B+K precision 1403A User manual

v
SMHz
OSCILLOSCOPE
f
{t
K'

IEST INSTRUTUENT
SAFETY \,
WARNIilG
Normal use of test equipment and servieing of test equipmentexposes
you to a eertain
amount of danger from eleetrieal shoek
beeause
testing must often be performed where
exposed
high voltage is present. An eleetrieal shockeausing
10 milliamps of eurrent to pass
through the heart will stop most humanheartbeats. Voltage aslow as35volts de or aerms
shouldbe eonsidered dangerousand hazardoussinee it ean produeea lethal eument under
eertain eonditions. Higher voltage poses
an even greater threat beeause
suehvoltage ean
more easilyproduee a iethal eurrent. Your normal work habitsshould
ineludeall aeeepted
praetiees thCt will prevent eontaet with exposed
high voltage, and that will steer eurrent
away from your nealt in easeof aeeidental eontaet with a high voltage. You will signifi-
eantly redueethe risk faetor if you know andobserve
the following safety preeautions:
1, High voltage up to 1r400
volts is presentwhen
servieingthis oseilloseope. Observe
all
highvoltagepreeautions
whenthe unit is operating
with the ease
removed.
Remember
that a high voltage ehargemay be retained indefinitely, espeeiallyat the CRT soeket
and anode eap. -Discharge high voltage eapaeitors with a groundedtest lead after
removing
power.
2. Dontt expose
high voltage needlessly. Removehousingsand eoversonly whenneees-
sary. Turn off equipment while making test eonneetionsin high-voltage eireuits.
Diseharge
high-voltage eapaeitors
after removingpower.
3. If possible,
familiarize yourself with the equipment
beingtested andthe loeation of its
high voltage points. However, remember that high voltage may appear
at unexpeeted
points in defeetive equipment.
4. Use an insulated floor material or a large, insulated floor mat to stand on, and an
insulated work surfaee on whieh to plaee equipment; and make eertain sueh
surfaees
are not dampor wet.
5. Use the time-proven rfone
handin the poeketnteehniquewhile handlingan instrument
probe. Be partieularly eareful to avoid eontaeting a nearby metal objeet that eould
providea goodground
return path.
6. Whenusingthe oseilloseope,the groundwire of the 3-wire ae power plug pla_ees
the
ehassis
and housingof the oseillos-eope
at earth ground. Do not attempt to defeat the
ground wire eonneetionor float the oseilloseope;
to do so may posea great safety
hazard.
1. Whenusing a probe, toueh only the insulated portion. Never toueh the exposed
tip
portion.
8. Whentesting ae powered equipment,
rememberthat ae line voltage is usually
present
onsome
powerinput eireuits suehasthe on-off switeh, fuses,
powertransformer,ete.
any time the equipment
is eonneeted
to an ae outlet, evenif the equipment
is turned
off. v
eontinued
oninsidebaekeover

v
SERVICE
MANUAL
for
B & K-PRECISION
MODEL
14O3Aand 14O5
SMHz
OSCILLOSCOPE
I}
{lF
K'
tulA€ | luTERm,ATtotuAtcoRP.
6470 W. Contland
St. . Chicago,
lL60635
Telephone
[31
2) 889-1448
usethis address for teehnieal inquiries and replaeement parts orders
WARlrllNG
fhis senrice manual is intended for use by qwlifi.ed electronfcs technfcians
only. To avoid electric shoclg do not perform senlicing urless you are
qnlified to do so.
High voltageof approximately1,400
volts de is present
when
this instru-
ment is operating. AC line voltageis present on the input power eireuits
whenever
the aepower
eordis eonneetedto a live outlet, even
if theseope
is turnedoff. Observeall highvoltage
safety preeautions
when
the housing
is removedfrom the oseilloseope.
Contaeting
exposed
high voltageeould
result in fatal eleetrieshoek.
-

TABLE OF CONTENTS v
Page
TESTINSTRUMENTSAFETY
ooo... o
ro.. r..... o..inside
front
eover
INTRODUCTION
....... r.... or..,
r..
o.ar....
o.oo..
t......1
SPECIFICATIONS..
o........ o....
'.
o.
r.r..... oo..
o..... ...2
CONTROTS
AND
INDICATORS.r... r
o..
r. ooo.ro...... r. or....3
CIRCUIT
DESCRIPTION.................. .... oo.o...
o.o.
...
ti
ADJUSTMENTS..
oI o. o.. o.. o........ rooot. !....... o..... 13
MAINTENANCEo
o. r.
o
o. r
r. o.. r. r.. or
ooor.. oro. t.
o. o..... 1?
TROUBLESHOOIjNG...o....... rr.
r..... o...... .rr....... 20
PARTS IJST. r . . . . . . . . . . r r o . . . I r . . . . o . . o . | . . ] . . . o . t . . . . . 24
VOLTAGE
CHART.... ro... r... rorr.
o.... ro..... o....... .29
CIRCUITBOARD
MAP.
o
r... oo.'. r.
o..
o.o.. oo..... r....... 30
SCHEMATICDIAGRAMo... or........ o.......... t..... o...31
HISTORY
OF
PRODUCTTONCHANGES...
T
ro.o.,....... o.r. o..32
SERVICE
HINTTI
...
o..... r... r
''rr...
rr..
o.......... r.
o..
33
BEFEBBNCE PI'BIICATIONS
Model1403A
InstruetionManual o. . . . . . . . . . . . . . . o
. o . 480-17?-9-001
Modell40SASehematie
Diagram& PartsList. oo....... 499-085-9-001
Model1405
Instruetion
Manual
o.. o... t..... o.o.... . 480-26?-9-001
Model
1405Sehematie
Diagram& PartsList ...o... oo. o 499-164-9-001
Y,
v

vINTRODUClTON
f
SCOPE
OF frIANUAL
This
servieemanual
eovers
B & K-Preeision
Model 1403A from the start of produetion
through
theendof produetion.
It also
eoversModel
1405
from the start of
produetion
until the printing of this serviee
manual. Produetion
ehanges
whiehoeeurafter
the printingof this manual
will be eoveredby
loose
ttAddendumrt
sheets.
The "History of Produetion
Changes"
see-
tion, at the rear of the marrual,
itemizesall
produetion
ehanges
whieh
may
affeet servieing
andrepairof the instruments.
DESCRTPIION
OF EQUTPMENT
TheB & K-Preeision
Model1403A
and
1405
Oseilloseopes are eompaet, single traee,
general purpose instruments for observing
waveforms. These
oseilloseopes
usea 3-ineh
round CRT with a 12 x tZ division
gratieule
whieh overlays
the CRT. Waveforms
eanbe
viewedon about8 x 10
divisions.
Thegratieule
also featues a dB seale, refereneed to six
divisions
amplitude
equals
0 dB.
The vertieal ehannelhasa bandwidth
of de
to 5 M
Hz, and sensitivity of 10 mV/division.
Input impedaneeis 1 Megohm, the standard
value for oseilloseopes. A three-step atten-
uator offers 1:1, 10:1
and 100:1
steps,
plusa
variable gain eontrol offers fully adjustable
waveform amplitude. Terminalsare also
pro-
vided to allow external signals to be applied
direetly to the vertieal defleetion plates of
the CRT.
The horizontalehanneluses
reeurrent
type
sweep,
with four ranges and
a variable eontrol
to spanthe 10
Hz to 100kHz band. The
sweep
ean be synehronized to the waveform being
observed
(internalsyne)with a trigger sensi-
tivity of 1division. External syne is also
available,with a sensitivityof 2 volts
peak-to-
peak.
In X-Y operation, the horizontal ehannel
beeomes
a variable
gainX-axis
amplifier with
maximum
sensitivity
of 300 mV per division.
Bandwidthis up to 250kHz. A Z-axisinput is
provided
for intensity modulation,if desired.
DIFFERENCES BETWEEN ITIODEI.S1403A
AND 1405
Eleetrieally,the Model1403A and1405
are
nearlyidentieal. However,
almost
all external
hardware
and meehanieal
parts are different.
TheModel1405
beeame
a replaeement for the
Model
1403A
in 19?9,
and
featured
adifferent
easeeolor, and many eosmetiediffereneeson
the front panel. All differenees
are itemized
in the rrPartsListn seetion of this serviee
m
anual.
EXCLUSTON
OF mODEL1403
This serviee manual does not eover Model
1403.
Althoughthe Model1403has
a similarity
in funetionto Model1403A,thereareseveral
major differenees
in eireuit designandspeeif-
ieations.
rl7

SPECIFICATIONS Y/
CATHODE BAY TUBE
C3L2P31Bor 75AV831.
VERTICAL AMPIIFTER
Defleetion
Sensitivity:
10mV/div
or better.
Frequeney
Response:
DC: deto 5 MHz(-3 Og).
AC: 2 Hz to 5 MHz(-3dB).
InputImpedanee:
1 MO
shuntedby 35pF max.
Overshoot:
5%or less.
Attenuator:
t, 1-/L0,
1/100multiplierwithin t596.
GainControl Range:
Continuously variable, range greater
than 22dB.
RatedMax,imum
InputVoltage:
300
V (de
+ ae
peak)
or 600
V p-p.
HORIZONTAL AfrTPLIFIER
Defleetion
Sensitivity:
300mV/div
or better.
Frequeney
Response3
DC to 250kHz with EXT. GAIN eontrol
set at maximum. DC to approx.40kHz
with EXT. GAIN eontrol set at mid-
range.
InputImpedanee:
1 M0 (120%) shunted by 30 pF max
(SYNC
switeh
set to INT).
Attenuator
(nXt GAIN):
Continuously
variableto zero.
Rated
Maximum
Input
Voltage:
100
V p-p.
SWEEPCHARACITRISTICS
Sweep
Frequeney:
10 Hz to 100 kHz eontinuously variable
in 4 ranges.
SweepLinearity:
Within
5%.
Synehronization:
Internalor external, negative
slope.
SignalAmplitudeRequiredFor
Synehronization:
Internal: More than 1 div defleetion
oneathoderay tubesereen.
External: Morethan 2 V p-p.
INTENSITY IIIODULAIION
Required
Signalz 25
V p-p.
DIBECT DEFLECTION TERMINATS V
Defleetion
Sensitivity:
10V/div or better.
InputImpedanee:
2.2MQ
shunted
by 25
pFor less.
POWERRBQIIIREMENTS
Ll?
/230 VAC, 50/60 Hz, 16 watts (Unit
deliveredfor useon 117
VAC, 50/60Hz).
DIUENSIONS,OVERALL
Width: 7
-L/2"
(1gO
mm).
Height: 6o
(154
mm),
Depth: IL-27
/32n
(300
mm).
WEIGIIT 8.36lbs
(3.8
kg).
ACCEf|SORIESSUPPLIED
Test Leads.
Spare
Fuse.
InstruetionManual.
Sehematie
Diagram& PartsList. ^.
v

CONTROIS AND INDICATORS
v
BOTTOM
PANEL
2t REAR
PANEL
@ @ @ @rnoruTpANELO)
l8ffE
I sreec,.eer6s1r.y
i*tr?F
l-5'{-r
L,mn,,,J
;''6':
Z axrS rNPut crr9 v otq
-
Fig. 1. Model1405
ControlsAndIndieators.
FRONT PANEL CONTROIS AND
INDICATORS
1. Neon Pilot Lamp. Lights whenseopeis
operating.
2. POWER
Switetu Power
ON-OFFswiteh.
3. EXT SYNC/HOR INPUT Jaek Input for
external syne or external horizontal
signal. Conneet signal eommon to the
adjaeent
ground
terminal.
4. + Jaek Earth andehassis
ground.
VERT INPUT Jaelc Input for vertieal
signal Conneet signal eommonto the
adjaeentground
jaek.
AC-DC Switetr. Seleetor switeh for
vertieal input eoupling. In AC position,
vertieal input is eapaeitively eoupled
and,therefore, de eomponentof signal is
bloeked, permitting observation of ae
eomponentonly. In DC position,
vertieal
input is direetly eoupledand,therefore,
allows both de and ae eomponents of
signal
to eausevertieal defleetion.
5.
It

CONTROI,SI
AND INDICATOBS
7. V ATT Switeh. Vertieal attenuator.
Coarsevertieal amplituderange
seleetor
switeh. Attenuates high amplitude
signalsappliedto VERT INPUT terminal
before eonneetion
to vertieal amplifier,
providing suitable level for waveform
displayon CRT sereen. n1n
(10
mV/div)
position is most sensitive range; signal
applied to vertieal amplifier is unatten-
uated. In 1/10 position, input to vertieal
amplifier is attenuated to l/10 of input
signal level 1/100 position attenuates
vertieal amplifier input to 1/100of input
value. V GAIN eontrol provides fine
adjustment within eaeh range. In GND
position, VERT INPUT jaek is diseon-
neeted from vertieal amplifier and input
of amplifier is grounded. This provides
traee at 0 volts referenee for de eoupled
input, and is eorreet position for making
debalaneeadjustments.
Signal Voltage
To Be ileasrned
(ranges
overlap)
Ventieal
Attenuator
Pcition
Below
0.8Vp-p
(0.3
Vrms)
0.2
to 8Vp-p
(0.0?
to 3Vrms)
Above2Vp-p(0.?Vrms)
1
LlLO
1/100
V GAIN Cmtrol Vertieal gain control.
Fine adjustment
of waveform amplitude.
This eontrol must be fully eloekwisefor
maximum sensitivity; e.g. 10mV/div in
ftlffrangeof V ATTenuator.
t POSITION Control Vertieal position
eontrol Moves
entire waveform up and
down
on CRT sereen.
{> POSffiON Control Horizontal
positioneontrol Moves
entire waveform
left or right on CRT sereen.
SWEBPRANGE Control Coarse sweep
frequeney
seleetorswiteh. The 10-100,
100-1k,
1k-10k, and10k-100k positions
represent
the range of sweepfrequeneies
that are possible with the fine sweep
frequeney eontrol (SWEEP VARI/EXT
GAIN eontrol) within eaeh range. EXT
position seleets external horizontal
defleetion. In this mode,sweepgener-
ator is disabled
and HOR INPUT jaek is
eonneeted
to horizontalamplifier. Signal
applied at HOR INPUT jaek produees
horizontal(X-axis) defleetion.
SWEEP VARI/EXT GAIN Control Fine
sweep
frequeneyadjustment
andexternal
signal
gaineontrol When
SWEEP
RANGE
switeh is set to EXT, this eontroladjusts
gain of horizontal ehanneL Note that
horizontal frequeney response varies
with position of this eontrol (refer to
speeifieations).
CRT Gratieule- Gratieule is made of
aerylie resin and hasengraved
markitrgs,
both eoarseand fine, to aid in measuring
waveform on CRT sereen. There is also
a dB sealeon the gratieule,indexedat 0,
-3, -6, -10,
and
-20dBandREF. Ampli-
tude from REF to 0 dB is 6 divisions.
These graduations are eonvenient for
frequeneyresponse
m
easurem
ents.
L4. SYNC INT-BXT Switeh. In lNTernal syne
position, sweepis synehronized
to output
of vertieal amplifier, whieh is also the
waveformbeingobservedon CRTsereen.
In EXT position,
sweep
issynehronized to
signal applied to EXT SYNC jaek. For
synehronized waveform display, this
signal m
ust have a time relationship to
signalbeingobserved.
BOTTOIIIPANEL CONTROII;
15. DC BALANCE Control DC balanee
adjustment for vertieal amplifier. This
adjustment should be set for ze?o or
minimumvertieal movement
of traee as
V GAIN eontrol is rotated from full
eloekwiseto full eountereloekwise
(with
V ATT set to GND).
16. HOR GAIN Control Horizontal ampli-
fier ealibrationadjustment.
L2.
Y
v
13.
v
8.
9.
10.
11.

CONTROI^S
AND INDICATORS!
v REAR PANEL CONTROTS
L7. INTENSITY ContrcL Adjusts brightness
of traee.
18. POCUS Control Adjusts elarity of
trace.
19. Z AXS Terminal Input terminal for
, intensity modulation. Thisjaek requires
an ae voltage or pulse
of approximately
25 V p-p to blank the sereen. Positive
portion of signalinereases
intensity, and
negative portion reduees intensity or
blanks
sereen.
20. GND Terminal Earth and ehassis
ground.
2L. V DIB Terminal Direet defleetion input
terminaL An external signal ean be
routed direetly to CRT vertieal deflee-
tion plates
by eonneetion to this terminal
(eonneet
signal eommonto the adjaeent
GND terminal), and setting DIR-NOR
switeh
to DIR. Sensitivity
is10voltsper
division.
DIR-NOR Switeh. Seleetsinput to CRT
vertieal deflection plates. In NORmal
position, output of vertieal amplifier is
eonneetedto vertieal defleetion plates
for normal oseilloseopeoperation using
VERTINPUTjaek. In DIReet
position,
V
DIR and GND input terminals are eon-
neetedto vertieal defleetion
plates.
CBT AfrJ. Tlaee rotation adjustment.
Loosenand rotate CRT to eorreet traee
tilt.
Power Ccd.
22.
23.
24.
rI'
rt

EIRCIITT DESCRIPNON v
BLOCK DIAGBAM ANALYSXS
Refer to Fig. 2, whieh is a bloek diagramof
the oseilloseope.
The vertieal ehannel eireuits inelude the
vertieal attenuator and vertieal amplifier.
The VERT INPUT signal is applied throughthe
AC-DC switeh, whieh seleets eapaeitive or
direet eoupling,
Md through the V ATT (verti-
eal attenuator) to the vertieal amplifier. The
vertieal amplifier is a highly stable, direet-
eoupled
differential amplifier with a gain of
approximately
61 dB, giving a maximum
sensi-
tivity of approximately 10 mV per division.
The vertieal attenuator andvertieal gaineon-
trol reduee the signal when lessoutput is re-
quired. Theoutput of the vertieal amplifier is
appliedto the vertieal defleetion platesof the
CRTwhen
the NOR-DIR
switehisset to NOR.
When
the NOR-DIR switeh is set to DIR, the
output of the vertieal amplifier is diseonneet-
ed and a signal from the V DIR and GND ter-
minals is applied direetly to the vertieal de-
fleetion plates.
The horizontal ehannel eireuits inelude a
sweep generator for a time base and a hori-
zontal amplifier. The reeurrent type sweep
generator is a free runningsawtooth oseillator
whiehproduees
the sweepwaveform. Its fre-
queney range is seleeted by the SWEEP
RANGEswiteh, and fine frequeneyeontrol is
provided by the SWEEPVAR eontrol The
INT-EXT switehseleets
the synesignal
for the
sweep
generatorfrom the vertieal ehannel,
or
theEXTSYNC input.
The sawtooth wave is amplified by the
horizontal amplifier and applied to the hori-
zontal defleetion plates of the CRT. The
horizontalamplifier is a stable,
direet eoupled
differential amplifier with a gain of approxi-
mately 35 dB. The horizontal amplifier may
also be used to amplify an external signal
appliedat the HOR INPUTjaek. In this mode,
the EXT GAIN eontrol allows the gain. to be
varied
by about10dB.
The power supply provides operating volt-
ages for all eireuits. The regulated +15
V'
-15V, and-6 V sourees
are used
in the vertieal
preamplifier and sweep generator eireuits.
thg +170V souree
is used
in the vertieal and
horizontal final amplifier stages. The high
voltage souree provides about -1400 volts
aeeeleration
voltage for the CRT beam. The
Z-axis input is applied to the eontrol grid'
where it may be usedas intensity modulation
of the CRTbeam.
YEBIICAL CHANNEL CIRCI'NS
Refer to Fig. 3 for a simplified diagram
of
the vertieal ehannel
eireuits and to the sehe-
matie diagram in the rear of the manual for
full eireuit detaills.
Input Cireuit ;
The vertieal input signal is first routed to
the AC-DC eouplingswiteh, 53. Switeh S3
seleetsor bypasseseapaeitor Cl. In the AC
position, Cl is eonneeted
in series with the
input. In the DC eoupling
position,eapaeitor
Cl is bypassed
and the input signal is eoupled
direetly to the attenuatorswiteh.
Vertieal Attenuator
Thebasiesensitivityof the vertieal ehannel
is 10 mV/division. The vertieal attenuator
expands the input range by offering three
sensitivity stepsof 10 mV/div, 0.1V/div' and
1 V/div. This is aehieved
by voltage divider
networks, seleeted by S1a and Slb' whieh
attenuate the input to the vertieal preampli-
fier by Xl (direet), X10, or X100. Trimmer
eapaeitors
TC101
andTC102
provide
frequen-
ey eompensation
for the XL()and X100steps'
to mateh the Xl step. A eonstant
inputimpe-
danee
of 1 Megohm
is maintained
in all steps.
A fourth step of switeh S1 opensthe VERT
INPUT path and grounds the input of the
vertieal preamplifier. This establishes a v
eonvenient
0-volt referenee.

CIRCTITT
DESCRIPTION
v
|} Fig. 2. BloekDiagram.
Vertieal Preamplifier
The vertieal preamplifier is a direet-
eoupled differential amplifier made up of
three stages, an FET input amplifier Q101-
Q103,
a buffer stageQ104-Q105,
anda tran-
sistor
amplifier
stage
Ql06-Ql09.
The first stage is an FET input amplifier,
Q101-Q103,
whieh presents a very high input
impedanee. It has negligibleshuntingeffeet
on the 1 Megohm
input resistanee. Thesignal
side of Q102 establishes the internal de bal-
anee for the entire vertieal amplifier board.
VR101 (OC BAL) allows adjustment of de
balanee. FET Q101 provides input voltage
overload
proteetion and FET Q103
establishes
signal groundfor Q102
andsueeeeding
ampli-
fier stages.Q102 and
Q103
aresouree
eoupled
in a differential amplifier eonfiguration; the
input signalappliedto Q102 is eoupled
to the
soureeof eommon
gate
FET
Q103.
rt In the seeond
stage
of the vertiealpreamp-
lifier, Q104
and
Q105
areemitter-followers
to
Q102 and Q103. These transistors aet as
impedanee eonverters, eonverting from the
very high impedanee
of the FETrsto a low
impedanee drive signal for the transistor
amplifier.
Q106-Q109
form the third stage of the
vertieal preamplifier. Vertieal gain(V GAIN)
is eontrolled
by front panel
potentiometer
VRl
whieh limits the eurrent fed to the bases
of
Q10S
and Q109. Stability of Q106-Q109
is
maintainedthrough the useof negativefeed-
baek provided by C132 and R178. Signal
output voltage is developed
aerossresistors
RL22
andR123
from emitter euments
of Q108
andQ109
andfed to the final amplifier' Q110
and
Ql11.
Ventieal Final Amplifien
The vertieal final amplifier stage ineludes
differential amplifier Q110
andQl11.. A high
frequeney eompensation'network may be
trimmedby adjustment
TC103
to aehieve
the
CRT
V.AMP
Ol01l,0111
H.
AMP
0114-Q116
SWEEP
NERAT
EXT 01
12.
01
13
EXTSrYrC
HOR
I]IPUT +15V+170V
POWER
SUPPLY

CIRCIIIT DESCRIPITON
5 MHz bandwidth. Front panel vertieal posi-
tioning. is aeeomplished by potentiom eter
VRz, I eOS, asit shifts the de biasof Q110
and Q111. The vertieal defleetion plates of
the CRT are fed from the eolleetorsof Q110
and Q111,
when
NOR-DIRswitehSS is set to
NOR. At this point, the waveform is about10
volts per division.
With NOR-DIR switeh 55 set to DIR, the
vertieal defleetion plates of the CRT are
eonneeted
direetly to the V DIR terminal and
ground.
A sample of the vertieal final amplifier
output is available to the horizontal ehannel
eireuits for internal syne.
HOruZONTAL CHANNBL CIBCITrIII
Refer to Fig. 4 for a simplified diagram of
the horizontal ehannel eireuits and to the
sehematie
diagram at the rear of the manual
for full eireuit details.
SweepGenerator
The sweep generator eireuit eonsistsof a
reeurrent sweep sawtooth oseillator built
around
transistors
Q112
andQ113.
The frequeney at whiehthe sawtoothoseil-
lator operates
is determinedby the RC time
eonstant of the eomponents in the emitter
eireuitof Q113
(Ca, C4,C5, VR4and
R141).
SWEEP
RANGEswiteh,32,
seleetsthe eapaei-
tanee eomponentof the RC eireuit: when
set
to the 10-100
position,
C3 is seleeted,
provid-
ing a eapaeitanee
of 0.47
UF;
whenset to the
100-1k position, C4 is seleeted,
providing
a
eapaeitanee
of 0.047
pF;whenset to the 1 k-
10k position, C5 is seleeted, providing a
eapaeitaneeof 390 pF; and, when set to the
10k-100
k position,the stray eapaeitanee
of
the eireuit is seleeted. In eaeh ease, the
SWEEP
VARI/EXT GAINeontrol,VR4,and its
series resistor R141, are seleeted as the
resistanee
eomponent
of the RC eireuit. The
RC time eonstant is greatest when VR4 is
fully eountereloekwise
and its resistanee is
highest. TheRC time eonstantisredueedand
the sweep frequeney is inereased
as V.R4is
turned
eloekwise.
Fig. 5 is a partial sehematie
diagram
of the
sweep generator eireuit with waveforms to
helpillustrate operation
of the eireuit.
First, let us eonsider the free running
manner of operation where no syne signal is
applied. During the negative-going ramp
portion of the sweep waveform (at Ql13
emitter), Q112eonduets
and establishes
a de
voltage at the base of Q113,eutting it off.
With Q113eut off, the seleeted
sweep
range
eapaeitor eharges toward -15 volts through
VR4 and R141. The rate of ehargeis deter-
mined by the RC time eonstant
as previously
deseribed. As the eapaeitor eharges, the
voltage at the emitter of Q113
ramps nega-
tively. The voltage eontinues
to ramp nega-
tively, whiehdeereases
the bias
on Q113, until
the threshold
of eonduetion
isreaehed.
The negative-going ramp ends when the
threshold of eonduetion
of Q113 is reaehed.
Q113 eonduets and quickly diseharges the
sweep
range eapaeitor to the de value estab-
lishedby the voltage divider of R138,
Q113,
VR4, and R141. This eonduetion
of Q113
develops a negative pulse at the eolleetor,
whieh is fed baekthroughC108
to the baseof
Ql12, cutting it off. TheRC time eonstant
of
C108 and R135 determine the eutoff period
for Ql12. This is the very short interval when
the sawtoothwaveformreturnsto its positive-
most point. Thenegativepulse at the baseof
Q112 is inverted to a positive pulse at the
eolleetor, and is direetly eoupledto the base
of Q113 to eontrol the sweep
eapaeitor
dis-
eharge
period. At the endof this pulse,
Q113
is again eut off, and the next negative-going
ramp begins. This eyele is eontinuously
re-
peated. The sawtooth waveform ramps from
approximately +2 volts to -2 volts, and is
limited to the mostlinearportionof the sweep
eapaeitorehargeeyele.
Now let us eonsider
eireuit operationwhen
a syne signal is applied. Refer again to the
waveforms in Fig. 5. Syne
signals
are fed to
Q112,
superimposed
on the sweep
reset pulse,
invertedand applied
to the baseof Q113. A
negative-going
edge
of the syne
input signal
is
inverted to a positive-going
edgeat the base
of Ql13. If this superimposed
positive edge
oeeursjust before the end of a free-running
sweep, it will bias Q113 into eonduetion
and
b
a
Yt

CIRCUIT DBSCRIPTION
v
ft
VERTICAL PREAMPLIFIER
FET AMPL BUFFER TRANSISTOR
AMPL
o lol
Q
t02
Q
ro3
S
I POSITIONS
r (sHowN)
t/to
t/ too
GNO
VERTICAL
FINAL AMPLIFIER
end the sweep,thus loeking the sweepinto
synehronization with the waveform being
observed.
Fig. 5 shows lrow synehronization
oeeurs
with three
eyeles
of square
wave
displayedand
usedfor internal syne. The first two eyeles
have no effeet, sinee the sweep is not yet
approaehing the threshold of eonduetion.
However,
the negative
edge
at the endof the
third eyeleof syneinput (inverted
to a posi-
tive edge
at thebaseof Q113) eauses
Q113
to
reaeh the threshold of eonduetionslightly
soonerthan in the free runningstate. The
same prineiple applies for displaying and
synehronizing
more or less
than three eyeles,
and for sine wavesor other types of
.
wave-
forms. The SIVEEP
RANGE seleetionand
lNoRl
:55
SWEEP
VARIadjustmentmust
firstbe
set
to a
point near synehronization;then the syne
signal loeks the sweepinto synehronization.
Aetually,for proper
syneronization,
theperiod
of the sweep
generator
(in its free running
state) must be a little longerthan the tirne
between
syne
pulses
(or
some
multipleof syne
pulses
whenmore
than
oneeyeleisviewed).
SyneCireuit
The syne signal may originate from the
vertieal ehannelor an external syne .signal
applied
at the EXT SYNC
jaek. One
or the
other
maybeseleetedbythe
INT-EXTswiteh,
54. The seleeted
synesignalis eapaeitively
eoupled
through
C107
andelampedto the de
levelof Q112 base
by
diodeD101.
vR rol
bcBAn lvGArN
I
ml
I
c6f
tvDrRl I
-@-)
R3
+I7OV INT
SYNC
TO
SWEEP
GEN
Fig. 3. Vertieal
Channel
Cireuits,SimplifiedDiagram.
CRT
6
Rr23
Rt
30
HI FREO
COMP
v

CIRCUIT DE.SCRIPIION
FET Buffen
FET buffer Q114 serves as a high input
impedanee,low output impedanee
stage be-
tweenthe sweep
generator
andthe horizontal
finalamplifier. In sweepoperation,
FET
Q
114
prevents "loading" of the RC eharge time
eonstantramprate.
Horizontal Amplifien
The horizontalfinal amplifier is eomposed
of a two transistor push-pull output stage,
Ql15 and Q116. Horizontal
positioning
of the
traee is provided by VR3 (<>POS eontrol on
the front panel) as it ehangesthe dc bias
suppliedto the baseof Q116. Thegain
of the
horizorrtalfinal amplifier is preset
by internal
adjustment VR102, as it sets the limit of
emitter eurrentavailablefor Ql15 and
Q116.
The voltage outputs of Q115 and Q116 are
developed
aerossR149and R150and applied
to the horizontal defleetion
plates
of the CRT.
EXTERNAL HORIZONTAL OPERATION
When
SWEEPRANGE
switeh
52 isset fully
eloekwise to the EXT position, the sweep
generator is disabledand an external signal
applied
at the EXT SYNC/HOR
INPUT jaek
provides horizontal defleetion of the CRT
beam. Thismode
of operationis often ealled
X-Y operation,as the horizontal input pro-
dueesX-axis (horizontal)
defleetion,and the
vertieal input produees Y-axis (vertical)
defleetion.
Refer to Fig. 4 for a simplified eireuit
diagram,
or to the sehematiediagramfor full
eireuit details. In this mode of operation,
switeh 32 entirely diseonneets
the sweep
generator
from Q114. TheSWEEP VARI/EXT
GAINeontrol,VR4,is eonneeted
between
the
FIORINPUT
jaek andFET buffer Q114. VR4
beeomesthe Horizontal Gain eontrol, as it
determines
thelevelof signal
appliedto Ql14.
At maxim um gain (no attenuation),the hori
-
zontal
ehannelsensitivity
isabout300mVper
division. V.R4is eonneetedto provide
a eon-
stant input impedanee
of 1 megohm. Q114
presents
negligible
shuntingimpedanee,simi-
lar to Q102 in the vertieal ehannel.. The
output
of Ql14 is amplified
by the horizontal
final amplifier, Ql15 and Ql16, just as in
sweep operation, exeept that the external
horizontal signalis beingamplified insteadof
the sweepsawtooth
signal.
LOWVOLTAGE POITBRSUPPLY
Refer to the sehematic
diagramat the rear
of the manual for eireuit details.
The power transformer has two primaries
whieh may be wired in parallel for Ll? VAC
operation,or in series
for 230VAC operation.
Taps also permit wiring for 100 VAC opera-
tion. Neon lamp Nl and resistor R15? are
eonneetedaerossa 100-volt segmentof the
primtrV, eausingthe lamp to light whenever
POWERswiteh
S106
isON.
A eenter-tapped
seeondary
winding of the
power transformer provides power supply
souree
voltages
of 25volts and160volts rms.
Bridge reetifier D104 provides full wave
reetifieation, andis eonneeted
to provide
both
positive and negative de voltages. C116and
C
117 provide filtering, and Zenerdiode D105
regulates the positive side of the bridge to
+15
volts. C119 and C120provide filtering,
and Zener diode D106regulates the negative
side of the bridge to -15 volts. In addition,
the raw de from the negative side of the
reetifier is also dropped through Rl55 and
regulated to -6 volts by Zener diode D109.
Theseregulated voltages are the rrelean
sup-
plies", providing low noise
operationof sensi-
tive, high gain stages in the vertieal and
horizontalehannels.
A +170volt supply
provides
the operating
voltage for the vertieal and horizontal final
amplifiers. Full wave reetifier diodesDl02
and
D103
eonvert
the 160volt rms
output
(225
volt peak) of the power transformer to de,
whiehis filteredby C114
and
C115,
providing
approximately
+170
volts.
Y
*
IIIGH VOLTAGESUPPTY
The high voltage supply providesaeeeler-
ation voltage for the CRT beam. The high
r
voltage
isderivedfrom the 500volt winding
of
10

CIRCTIIT DESCRIPIION
v
v
SWEEP
GENERATOR
at
c4
HMIZONTAL
FINAL
AMPLIFIER
INT SYNC
FROM VERT
A
MPL
it-._*
c5 v
(--{
.,9
---lt----' o
SYNC
CIRCUIT
S2 POSITIONS
ro-roo
(sHowN)
roo
-rK
lK
- roK
roK
-roox
EXT
VR
IO2
I-noR
GAINI
Fig.4. Horizontal
Channel
Cireuits,
SimplifiedDiagram.
Fig.5. SweepGenerator
Cireuit Diagramand
lVaveforms.
the power transformer. A voltage doubler,
eomposed
of high voltage diodes D107 and
D108, and eapaeitors
C124,C12
5 and C126,
eonvertsthe 500volt ae into -1400 volts de.
Filtering for the high voltage supply is pro-
vided by eapaeitor
C123. The -1400
volts is
oilz
Qil3
FREE
RUNNING_ NO
SYNC
APPLIED
Qil5
EMITTER
Qil3
COLLECTOR
Q
ll3
EASE
SAWTOOTH
4",
WITH SYNC APPLIEO
S
YNC
sTGNAL
J U m
[l*€Etl
I vanr I
VR4
Q
ll3
EMITTER
oil3
COLLECTOR
Qil3
BASE
___{€
I co o\sz
-v
*-1---lt------o \
lcse
H+e
v
11

SNCIIIT DESCRIPIION
appliedaeross
a voltage divider network eon-
sistingof R159-R161,
VR103' R162' R163'
R165,
andR166. The eontrol grid voltage is a
fixed de high voltage availablefrom the volt-
age divider network. Part of the vol_tlg_!
0fuider network is paralleled by INTENSITY
eontrol VR104. VR104adjusts
the voltage at
the eathodeof the CRT with respeet to the
eontrol grid voltage, thus varying brightness.
Beeause
the anodeis grounded,
I total aeeel-
erating potential of 1400volts is used. The
voltage divider network also ineludesFOCUS
eontrol VR103. It seleetsa somewhatlower
voltage to be applied to the foeus grid of the
CRT.
A final winding of the power transform
er
provides
6.3 volts ae to the CRT filament. To
prevent a high potential differenee between
the filament and eathode of the CRT' the
6.3volt windingis floated to the high voltage
supply.
A signal aPPtiedat the Z AXIS INPUT
terminal is eapaeitivelyeoupled
through CLZL
to the eontrol grid of the CRT. A signal
of 25
volts amplitude or more will intensity modu-
late the CRT
beam.
b
3
L2
i,

vADJUSTTTIENTS
FUSE
@trF-Cta
Printed
circuit
board 6
TC
lol
VR
101 @
DC BAL
6
TC1
01
VR102
a
@
HOR.GAIN
TC1
02
@o
Fig. 6. Loeations
of Adjustments.
v
WARNIilG
The CRT socket and cerAainpolnts
on the circuft board carry high
rnltoges of apprcximately -1400 V
cnd +170 lplts. Obsente the high
wltage sofety prccoutions listed on
the inside front coven
ADJUSTfrTENT
OF DC BALANCE
1. Allow at least 15 minutes of warm up
time for the unit to stabilize before
makingthis adjustment.
2. Setthe operating
eontrols
asfollows:
SWEEP
RANGE
to any
position
exeept
EXT.
V ATTswitehto GND.
I
i POSITION
eontrol to eenter traee
vertieally on CRT.
'- 3. With no signalapplied,
a traee shquld
be
present
onthe CRT.
Rotate the V GAIN eontrol baek and
forth from oneextremeto the other, and
observe
if the traeeshifts upand
down.
If the traee shifts in step 4, adjust DC
BAL trimmer VR101
for minimum
shift-
ing of the traee asthe V GAINeontrolis
rotated. For easiest adjustment' start
with the V GAIN eontrol fully eounter-
eloekwise. Repeat adjustm
ent until
shifting of the traee is minimized.
VRl01 is aeeessible
through
a holein the
bottom of the ehassis
as
shown
in Fig. 1 -
or - the top easemay be removed,and
VRl01 isloeatedas
shown
in Fig.6.
ADJUSTDIENT
OF HORIZONTAL GAIN
Preferred illetlpd
This method of adjustment ealibrates the
external horizontal sensitivity to 300
mV/
division.
1. Setoseilloseope
eontrols
asfollows:
SWEEP
RANGE
switeh
to EXT.
4.
13

ADJUStrMENTlI
b
Fig. 7. Effeets of HOR GAIN Adjustment
VR104.
SWEEP
VARI/EXT GAIN eontrol fully
eloekwise.
V ATT switehto GND.
? POSto eenter the traee vertieally.
2. Apply a ealibrated 3 V p-p sine wave or
squarewave at 1 kKz (with no de offset)
to the EXT SYNC/HOR INPUT jaek.
Conneet the signal eom
mon to the J
jaek.
3. Adjust HOR GAIN trimmer VR102for a
horizontal defleetion of 10 divisions.
VR102is aeeessible
througha holein the
bottom of the ehassis
(see
Fig. 1). If the
ease is removed, VR102 is loeated as
shown
in Fig. 6.
Alternate ilethod
This method of adjustmentsets the sweep
length for 10 divisions horizontal defleetion,
but external horizontal operation is uneali-
brated" Theeffeets of HOR GAIN adjustment
areshownin Fig. 7.
1. Setoseilloseopeeontrolsasfollows:
SWEEPRANGE
switeh
to any
position
exeeptEXT.
SWEEP
VARI/EXT GAIN eontrol fullY
eloekwise.
V ATT switehto GND.
i POS
to eenterthe traee vertieally.
2. A traee should
be displayed
on the CRT.
3. Adjust+POS eontrol sothe beginningof
the traee is visible, and alignedwith one
of the gratieule markers near the left
edgeof the CRT sereen.
4. Adjust HOR GAIN trimmer VR104for a
traee length of 10 divisions. VR102 is
aeeessible
through a hole in the bottom
of the ehassis
(see
Fig. 1). If the ease
is
removed, VR102 is loeated as shown in
Fig. 6.
TRACE ROTAIION ADJUSTUENT
The earthts
magnetie field and other mag-
netie fields may eause
the traee to tilt when
the oseilloseope
is movedfrom oneloeation to
another. This adjustmentrotates the CRT to
eomeet
for traee tilt.
1. Setthe operating
eontrols
asfollows:
SWEEP
RANGEto anY
Position
exeePt
EXT.
V ATT switehto GND.
2. With no signalapplied,
a traee should
be
present on the CRT. Adjust the POS
eontrol to eenter the traee vertieally on
the CRT. The traee should
be parallel
with the horizontal gratieule line. If
traee tilt is noted, make the following
adjustment.
3. Refer to Fig. 8. Loosen
the two serews
a
b
L4
Length of
horizontal
def lection
Larger
H. GAIN Smaller
H.
GAIN

ADJUSTMENTS
v
It (A) holding the CRT mounting plate at
the rear.
4. Plaeea wide blade serewdriverinto slit
(g) to turn the CRT mounting
plate, until
the traee is parallel with the horizontal
gratieuleline.
5. Carefully tighten serews (A), observing
that the traee does
not rotate whenthe
serews
aretightened.
FREQUBNCY COMPENSATION
ADJUSTMENTS
1. Remove
the ease from the unit.
2. Setoseilloseopeeontrolsasfollows:
V ATT switehto 1 (10
mV/DIV).
V GAIN eontrolfully eloekwise.
SYNCswiteh
to INT.
SWEEPRANGEswitehto 100-1
k.
3. Appty a 1 kHz square
waveto the VERT
INPUT
jaek. Conneetthesignaleommon
to the jaek. Terminatethe square
wave
It generator into its eharaeteristie impe-
o@ @a
Fig. 8. Tlaee RotationAdjustment.
4.
danee(i.e., for a square
wavegenerator
with anoutput
impedanee
of 50
ff termi-
nate into 50n).
Adjust the output level of the square
wave generator for a waveform ampli-
tudeof 6 divisionsonthe CRTsereen.
Adjust the SWEEP VARI/EXT GAIN
eontrol to displaytwo to four eyeles
of
the squarewave.
Adjust tne $ POSand
+ POS
eontrols
to
position thd display
in the eenter of the
CRT.
Adjusttrimmer eapaeitor
TC103
for the
most ideal square wave waveshape,
as
shownin Fig. 9.
If desired, il additional
eheekfor proper
adjustment
of high frequeney
eompensa-
tion trimm
er TC103 may be rnadeas
follows. Conneet a sweep generator
having a flat response
from 1kHz to at
least5 MHz to the vertieal input. Adjust
the sweep generator to sweeP from
1 kHz to 5 MHz andexternallysynehron-
ize the oseilloseope
sweep
to the trigger
outputof the sweep
generator. Thefre-
5.
6.
1.
15

ADJUSTMENTS
\-
I
__t__
h
I
I
a
queney
response
eurve will be displayed
on the CRT. Adjust
thesweep generator
output
levelfor 6 divisions
amplitude
on
the CRT at the low frequeney
(t kHz)
referenee.
Adjust
TCt03 for the flattest
frequeney
response,
withno
sharp
dips
or
peaks,
and
sothat amplitude
at 5 NlHz is
at least
4.2divisions
(-3
dB).
Next,
set the V ATT switeh
to L/10 and
inerease the output of square wave
OYERCOI{P
EN
SAT
ION
Overshoot
l"/ol
= bla x 100
T'I{D€RCOilPE
il SATIOil
Fig. 9. Frequeney
Compensation
Adjustments.
=
generator to again obtain an amplitude
of 6divisions.
9. Adjust trimmer eapaeitor TCl02 to
mateh
thewaveform
obtained
instep
7.
10. Now,
set the V ATTswiteh
to 1/100
and
' againinerease
the output of the square
wave
generator
for 6 divisions
amplitude.
11. Adjust trim
mer eapaeitor TCl01 to
' mateh
thewaveformobtained
in
step?.
I
8.
t>
16