .
lifier will produce an alternate trigger only if the ex-
ternal input signal is similar to the normal unblanking
gate.
4-35. The externally applied horizontal deflection sig-
nal is preamplified, coupled to the output amplifier,
converted to a differential output, and applied to the
CRT horizontal deflection plates.
4-36. CIRCUIT DESCRIPTION.
4-37. The following paragraphs area detailed descrip-
tion of the circuits and {heir functions in the Model 181
A/AR Oscilloscope.
4-38. LOW VOLTAGE POWER SUPPLY (LVPS).
4-39, The low voltage power supply produces six de
voltages plus the CRT write and {flood gun filament
power. The -100, -12.6, +15, +100, and +156 volt
supplies are regulated and used throughout the Model
181A/AR and the plug-in units. An unregulated +23v
is produced for use by the High Voltage Power Supply
(HVPS) and the pilot lamp. A regulated +105v is also
produced for use only within the LVPS,
4-40, Figure 4-6 illustrates a basic regulated power
supply. The series regulator and the parallel combi-
nation of the loadandthe sensing device divide the еп-
tire applied voltage. Iftheloadchanges, thus changing
the voltage drop across the load, the sensing device
will detect it and cause the resistance of the series
regulator to change in the required manner to restore
the output to the desired voltage level.
4-41, Refer to the schematic diagram of the LVPS,
Figure 8-21. Theclosing of 85 supplies power to the
primary of T1, The dual primary windings of TI may
be connected in series for 230v operation or in para-
Île! for 115v operation. S56, located on the rear panel
of the instrument, switches these windings for 115vor
230v operation.
4-42. The àc voltages developed by the secondary wind-
ings of T1 are bridge rectified, filtered, fused and
applied to the regulating circuits. Decoupling RC and
LC filter networks are employed for circuit isolation
where required.
02612-2
Section IV
Paragraphs 4-31 to 4-48
4-43. The -100v output is used as a reference for the
other regulating circuits. It must be adjusted first
since its output will affect all other regulated LY PS
outputs.
4-44, -100 VOLT SUPPLY, A portion of the de volt-
_ age from the -100v rectifier-filter circuit is dropped
across ATR5 and series regulator Q4. The remainder
is dropped across the voltage divider network A8R35,
ASR36, and A8R37. If the -100v supply were to de-
crease in amplitude, a small portion of the positive-
going change would be felt on the base of A8Q12. This
change would be coupled through A8V2 and A8Q11 to
the emitter of A8Q12. The difference between the in-
puts to A8Q12, a positive-going signal, is coupled
through current amplifier, A8Q10, tothe base of series
regulator, Q4. Less voltage is dropped by Q4, and
the -100v supply increases tonormal. ASC8and ASR29
prevent high frequency oscillation of the series regu-
lator. ABCRS8 and ASCR9 protect ASQ11 and A8Q12
respectively from reverse voltage breakdown in case
the output voltage is shorted. ABCRI10 acts to prevent
reverse charging of A8C10 in the event F6 opens.
A8CR12 protects A8Q10 and ABQ4 from reverse volt-
age breakdown during instrument turn-on.
4-45, +100 VOLT SUPPLY. Operation of the +100v
supply is similar to the -100v supply except that the
base of A8Q2 is held at a constant voltage by A8Vi.
Any variations in the output are felt only on the base
of A8Q3 and inverted prior to coupling through A8Q1
to the series regulator Q1. |
4-46, +105 VOLT SUPPLY, Afilteredde voltage from
ATCR1-4and A7C1is applied across A7R2, ABRÍ and
breakdown diode ABVRIL., Zener action keeps the top
of ASVE! five volts more positive than the bottom,
which is at +100v. The +105v from A8VYR! isusedto -
provide bias current for A8Q1 and A8Q3.
4-47. +156 VOLT SUPPLY. The rectifiedandfiltered
voltage from A7CR1-4 and A7C1 is applied across
A7Riandbreakdown diode AVVRI. - Zeneraction Keeps
the top of A7VRI1 356. 2 volts more positive than the bot-
tom, which is at +100v. The 156 voll potential at
ATVR! is applied to the CRT collector mesh, and is
also used for the ERASE function.
4-48. -12.6 VOLT SUPPLY. The voltage from the
-12. Gv rectifier filter is dropped across the series
regulator Q3, A8R22, and the load. Any variation in
output is coupled through voliage amplifier ABQY and
current amplifier ASQT to the base of the series regu-
lator Q3. A8C6 and ASR20 prevent high frequency
oscillation of the regulator.
SERIES | | _ o
REGULATOR | : |
Е SENSING ХОА
К DEVICE “OUT 7
1 |
| |
é Lu)
BOA SAR AG
Figure 4-6. Basic Regulated Power Supply.
4-5
Menus”
Section IV
~ Paragraphs 4-49 to 4-58
4-49, The current limiter, ABQ8, and ABR22 provide
protection for the series regulator, Q3. Ii the output
becomes shorted, the voltage drop across ABR22 {urns
on ABQ8. The negative signal from the collector of
ABQ8 is coupledthrough the driver ABQT to the series
regulator Q3, tending to turn it off. Output current
is thus limitedto only that required to keep ABQE con-
ducting.
4-50. +15 VOLT SUPPLY, The+15 voit supply is sim-
ilar to the -12.0v supply except that changes in the
output are applied tothe base of A8Q5 and inverted be-
fore being coupled through ABQ4 tothe series regula-
tor, A8Q2.
4-51. PLUG.IN POWER.
4-52. Table 4-1 lists the current available from each
power supply for use by the vertical and horizontal
plug-ins. Users desiring to design special purpose
circuits should not exceed the capabilities shown in
the table. There isno minimum current requirement
for any supply.
Table 4-1. LVPS Current Capabilities
Maximum Safe -
Current Available
Power Supply
+100 VDC 160 ma
+15 VDC | 428 ma
"12.5 VDC 125 ma
-100 VDC ‘80 ma
4.53. CALIBRATOR.
4-54. The calibrator circuit performs a dual function--
it provides a 1kHz output signal of 10v pk-pk, +1% for
calibration purposes, and a lkHz, -100v signal for
the storage puise circuit (see Figure 8-15}, A1Q6 and
AÎQ/ areusedina free-running multivibraior circuit.
Diodes AICR12 and AICR14 provide voltage protection
to the transistors. The collector of AIQŸ is discon-
Model 181A/AR.
nectedfrom A1C15 by AJCR13 as A1Q7 turns off, pro-
viding a faster puise rise-time. A1L3 and AIC16 isolate
the multivibrator from the -100v supply, while A1R31
and A1C17 isolate it from the +15v supply. The 10v
square wave output is applied to a front-panel connec-
tor foruse inprobe compensation and sensitivity cali-
“bration, and the -100v sguare wave output from the
collector of A1Q6 is applied to the pulse circuit.
4-55. QUTPUT ISOLATION AMPLIFIERS.
4-56, Signals derivedfrom the Horizontal Plug-In are
coupled to rear panel BNC connectors J5-8 (refer to
Figure 8-7). Four emitter followers, A2Q1-4, are
employed as isolation amplifiers. The signals actu-
ally developedare determined by the Horizontal Plug-
Inusedinthe instrument; hence, the signals available
can be determined by referring to the Operating and -
Service Manual for the applicable plug-in.
4-57. HIGH VOLTAGE POWER SUPPLY [HVPS).
4-58. Three regulated voltages are produced by the
HV PS: -1440v, +7kv, anda control grid voltage of
-1450v to-1500v (refer to Figure 4-7). A regulated
oscillator isusedto develop the required high voltages
in transformer A5T1. The -1440v supply is sampled
to provide control of the osc illator output and thus reg-
ulate all three voltages.
4-59. Unregulated +23v from the LVPS provides pri-
mary power to oscillator Q5 operatingat approximately
35kHz {see Figure 8-18). The outputs from the high
voltage transformer AbT1are coupledtotwo-haif wave
rectifier/filter circuits and to a voltage tripler/filter
circuit. CRT control grid voltage is rectified by
ASCR1 and filtered. The write gun cathode voltage
is rectified by ASCR2 while ASR2 establishes the de
potential applied to its control grid. Voltage regula-
tors, Al1YÍ and AIV2, limit the maximum potential
difference between the control grid and the cathode to
140v. The CRT focus voltage is obtained {rom the
~1440 cathode voltage by a voltage divider network of *
which R5, the FOCUS control, is a part. Resistor,
HV :
OSCILLATOR +
SSKHZ - ' ;
+100V
REGULATOR | {
HV ADJUST
VOLTAGE
TRIPLER + 7KY
RECTIFIER
p
& FILTER ACCÈL
RECTIFIER - =-1470Y
& FILTER
RECTIFIER - 10
& FILTER
Se
2
ma ¡FOCUS
| Ae Bi
Figure 4-7. HVPS Block Diagram.
4-6
02612-1
Model 181A/AR
Section TV.
Paragraphs 4-60 to 4-67
UNBLANKING GATE
CHOPPED BLANKING
Z-AXIS INPUT
PULSE INPUT
OV — AMPLIFIER
A Г
о HORIZONTAL ~ 6r/0 si . Tuy o UNBLADKING
CONTO DISPLAY LT >“ | В
DISPLAY — Ou DIFFERENTIATOR
{-iCOv) INT |
Al, Q5 ALTERNATE
| ” TRIGGER
VERT y
BEAM FINDER € NC | |
FIND BEAM] - | lo
| | “ | TX
-2.6V — ‘ / |
INTENSITY o
i¡BIA—B-34
Figure 4-8, Gate Amplifier Block Diagram.
R6, maintains the write gun filamentat cathode poten-
tial. The voltage tripler circuit of A9CR1-3andA9C1-4
is contained on Assembiy A9, the output of which (+7
kv) is applied to the CRT post-accelerator anode.
4-60. Changes in output of the -1440vdc supply are de-
tected by the regulator A1Q8-A1Q10 to change the oper-
ating voltage of oscillator Q5. Assume that the -1440
supply voltage decreases {goes positive). À positive-
coing signal is applied through the regulator to the
base of Q5, causing it to conduct for a greater portion
of the input cycle. The oscillation amplitude is there-
fore varied soas to oppose the original change in out-
put voltage. This causes a voltage change to appear
on the primary of A5T1 and increases the voltage of
the secondary. The steady state value of the CRT
cathode voltage is established by A1R38, the High
Voltage Adjust, by setting the normal dc value on the
base of the A1Q8. Inductor A4L1l suppresses any pos-
sible high frequency parasitic oscillation.
4-61. GATE AMPLIFIER.
4-62. The inputs to the gate amplifier {refer to Fig-
ure 4-8) are the unblanking gate, the chopped blanking,
the Z-AXIS INPUT, andthe storage pulse circuit sig-
nals. These four signals may be present either singly
or simultaneously, depending upon control settings.
Theyare summed with a current established by three
front panel controls--FIND BEAM, INTENSITY, and
HORIZONTAL DISPLAY. Depressing FIND BEAM
~ shunts the normally adjustable INTENSITY control.
and supplies maximum current from this source. Set-
ting HORIZONTAL DISPLAY to EXT SENS or EXT
CAL supplies additional current to brighten the beam.
4-63. The gate amplifier, A1Q1-A1Q4, senses the in-
put signal current, converisitto a voltage, amplifies
it, and couples itto the control grid of the CRT write
gun. And in addition, the output signal is also differ-
entiated, clipped, and coupled to the Vertical Plug-
in for use as a trigger signal if desired.
02612-2
4-64. The input currents to the gate amplifier (refer
to Figure 8-7) are summed in the low impedance
emitter circuit of AlQ1, The resulting current is
coupled to the complementary feedback amplifier(a
current fed operational amplifier), A1Q2-A1Q4, where
it is converted to a voltage and coupled to the control
grid of the CRT write gun. The large negative feed-
back from the collectors of A1Q3 and AlQ4 to the base
of A1Q2 provides the complementary feedback ampli-
‘fier with a very stable gain, Trimmer capacitors,
Al1C8 and A1C9, adjust the high frequency feedback.
Diode A1CR6 provides temperature compensation for
A1Q3, while A1CR7 and A1CR8 protect A1Q3 and A1Q4
from voltage breakdown. Diode, AICR10 and ATR57,
isolate A1Q3 and A1Q4 from the high voltage in the con-
trol grid circuit of the CRT write gun in the event of
a grid or cathode short to ground. The output from
AlQ3andAl1Q4 is differentiated by A1C13, AIR22 and
A1R23, and coupled through A1Q5 andthe positive clip-
per, AICR11, to the Vertical Plug-In for alternate
triggering purposes.
4.65. HORIZONTAL AMPLIFIER.
4-66. The block diagram, Figure 4-9, illustrates the
major circuit functions. The horizontal amplifier can
be driven by either an internally derived signal or by
an external signal applied to the HORIZONTAL EXT
INPUT front panel BNC jack. Positioning the HORI-
ZONTAL DISPLAY controlto INT disconnects the ex-
ternal signal input and grounds the horizontal preamp-
lifier input. The Internal Sweep signal is connected
through the HORIZONTAL DISPLAY switch to the hor-
izontal output amplifier.
4-87, The EXT INPUT BNC, J4, is connected to the
input of the preamplifier when either EXT SENS or
EXT CAL is selected; the preamplifier, in turn, is
coupled tothe output amplifier. Selections of EXT SENS
permits varying the amplitude of the preamplifier out-
put by adjustment of the HORIZONTAL DISPLAY con-
4-7
Section IV
Paragraphs 4-68 to 4-75
Model 181A/AR
BISPLAY MAGNIFIER
Qro 5/0 SI
INT CRT
INPUT HORIZONTAL
FROM DEFLECTION
PLATES
JB
“+
R3 HORIZONTAL
EXT | O
INPUT _ POSITION
SIGNAL EXT CAL |
ННА-В-2
| “Figure 4-9,
trol. When EXT CAL is selected, this control, RI,
is shorted; the output amplitude, therefore, is deter-
mined by the amplitude of the input signal.
4-68, The signal selectedis fed into the output ampli-
fier where it is summed with a current established by
the HORIZONTAL POSITION controls. The resuitant
current is converted to a differential signal, ampli-
fied, andappliedto the CRT horizontal deflection plates,
4-69, External input signalsare preamplified by A3QI
-and A3Q2 (refer to Figure 8-10). The high input im-
pedance of A3Q1 minimizes loading of the external in-
put source. Diode A3CRI1 protects A3Q1 from high
level inputs. A3Q2 has a low output impedance suit-
able for driving A3Q3. The BANDWIDTH/ PHASE
Switeh, A3S1, would be positioned in PHASE whenaccu-
rate X- Y measurement is desired, In the PHASE
position, A3C2and A3C3 are switched in, decreasing
the preamplifier bandwidth. The total horizontalamp-
lifier signal delay is therefore made equal to signal
delay in the Vertical Plug-In. The vernier balance,
A3R7, is adjusted so that 0 vdc appears across the
HORIZONTAL DISPLAY control, thus eliminating any
horizontal dc shift as the control is operated.
4-70, Input signals to A3Q3 are summed in the low im-
pedance emitter circuit with a current established by
the setting of the POSITION controls A3R2 and A3R3.
A3Q6 is driven by the low impedance of emitter fol-
lower A3Q4. The input signal to A3Q6 is coupled
through the MAGNIFIER switch, S4, tothecompiemen- -
tary driver A3Q7. S4 provides for selection of incre-
mental gain levels by selecting the amount of emitter
degeneration employed with A3@6and A3Q7. Increas-
ing degeneration decreases gain. Adjustment A3R30
along with A3R31 controls the gain when in the X10
position, ASR32/A3R33 control the X5 gain, and A3R34/
A3R35 determine the X1 horizontal gain, The dc bal-
ance of A3Q6 and A3Q7 is adjusted by A3R37 which
controls the emitter potentials. Transistor A3@5 pro-
vides a low impedance voltage source for the base of
A3Q7. The differential signal at the collectors of A3Q6
and A3Q7 is applied to the complementary feedback
amplifiers (current-fed amplifiers), A3Q8-Q10 and
A3Q11-Q13, convertedtoa voltage, and coupled to the
horizontal deflection plates of the CRT. A3CR3 pre-
vents A3Q6 from saturating, while ABCR6 serves the
same purpose for A3Q7. Diodes A3CR3/CR4 and
4-8
‚wave signal,
Horizontal Amplifier Block Diagram.
ASCR7/CR8 limit the amplifier output to the CRT de- .
flection plates to within +6vand +94v regardless oi the
amplitude of the input signal.
4-71, Depressing FIND BEAM switch 53 disables lim-
iter ASCR7/CRB andbliocks the input signal to A3QIT.
The differential gain is effectively reduced by half and
the electron beam is confined to the horizontal limits
of the CRT screen.
4-72, The gain of the complementary feedback ampli-
fier is made very stable by coupling a generous amount
of negative feedback from the collectors of A3Q9/Q10
to the base of A3Q8, andfrom the collectors of A3Q12/
Q13 to the base of A3Q11, The high frequency feed-
back of each amplifier is adjusted by A3C6 or A3C19
individually, while A3C9 adjusts the feedback for both.
Diodes A3CR5 and A3CR9 provide temperature comnen-
sation for A3Q10 and A3Q13.
4.73. PULSE CIRCUIT.
4-74, Pulses of adjustable level and width are used to
controlthe variable persistence and storage capability
of the Model 181A/AR Oscilloscope. They are ap-
plied to the CRT storage mesh when operating in the
WRITE and MAX WRITE modes, applied to the flood
gun accelerator in the STORE mode, and used to key
the gate amplifier for CRT unblanking.
4-75, VARIABLE PERSISTENCE. The multivibrator
circuit, (Figure 8-17), isthe source of a 1 kHz square
This signal, in turn, is applied to the
pulse circuit which modifies the width and level of the
puise. À -100v square wave is obtainedfrom the junc-
tion of A1C14 and AÎR28 and fed to the base of A6Q3
through A6R8. Inverted and level-shifted by A6Q3,
the resultant +15v square wave at the collector of A6Q3
is applied through A6CR2 and differentiated byA6R13/
ABC2. Applied to the base of A6Q4 through AGCR3,
the amplitude of the pulse at the anode of ABCR3 is
established by the ratio of A6R12 andthe PERSISTENCE
control setting, RY. Asaresult of the charging time
constant of A6C2/A6R13, the variable amplitude sig-
nalisfeltas a variation in width (i. e. duration) at the
base of A6Q4. By varyingthe conduction time of A6Q4,
the time required to erase atrace has been controlled.
In other words, varying the erase time is essentially
the same as varying the display time, and this, in
turn, is known as variable persistence.
02612-2
Model 181A/AR
4-76. NORMAL, Selection of this mode permits the
Model 181A/AR to be employedas a conventional oscil-
loscope. With NORMAL activated, the junction of
AGR16/A6R19 is grounded and the storage mesh falls
to -25v. Because of this negative potential, the vari-
able persistence and storage capabilities are therefore
disabled.
4-77. WRITE and MAX WRITE. Operating in these
modes allows normal viewing of the display and pre-
pares it for storing, MAX WRITE is used only when
necessary, suchas inviewing fast single-shot signals.
4-78, To obtain display uniformity in the MAX WRITE
mode, the CRT collimator voltage should be readjusted
in this mode. Todo so, a multivibrator consisting of
А6016 and A6Q17 is used.
4-79. Whenthe MAX W. pushbutton is depressed, one
side of the multivibrator conducts. Current flow
through A6R47 and A6R46 holds A6Q16 on and A6Q17
off. Thus, the MAX WRITE ADJ pot A6R17 is para-
lileled with WRITE ADJ. Atthe same time, A6R3 is
disabled and MAX WRITE COLLIMA TION ADJ (A6R29)
is enabled. The multivibrator is necessary so that
proper collimation voltage is retained when the VIEW
or STORE mode is selected.
4-80, The setting of the WRITE adjust, A6RI18, adjusts
the positive pulse level at the collector of A6Q4 when
operating in the WRITE mode, while A6R18 in parallel
withthe MAX WRITE adjust, A6GR17, adjusts the level
in the MAX WRITE mode. Pulse level control of the
1 kHz pulses tothe storage meshaffords depth of eras-
ure control which directly affects writing rate, In
other words, the more negative the storage surface
becomes, the longer it will {ake it tobuilduptoa level
high enough to store a trace (refer to Figure 4-4).
4-81, STORE, When the STORE function is selected,
the base of ABQI is grounded, turning it off. This
allows the current flow through A6R2 and A6CRI to
turn ABQ2 on. Meanwhile, the +15v square wave sig-
nalat the collector of A6Q3 is differentiated by A6C1/
ASR2 and applied to the base of A6Q2 through A6CRI.
Thus A6Q2 has a negative voltage developed at its base
during the charging time of A6C1 which turns it off.
The time constant of ABC1/ABR2 is such that A6Q2 is
off for about 50 microseconds each millisecond, and
only during this short interval will a positive poten-
tial be applied to the flood gun accelerator grid,
4-82, While A6Q2 is on, the flood gun accelerator
voltage is established by voltage divider network,
A6R5/A6R6, at -9v. With ABQ2 switched off by the
differentiated 1 kHz pulse, the accelerator voitage is
+43v set by the divider network A6R4, and AGRE.
4-83. With the accelerator grid held at -9v, the fiood
gun electrons are repelled. Thus, when in the STORE
mode, the flood guns are always on, but electronsare
attracted to the storage mesh only when the acceler-
ator grid is at a positive potential, about 5% of the
time. This reduces the display brightness and pro-
vides for greatly increased storage time.
4-84. VIEW. Depressingthe VIEW push button allows
viewing a previously stored display at a brighiness
level determined by the intensity and persistence set-
tings during the writing process. At least one minute
02612-2
Section IV
Paragraphs 4-76 to 4-89
of aggregate viewing is available without trace degrad-
ation.
4-85. When in VIEW, NORMAL, WRITE or MAX
WRITE mode of operation, A6Q1 is turned on by the
current flow through A6R1{o its base. This effectively
grounds the base of A6Q2, holding it off and keeping
the flood gun accelerator potential at +43v.
4-86. The flood gun grid levelissetto provide an op-
— timum flood gun electron distribution at the storage
mesh. This is adjustable and is determined by the
setting of ABR42, whichis in series with ABR7 and the
-100v supply. Stray ac signals on the flood gun grid
lead are decoupled from the flood gun by A6C4.
4-87. ERASE, The push button operating mode selec -
tor switch does not permit energizing the erase cir-
cuitry unless the WRITE or MAX WRITE mode of
operating has been selected. Activation of the ERASE
switch S7 (refer to Figure 8-12) in either ofthese modes -
applies +156v tothe CRT storage meshandto the junc-
tion of A6R36 and AGCRS, The diode AGCRS6 prevents
application of this +156v to the collector of A6Q4 during
ERASE, while ABCR4 prevents the collector from ris-
ing above +15v because of the +100v applied through
‘the voltage divider formed by A6R15, A6CR5, A6R16
and A6R19. Normally nonconducting, A6Q13 is turned
on by application of the +156v which in turn shuts off
A60Qi2. This permits A6C6 to charge positive through
A6R33 and A6R87 to about +4.7v. Theresultant cur-
rentthrough A6R37 causes A6Q14 toconduct and A6QI5
to cease conduction. Currentfiowingthrough ASR43,
AICR15, AIR10 and into the emitter of A1QI causes
the Gate Amplifier to operate so as to blank the CRT
write gun. A clean erasure of the storage mesh is
thereby assured since nowriting of an input signal can
take place during erasure,
4-88. Releasingthe ERASE switch removes the +156v
from the CRT storage meshand from A6R36. Current
no longer flows throughthe base of A6Q13 and conduc-
tionceases. This permits A6Q12 to conduct due to the
current flowthrough ASR34 into its base. The result-
ing 4. Tv negative step atthe collector of A6Q12 is dif-
ferentiated by A6C6/A6R32 and applied to the base of
A6Q11, causing it to cease ‘conduction. Ás a result
of the charging time constant of A6R32 and A6C6, A6Q11
will remain in a nonconducting state for approximately
100 milliseconds. During this time, AGCS is being
charged to +4.7v through A6R31, A6R38, and ABR2Y.
Current flow through A6R38 and AOCRT causes the
Blanking Control Amplifier A6Q14/A6Q15 and the Gate
Amplifier to operate and blank the CRT write gun.
4-89. Control of the voltage applied to the CRT colli-
mator is desired during storage mesh erasure. A por-
tion of the current through A6R31 also flows through
ASR27, placing A6Q8 in a conducting state, and caus-
ing ABQY tocease conduction. The voltage on the base
of A6Q10, therefore, rises to nearly +120v, causing
heavy conduction through A6Q10. This results in its
emitter rising to about +120v due to the voltage drop
across ASR30. Since the collimator is connected to
the emitter of A6Q10, the + 120v developed across
ABR30 is appliedtothe collimator while erasing. This
ensures a more uniform erasure of the storage mesh,
particularly of the periphery of the display area.
4-9
TAR
tepid
Section IV
Paragraphs 4-90 to 4-95
4-90. At the end of the 100 millisecond initial erasing
period, A1Q11 again starts conducting, The result-
ing 4.7v negative step at the collector of A6Q1i is
differentiated by A6R26/A6C5 and applied to the base
of A6QT7, turning it off, A6Q7 will be nonconducting
for approximately 200 milliseconds, while A6Q7 is
off. The current flow through A6R25, AGR39, and
ASQ14 causes the CRT write gun to remain blanked.
Also, the current flow through A6R24 into the base of
A6Q6 drives it into conduction, effectively grounding
the base of A6Q4. With A6Q4 in an off condition for
the 200 millisecond period, the CRT storage mesh
rises to about +13. 3v when operating in the WRITE
mode, and to about +7. 5v in the MAX WRITE mode,
4-91. When the 200 millisecond interval is terminated,
A5Q7 again conducts and turns off A6Q6. This allows
current toflow through A6R13, A6CR3 and the base of
A6Q4, turning it on, and reducing the storage mesh
to the +3. 3v level. Variable-width erase pulses are
again applied to the storage mesh at the 1 kHz rate.
4-92. Ttis desirable to provide for inhibiting the CRT
WRITE functionior a short interval after erasing. The
Model 181A/AR
discharging time constant of A1C6/A1R10 through A1Q1
accomplishes this, and keeps the write gun turned off
momentarily.
4-93, STORAGE PROTECTION, Itispossible to ma-
nipulate the operating mode selector switch so that
. multiple functions or nofunctionatal! may be selected.
This switchis interconnectedto provide several oper-
ational features which protect the stored display {rom
inadvertent erasure of overwrifing. For instance, i
no function is selected, the CRT write gun is blanked
and the PERSISTENCE control is inoperative.
4-94, The write gun blanking is provided by current
flow through A6R22and A6R40 into the base of A6Q14,
thus causing the Gate Amplifier to turnoff the write gun.
4-95, The disabling of the PERSISTENCE conirol is
obtained by utilizing the current flowing through AG6R22
and AGR23 intothe base of AGQ4. This holds A6Q4 in
conductionandkeeps the storage meshat +3, 3v. .Cur-
rentflowing intothe base of A6Q4 prevents the variable
amplitude 1 kHz pulse from turning off A6Q4.
Table 5-1, Required Test Equipment
Recommended Type
Test Equipment Model
Required Characteristics
Voltmeter
Calibrator
hp Model 738AR
or 6920B
i, 2, 10v pk-pk +0. 2%
Test Oscilloscope
hp Model 180A/AR
w/1801A & 1820A
Sensitivity 1v/div
Sweep Speed lu sec
Risetime Зи вес
Sweep output
10:1 Divider Probe
hp Model 10001A +3%
Constant Amplitude
Tektronix Type 190B
50 KHz-50 MHz at
Signal Generator 10v pk-pk
Digital hp Model 3440A +100vde +0, 5%
Voltmeter w/3444A 2.5 ma +2%
100:1 Divider Probe hp Model 11044A 300vde
Square Wave Generator
hp Model 211A/B
200 kHz lv pk-pk
Risetime 30 u sec
Current Source
3,5 ma +. 3%
Oscillator
hp Model 200CD
10 kHz 10v pk-pk
02612-2
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