HP 211B Service manual

Re]
OPERATING AND SERVICE MANUAL
MODEL 211B
SQUARE WAVE GENERATOR
SERIALS PREFIXED: G 621
COPYRIGHT HEWLETT-PACKARD GMBH !I966
BOBLINGEN, WESTERN GERMANY
PRINTED: JUNE , 66
o02iI - 90000

Table of Contents
TABLE OF CONTENTS
Section ; Page
I GENERAL INFORMATION. ......... 1-1
1-1. Description. ............. 1-1
1-4. Manual Identification. ........ 1-1
II INSTALLATION. .............. 2-1
2-1. InitialInspection........... 2-1
2-4. Claims and Repacking........ 2-1
2-7. Preparation for Use......... 2-1
2-10. Installation. ............. 2-1
2-12. Rack Mounting. ........... 2-1
II OPERATION. .........-2+082806458 3-1
3-1. Introduction. ............ 3-1
3-3. Duty Cycle. ............. 3-1
3-6. Operating Procedures........ 3-1
3-8. Free Running Mode........ 3-1
3-10. Sync Signals. ........... 3-1
3-12. Trigger Output.......... 3-1
IV. PRINCIPLES OF OPERATION. ....... 4-1
4-1, Introduction. ............. 4-1
4-3. General Description. ........ 4-1
4-9, Schematic Theory......... 4-2
4-10. Frequency Control Network. . . . 4-2
4-12. Current Source. .......... 4-2
4-13. Switching Circuit.......... 4-2
4-14. Ramp Capacitor Amplifier. .... 4-2
4-15, Schmitt Trigger. ......... 4-3
ii
Model 211B
Section Page
4-16. Syne Input Cirevit.........2.. 4-3
4-17. Trigger Output Circuit........ 4-4
4-18. 6002 Amplifier. ........... 4.4
4-19. 502 Amplifier... .......... 4-4
4-20. Power Supply. ............ 4-4
MAINTENANCE. ............0.. 5-1
5-1. Introduction. ............. 5-1
5-3. Test Equipment............ 5-1
5-5. Instrument Cover Removal. ..... 5-1
0-7. Performance Check.......... 5-1
5-9. Repetition Rate. .......... 5-1
5-10. Symmetry Control Check. .... 5-3
5-11. Output Pulse Characteristics. . . 5-3
5-13. 902 Output... .. Hes atl oe Shs hs 0-4
5-16. 6002 Output... ......04, 5-4
5-19. Synchronization... ........ 5-5
5-21. Trigger Output. .......... 5-5
5-23. Power Supply. ........... 5-6
5-25. Troubleshooting. ........... 5-6
5-28. Repair and Replacement. ...... 5-6
5-30. Component Identification. .... 5-6
5-34. Servicing Etched Circuit
Boards: . 06 ses ee See ee 5-6
REPLACEABLE. ............ . 6-1
6-1. Introduction.............. 6-1
6-3. Ordering Information......... 6-1

List of Illustrations and Tables
LIST OF ILLUSTRATIONS
Model 211B
Number Title Page
"1-1. Model 211B Square Wave Generator, ... 1-1
2-1. The Combining Case............ 2-0
2-2. Steps to Place Instrument in Combining
CASE? ie ave fark Geko ar els sel dS 2-0
2-3, Adapter Frame Instrument Combinations. .2-1
2-4. Two Half Modules in Rack Adapter. .... 2-2
3-1. Definition of Output Pulse Characteristics. 3-1
3-2, Front Panel Description. ......... 3-2
4-1. Basic Block Diagram. ........... 4-1
4-2. Simplified Current Source Operation. . . . 4-2
4-3. Ramp Capacitor Amplifier Block Diagram. 4-3
4-4. Synchronizing Operation.......... 4-3
Number Title Page
5-1. Definition of Output Pulse Characteristics. 5-1
5-2. Dial Accuracy Check. ........... 5-3
5-3. 502 Output Pulse Check. .......... 5-4
5-4, 6002 Output Pulse Check.......... 5-4
5-5. External Pulse Synchronization. ..... 5-5
5-6. Trigger Output Pulse Check........ 5-5
5-7. Component. Location on A2 Board. ..., 5-8
5-8. Repetition Rate, Synchronizing and Trigger
Output Circuit Schematic Diagram. 5-9/5-10
5-9. Power Supply Circuit Schematic Diagram. 5-11
5-10. Component Location, top view...... 5-12
5-11. Output and Attenuator Circuits Schematic
Diagrams i350 es bs wow eee ke. So we 5-13
LIST OF TABLES
Number Title Page
1-1. Model 211B Specifications. ........ 1-0
5-1. Required Test Equipment.......... 5-2
5-2. Dial Accuracy. ........6.2.50+02e005 5-3
Number Title Page
5-3. Schematic Diagram Notes.......... 5-7
6-1. Reference Designation Index........ 6-2
6-2. Replaceable Parts............ . .6-8
Hii

Specifications
Model 211B
Specifications
50 and 600 ohm Outputs
SYMMETRY CONTROL: Continuously variable from
25% - 75% duty cycle.
POLARITY: Negative 6
PHASE DIFFERENCE: 180° between 502 and 600Q
outputs at 50% duty cycle.
50 ohm Output
SOURCE IMPEDANCE:
approximately 15pF.
PULSE SHAPE: (Measured at 5 V across 502)
RISE AND FALL TIMES: < 5ns .
OVERSHOOT AND RINGING: < 5% peak of pulse
amplitude.
PRESHOOT: <5%
502 +*3% shunted by
AMPLITUDE
MAXIMUM OUTPUT: 5V across 502, 10V
across an open circuit. Output circuit protec-
ted, cannot be damaged by shorting.
ATTENUATOR: Provides 7 steps from 0.05 to
5 Vinal, 2.5, 5 sequence.
VERNIER: Provides continuous adjustment be-
tweenranges, minimum output less than 0.02V
across 502. Rotating vernier to minimum
(ccw) may increase preshoot to 10%.
600 ohm Output
SOURCE IMPEDANCE: 6002 410%
PULSE SHAPE
RISE AND FALL TIMES: < 70ns across
6002, less than140ns across anopencircuit.
Decreased amplitude setting will improve
rise time.
OVERSHOOT AND RINGING: < 5%
AMPLITUDE
MAXIMUM OUTPUT: 30 V across 6002, 60 V
across an open circuit.
ATTENUATOR: Providescontinuous adjustment
from full output to less than 0.3 V across
6002.
1-0
Repetition Rate and Trigger Output
FREE RUN
REPETITION RATE
502 output: 1 Hz to 10 MHz, 7 ranges
6002 output: 1 Hzto 1MHz, 6 ranges
DIAL CALIBRATION: 1 - 10 (linear)
DIAL ACCURYCY: +5% to 10 MHz at 50% duty
cycle. Variation of symmetry control may
change frequency and additional +5% (10% on
10 MHz range).
PERIOD JITTER: < 0.2% at any duty cycle and
repetition rate setting.
SYNCHRONIZATION
SYNC INPUT: DC coupled, sine waves or positive
pulses from 1 Hz to 10 MHz. Frequency of
synchronizing signal must be 105% - 140%
of dial setting.
SENSITIVITY: Willsynchronizeon positive pulses
of at least 1 V, sine waves of at least 2V
peak to peak.
INPUT IMPEDANCE: Approximately 5002
TRIGGER OUTPUT PULSE: (suitable for synchroni-
zation with another 211B).
WIDTH: 10 (+5) ns at 50% points.
AMPLITUDE: At least 2 V across 502
TIMING: Coincident with leading edge of 502 pulse
POLARITY: Positive or Negative
General
POWER: 115 or 230 V 10% - 15%, 50 Hzto 400 Hz,
23 W.
DIMENSIONS:
WEIGHT: Net, 9ibs (4kg). Shipping 11 lbs (5kg)

Model 211B
Section I
Paragraphs 1-1 to 1-5
SECTION |
GENERAL INFORMATION
1-1. DESCRIPTION.
1-2. The -hp- Model 211B Square Wave Generator
(shown in Figure 1-1) is a compact, general purpose
instrument providing negative pulses of variable fre-
quency, symmetry and amplitude. Complete specifi-
cations of performance are given in Table 1-1. Two
independent outputs are available. The 502 source
supplies pulses with 5ns rise and fall times and a
peak output of 5 volts across 502. Simultaneously,
a 6002 source provides pulses of 30 volts across
6002 having a rise and fall time of 70ns. Matched
output impedance provide twice the voltage across
an open circuit. Amplitude for both pulses is
seperately controllable. The frequency range of the
instrument, 1 Hz to 10 MHz, is covered in 7 decade
ranges with a linearly calibrated dial for continuous
adjustment on all positions. The 502 output oper -
ates to 10 MHz, the 6002 output to 1 MHz. The
duty cycle can be varied from 25% to 75%.
1-3. Trigger output pulses, for synchronizing exter -
nal circuits or instruments, have a pulse width of less
than 20ns, reversible polarity and an amplitude of at
ro. Fal 218 SQUARE WAVE
HEWLETT PACKER
least 2 volt across 502. The trigger output is coin-
cident with the leading edge of the 502 output. The
211B operates free running or may be synchronized
with external signals of either sinewaves or positive
pulses,
1-4. MANUAL IDENTIFICATION.
1-5. Information in this manual applies directly to
Modell 211B instruments with serial prefix of G- 621
The serial prefix is the first three digits of the eight-
digit serial number (e. g. 000-00000) used to indentify
each -hp- instrument. If the serial prefix of a Model
211B is not G-621, a manual change sheet supplied
with the manual will define the differences between
that Model 211B and the one described in this manual,
or a different manual will provide correct informa-
tion. Corrections to this manual, due to errors that
existed when it was printed, are called Errata and
appear only on the change sheet supplied. To obtain
correct manual information for any instrument, con-
tact the nearest Hewlett-Packard Company Sales/Serv-
ice Office and always specify the model number and
serial number.
Figure 1-1 Model 211B Square Wave Generator
1-1

Model 211B
Section II
Figure 2-1 and 2-2
DIVIDER ASSEMBLY
DIVIDER LATCH RETAINER
Figure 2-1 The Combining Case
oO
INSERT DIVIDER, ENGAGING
TABS IN TOP AND BOTTOM
MOUNTING SLOTS
@
PUSH
RETAINER
DOWN
TWIST DIVIDER TO VERTICAL TORELEASE
POSITION
©
SLIDE INSTRUMENT
©) : mee INTO CASE
PUSH IN TO LIMIT
@
TO SET RETAINER BACK IN
PLACE, ENGAGE HOOKS FIRST
4) ON ONE SIDE OF DIVIDER,
THEN ON OTHER
SLIDE LATCH TO LOCK
DIVIDER
PUSH RETAINER UP TO LOCK
Figure 2-2 Steps to Place Instrument in Combining Case

Model 211B
Section IT
Paragraphs 2-1 to 2-13
SECTION Il
INSTALLATION
2-1. INITIAL INSPECTION.
2-2. MECHANICAL INSPECTION. If external
damage to the shipping carton is evident, ask the
carrier’s agent to be present when the instrument is
unpacked. Check the instrument for external dam-
age such as broken controls or connectors, and dents
or scratches on the panel surfaces. If damage is
evident, see Paragraph 2-4 for recommended claim
procedure and repackaging information. If the ship-
ping carton is notdamaged, check the cushioning mat-
erial and note any signs of severe stress as an in-
dication of rough handling in transit. If the instru-
ment appears undamaged, perform the electrical
check given in the following paragraph.
2-3. ELECTRICAL CHECK. Check the electrical
performance of the Model 211B as soon as possible
after receipt. Paragraph 5-7 through 5-22contain
performance check procedured which will verify in-
strument operation within the specification listed in
Table 1-1. This check is also suitable for incoming
quality control inspection. If the Model 211B does
not perform within the specifications when received,
refer to Paragraph 2-4 for recommended claim pro-
cedure and repacking information.
2-4. CLAIMS AND REPACKING.
2-5. Ifphysical damage is evident or if the instru-
ment does not meet specifications when received, no-
tify the carrier and the nearest Hewlett-Packard
Sales/Service Office (see list at rear of this manual).
Refer to inside front cover of this manual for the
Warranty statement applicable of all Hewlett-Packard
instruments and products. The Sales/Service Office
will arrange for repair or replacement of the instru-
ment without waiting for settlement of the claim
against the carrier.
2-6. The original shipping carton and packing mate-
rial, with theexception of the accordian-pleated pads,
should beused for reshipment. The accordian-pleated
pads are fatiqued with one use and are not reusable.
The Hewlett-Packard Sales/Service Office will
also provide information and recommendations on
materials to be used if the original packing material
is not available or is not reusable. Materials used
should include: (1) a double walled carton (check
with a freight carrier for test strength required),
(2) heavy paper or sheets of cardboard to protect all
instrument surfaces; use extra material around
projecting parts of the instrument, (3) at least four
inches of tightly-packed shock-absorbing material
surrounding the instrument. Close the carton securely
with heavy paper tape. If the instrument is to be
shipped to a Hewlett-Packard Sales/Service Office
for repair, attach a tag showing owner, model,
serial number and repairs required.
2-7. PREPARATION FOR USE.
2-8. POWER SOURCE REQUIREMENTS. The
Model 211B may be operated from an ac source of
115 or 230 volts (+10%, -15%) at|50 to 400 Hz!Pow-
fer dissipation is approximately 25 watts. With the
instrument power cord disconnected, move the slide
switch (located on rear panel) until the desired volt-
age numbers (115 or 230) arevisible. A narrow blade
screwdriver is recommended to position the slide
switch. The instrument power line fuse (located at
the rear of the instrument above the|power cord re-
ceptalcle) is a 0.5 ampere, slow-blow type for 115 v.
operation and a 0.25 ampere, slow-blow type for
230 v. operation.
2-9. THREE CONDUCTOR POWER CABLE. To
protect operating personnel, the National Electrical
Manufacturers’ Association (NEMA) recommends
that the instrument and cabinet be grounded. The
centre pin on the power cable is the ground connec-
tion. To retain the protection when operating the
instrument from a two-contact outlet, use a three-
conductor to two-conductor adapter and connect the
adapter wire to a suitable ground.
2-10. INSTALLATION.
2-11. The Model 211B is fully transistorized; there-
fore no special cooling is required. However the in-
strument should not be operated where the ambient
temperature exceeds 55° C,
2-12. RACK MOUNTING.
2-13. The Model 211B is a submodular unit that
when used alone can be bench mounted only. However
when used incombination with other submodular units
it can be bench and/or rack mounted. The -hp- com-
bining case and adapter frame are designed specif-
ically for this purpose.
FILLER PANEL
Figure 2-3 Adapter Frame Instrument Combinations
2-1

Section IT
Paragraphs 2-14 and 2-15
2~2
oO)
ADAPTER
SPACER CLAMP
RETAINING SCREWS
Figure 2-4 Two Half Modules in Rack Adapter
Model 211B
2-14. COMBINING CASE. The combining case is
a full-module unit which accepts varying combina-
tions of submodular units. Being a full-module unit,
it can be bench or rack mounted analogous to any full
module instrument, An illustration of the combining
case is shown in Figure 2-1 . Instructions for in-
stalling the Model 211B in a combining case are given
graphically in Figure 2-2.
2-15, ADAPTER FRAME. The adapter frame isa
rack frame that accepts any combination of sub-mod-
ular units. It can be rack mounted only. An illustration
of the adapter frame is given in Figure 2-3. To as-
semble, refer to Figure 2-4 and proceed as follows
a. Place the adapter frame (1) on edge of bench
as illustrated.
b. Stack the submodular units (2) in the frame.
Place the spacer clamps (3) between instru-
ments. ;
d. Place the spacer clamps (4) on the two end
instruments.
e. Push the combination into the frame.
Insert screws (5) on both sides of frame, and
tighten until submodular instruments are se-
cure in frame.
g. The complete assemble is ready for rack
mounting.

Model 211B
Section III
Paragraphs 3-1 to 3-13
SECTION Ill
OPERATION
3-1. INTRODUCTION.
3-2. This section contains the operating instructions
for the Model 211B Square Wave Generator. This in-
strument has been designed for general purpose lab-
oratory requirements withthe ease-of-use as a prime
consideration. Therefore the operating procedure is
quite simple. Figure 3-2 identifies and briefly
describes
the
pupose
of
each
panel
control
and
connector on the instrument.
3-3. DUTY CYCLE.
3-4. Duty cycle is defined as the ratio of duration of
pulse (i.e. pulse width) to the total duration of one
complete cycle. Figure 3-1 shows the relationship
which determines the duty cycle. The time for one
cycle is defined as the period, and the period is re-
lated to repetition rate by: ae 1
Period = Re5- Rate
Thus
the
product
of
pulse
width
and
frequency
mul-
tiplied
by
100
determines
the
duty
cycle
percentage.
3-5. The SYMMETRY control is responsible for the
duty cycle setting; the variability being 25 - 75 % of
the
period.
The
duty
cycle
remains
unchanged
when
external synchronizing signals are applied to the
Model 211B.
PULSE
[~ WIDTH |
AMPLITUDE
| PERIOD =
!
FREQUENCY
4 . -PULSE_WIDTH
%*DUTY CYCLE Sena ot
PULSE WIDTH x FREQUENCY x 100
Figure 3-1 Definition of Output Pulse Characteristics
3-6. OPERATING PROCEDURES.
3-7. The Model 211B canbe operated in two different
modes, free-running or synchronized with external
signals. The procedures are detailed in Paragraphs
3-8 through 3-13.
3-8. FREE-RUNNING MODE
3-9. The Model 211B will generate internally any
repetition rate from 1 Hz to 10 MHz (1 MHz at 600 2
output). The repetition rate is established by setting
the MULTIPLIER selector to any of the seven inter-
nal ranges and then adjusting the FREQUENCY (Hz)
control to the specific rate desired.
To operate proceed as follows :
(a) Push instrument LINE switch on.
(b) Set MULTIPLIER to desired range and adjust
FREQUENCY (Hz) to exact position for frequency
desired.
(c) Adjust SYMMETRY for desired duty cycle.
(d) 502 OUTPUT. Select AMPLITUDE range and
VERNIER setting desired. Note that the cw
position of the VERNIER yields at least that
indicated voltage on the AMPLITUDE selector
switch.
(e) 6002 OUTPUT. Adjust AMPLITUDE setting as
desired. Note that the specified amplitude is
across a 6002 load. Twice the voltage will be
obtained across an open circuit.
3-10 SYNC SIGNALS
3-11. The Model 211B may be synchronized by ex-
ternal signals of either 1 volt positive pulses or 2 V
peak to peak sinewaves applied to the SYNC INPUT
connector. External signals with frequencies of 105%
to 140% of the internal setting of the 211B can be
synchronized. If the 211B is not in synchronism with
an external signal compare dial and range settings
with the frequency of the external signal.
3-12. TRIGGER OUTPUT.
3-13. Trigger pulses are available at the front panel
of the Model 211B. A positive or negative pulse,
selected by TRIGGER POLARITY switch and coin-
cident with the leading edge of the 502 output pulse,
is available at the trigger output connector.
3-1

Section II
Figure 3-2
®
3-2
211B SQUARE WAVE GENERATOR
HEWLETT PACKARD
Ke) |
FREQUENCY (Hz)
100
LINE
PUSH ON/OFF
SYNC.INPUT
(i2) W)
LINE switch. Controls AC power to instrument
and indicates "on" position by glowing red.
FREQUENCY dial. Provides continuous cal-
ibrated control of the output frequency within the
range determined by the MULTIPLIER setting.
FREQUENCY MULTIPLIER switch. Selects the
operating range of the FREQUENCY dial.
SYMMETRY control. Provides adjustment of duty
cycle of output pulses.
AMPLITUDE selector switch. Selects amplitude
range of the 502 output pulse.
AMPLITUDE VERNIER control. Provides contin-
uous adjustment of the 502 output pulse between
settings of the AMPLITUDE selector switch.
Maximum CW position gives at least the voltage
shown on the AMPLITUDE selector switch.
Figure 3-2
SYMMETRY
MULTIPLIER
IK
0 _j-
TRIGGER
OUTPUT
Model 211B
AMPLITUDE
(VACROSS 50.0;
AMPLITUDE VERNIER
OUTPUT OUTPUT
600n 5302
6
0) @) @
OUTPUT -50 connector.
pulse.
Supplies 502 output
AMPLITUDE control. Provides uncalibrated
control of 600Q output amplitude.
C* [TPUT-6002 connector. Supplies 6002 output
pulse.
TRIGGER POLARITY switch. Selects either pos-
itive or negative TRIGGER OUTPUT pulse.
TRIGGER OUTPUT connector. Supplies trigger
output pulse.
SYNC INPUT connector. Input connector for
external synchronizing signals.
Front Panel Description

Model 211B
Section IV
Paragraphs 4-1 to 4-8
SECTION IV
PRINCIPLES OF OPERATION
4-1. INTRODUCTION.
4-2.
This
section
contains
a
description
of
the
theory
of
operation
of
the
-hp-
Model
211B
Square
Wave
Generator.
4-3. GENERAL DESCRIPTION.
4-4,
The
Model
211B
comprises
of
a
frequency
con-
trol
network,
two
current
sources,
a
ramp
capacitor
network,
a
Schmitt
trigger,
a
sync
circuit,
a
trigger
output
circuit
and
output
amplifiers.
The
complete
block
diagram
is
shown
in
Figure
4-1.
4-5.
The
Schmitt
trigger,
current
sources,
and
the
ramp
capacitor
form
the
basic
generating
loop.
The
Schmitt
trigger
changes
state
at
predetermined
limits
on
the
positive
and
negative
slopes
of
the
ramp
capac-
itor
output.
The
effect
of
the
change
of
state
controls
the
switching
circuit
which
in
turn
causes
the
selec-
ted
ramp
capacitor
to
be
charged
or
discharged.
A cycle is as follows: the upper current source
charges
the
ramp
capacitor
at
a
linear
rate.
When
the
amplitude
of
the
positive
slope
of
the
ramp
reaches
the upper predetermined limit of the Schmitt trigger,
Figure 4-1.
the
trigger
circuit
changes
state.
This
change
of
state
activates
the
switching
network,
cutting
off
the
upper
current
source.
The
discharge
continues
until
the
amplitude
of
the
negative
slope
reaches
the
lower
predetermined
limit.
At
this
point
the
Schmitt
trigger
reverses
to
its
original
state,
again
activating
the
switching
circuit
and
so
completing
one
cycle.
4-6.
The
frequency
control
network,
governed
by
the
FREQUENCY
(Hz)
dial,
determines
total
current
in
both
sources
which,
in
turn,
varies
the
frequency.
An
increase
or
decrease
of
input
current,
respectively
increases
or
decreases
the
rate
of
charge
of
the
ramp
capacitor.
4-7.
Operation
of
the
SYMMETRY
control
varies
the
ratio
of
current
through
the
upper
and
lower
cur
-
rent
sources
effecting
a
change
in
the
duty
cycle,
the
frequency
remaining
constant.
4-8. The Schmitt trigger provides square waves to
both output amplifiers and for differentiation by the
trigger output circuit to produce positive and negative
triggering pulses.
6004
OUTPUT
AMPLIFIER
OUTPUT
AMPLIFIER
Basic Block Diagram.
4-1

Section IV
Paragraphs 4-9 to 4-14
4-9. SCHEMATIC THEORY.
4-10. FREQUENCY CONTROL NETWORK
4-11. The FREQUENCY dial (R2) in conjunction with
the MULTIPLIER switch (S5) provide the frequency
control. The basic frequency equation can be
expressed as: 1 1
o SCe hd
Where i, and izare currents from two current
sources, C is the ramp capacitor and e is the peak
to peak voltage of the triangular waveform across the
ramp capacitor.
The position of the MULTIPLIER switch selects the
ramp capacitor and the FREQUENCY dial determines
the sum of the currents i, and i,. The frequency
control voltage is applied to the base of current con-
trol transistor Q 11 which establishes the amount of
current available to the ramp capacitor from the
current sources @ 12 and Q 13.
4-12. CURRENT SOURCES.
Current source transistors Q 12 and Q 13 provide a
constant current for charging the ramp capacitor, the
ratio of one current to the other is divided between
the two sources by the SYMMETRY control. This
enables the charge and discharge rate of the ramp
capacitor to be controlled hence permitting the duty
cycle to be varied with no change in the frequency.
(reference Figure 4-2).
Model 211B
4-13. SWITCHING CIRCUIT.
Assume Q20 is conducting and Q21 is cut off. This
establishes a base voltage, on the switching circuit
transistors, that turns on Q14and turns off Q15. This
action creates two current paths: Current flows
through switching transistor Q14 and current source
Q12 to the -20 V supply and the ramp capacitor lin-
early discharges through CR19 and current source
Q13. As the voltage at the ramp capacitor is going
positive, the base of Q20 is going negative, until the
Schmitt trigger changes state. This reverses the
operation of the switching circuit, 14 turns off and
Q15 turns on. Current now flows through current
source Q13 and switching transistor Q15 to the -20 V
supply and current source Q12 linearly charges the
ramp capacitor through CR18. The base voltage of
@20 will go positive until the Schmitt trigger switches
again.
4-14. RAMP CAPACITOR AMPLIFIER.
On the upper four ranges the ramp capacitors C29-C32
are connected directly to ground. On the lower three
ranges C26-C28 and the ramp capacitor amplifier
form the ramp capacitor circuit. @ 16 inverts the
phase and amplifies the ramp capacitor signal present
at the emitter of 919. Q17 and Q 18 provide a low
impedance path between the ramp capacitor and ground.
The inverted ramp signal applied to the ramp capacitor
increases the charging time as shown in Figure 4-3.
[ a.
+—— PERIOD ——»
Figure 4-2. Simplified Current Source Operation.
4-2

Model
211B
Section
IV
Paragraphs
4-15
and
4-16
7° \F AMPLIFIERS NOT IN CIRCUIT
SWITCHING
LEVELS
AMPLIFIER
! OUTPUT
Figure 4-3. Ramp Capacitor Amplifier Block Diagram.
4-15. SCHMITT TRIGGER. 4-16. SYNC INPUT CIRCUIT
Four diodes, CR23-CR26, in a bridge configuration
limit the maximum amplitude of the input synchro-
The
pulse
forming
circuit
consists
of
inverter
Q
19,
nizing
signal
to
approxiamately
4
volts.
This
signal
Schmitt
trigger
©20/Q21
and
impedance
converter
activates
the
sync
pulse
generator
Q
23
and
Q
24.
LI
Q
22.
Initially
©
20
is
conducting
and
the
output
and
CR
29
generate
a
positive
spike
which
is
routed
from
@
22
is
zero.
The
ramp
capacitor
voltage
is
to
either
Q
25
and
Q
26,
depending
upon
the
duty
cycle
inverted
by
Q
19
and
the
negative
slope
passed
to
the
setting.
The
setting
is
controlled
by
S
3
which
operates
Schmitt
trigger.
At
a
predetermined
level
(set
by
in
conjunction
with
the
symmetry
control.
When
the
circuit
components)
the
Schmitt
trigger
changes
state.
duty
cycle
is
below
50%
of
the
period
Q
25
is
turned
The
output
goes
negative,
reversing
the
switching
on
and
above
50%
Q
26
is
turned
on.
(Synchronization
circuit
condition
and
the
ramp
capacitor
charges.
The
is
not
possible
exactly
at
50%
duty
cycle).
By
this
charge
continues
until
the
positive
going
slope
on
the
operation
the
sync
pulse
always
falls
on
the
long
ramp.
base
of
@
20
switches
the
Schmitt
trigger
back
to
its
When
this
occurs
the
Schmitt
trigger
@
20
and
0
21
original
state.
The
output
pulse
is
passed
to
the
changes
state
and
brings
the
repetition
rate
into
trigger
output
circuit
and
the
50Q
and
600Q
amplifiers.
synchronism
with
the
external
signal
(see
Figure
4-4).
FREE RUNNING
SYNCHRONIZED SIGNAL SCHMITT TRIGGER =
UPPER
> 50%
LOWER
FREE RUNNING SIGNAL
/
SYNCHRONIZED SIGNAL
| OUTPUT SPIKE FROM Q25
Ist OR Q26
SYNC. PULSE
Figure 4-4. Synchronizing Operation.
4-3

Section IV
Paragraphs 4-17 to 4-20
4-17. TRIGGER OUTPUT CIRCUIT.
C 33 and R 77 differentiate the square wave output of
the Schmitt trigger. Q 27 amplifies the signal and
provides the negative output trigger pulse. Q 28
inverts the polarity of the spike to provide the
positive output trigger pulse.
4-18. 6002 AMPLIFIER.
Transistors Q 43 through Q 45 and Q3/Q@4 amplifier
the Schmitt trigger square wave to provide the 600
output pulse. A negative output is taken from the
collectors of Q3/Q4 and fed through R 6 (AMPLITUDE
control) to the output connector. Diode CR 36 func-
tions as a protective device against any inductive
load.
4-19. 5082 OUTPUT
The drivers and output amplifiers Q 37 through Q 42
form the 502 output circuit. Voltage source @ 35 and
Model 211B
Q 36 regulate the base potentials of driver transistors
Q 39 and Q 42 to provide the AMPLITUDE VERNIER
control. Output attenuator A 1 provides step attenu-
ation of the negative 50Qoutput pulse.
4-20. POWER SUPPLY.
The power supply operates from either 115 or 230 V
ac which is rectified and regulated to provide dc
output of -20 V, -70 V and +6.8 V. Two seperate
primary windings of transformer T 1 are switched by
S 2, in parallel for 115 V operation or in series for
230 V operation. The -20 V and -70 V supplies operate
in a similar manner. Error amplifier transistors Q 5
or Q 8 sense and amplify any change in output voltage.
The change is applied through regulator control
transistor Q 6 and Q 7 to series regulators Q 1 and
Q 2 which act as variable series resistors in the
circuitry path. Diode CR 10 in the -70 V supply limits
the initial voltage across Q 2. The +6.8 V supply is
filtered by R 20 and C 14 and regulated by zener
diode and CR 9.

Model 211B
Section V
Paragraphs 5~1 to 5-9
SECTION V
MAINTENANCE
5-1. INTRODUCTION.
5-2. This section provides maintenance and service
information for the Model 211B Square Wave Genera-
tor. Performance check, adjustment procedures,
troubleshooting, and repair and replacement informa-
tion are the major areas covered in this section.
Component location and schematic diagrams are also
included at the rear of the section.
5-3. TEST EQUIPMENT.
5-4. Test equipment required for maintaining and
checking the performance of the Model 211B is listed
in Table 5-1. Test equipment having characteristics
similar to those listed in the table may be substituted
for the performance check and adjustments.
5-5. INSTRUMENT COVER REMOVAL.
5-6. Thetop, bottom, and side covers are seperate-
ly removable. Each cover is held in place by screws
which thread into fasteners attached to the instrument
side castings. Removal of the top cover provides ac-~-
cess to all components and test points on etched cir-
cuit boards and to nearly all other components on
front panel assemblies. Always remove instrument
PRESHOOT
\ BASELINE
PULSE WIOTH
ROUNDING
OVERSHOOT
covers with the AC power turned off or power cord
removed.
5-7. PERFORMANCE CHECK.
5-8. The performance check verifies whether or
not the Model 211B is operating within the specifica-
tions as stated in Table 1-1. This check may be used
as part of an incoming quality control inspection, as
a periodic operational check, or after repairs and /
or adjustments have been made. Recently calibrated
test equipment should be used when performing this
check. Performance checks must be carried outin the
sequence given below.
5-9. REPETITION RATE
a. Refer to Figure 5-2 and Table 5-1 and connect
required equipment
b. Set Model 211B controls as follows:
MULTIPUIER........-2++00- Ll
FREQUENCY Dial........... 1
SYMMETRY..........-5 peeve 00% duty cycle
AMPLITUDE (V across 502). .5
VERNIER. oo... cece eee e eevee d CW
OVERSHOOT
—_
ROUNDING
ae
PRESHOOT
Figure 5-1. Definition of Output Pulse Characteristics
5-1

Section V Model 211B
Table 5-1
Table 5-1. Required Test Equipment
Recommended Instrument Required
Sampling hp 185B ; Perfor mance
Oscilloscope with 187C UGH: Bandwidth Check
High Frequency hp 175A with 50 MHz Bandwidth Performance
Oscilloscope 1755A and 1781B 50 mV/cm Sensitivity Check
10:1 Divider hp 10214A 1 GHz Bandwidth Performance
Check
: Performance
hp 410221A 1 GHz Bandwidth Chask
Weinschel Use Recommended Performance
Model 50-20-S Equipment Check
Perfor mance
Check
pom | |e
meats | Ba
Test
Oscillator
:
Ee
ae
ee
|
eee
oe
=
5-2

Model 211B
50N LOAD
2B
TRIG. 500
101204
lOl20A
Figure 5-2. Dial Accuracy Check
c. Set Electronic Counter controls as follows:
SIGNAL INPUT...........+-- AC
SENSITIVITY. .......022e5 00s 0.1 V
TIME BASE ........ de tile esbeereee O.1y sec.
FUNCTION,.......22e eevee 1 Period Average
d. Electronic Counter should read 1 000 000s
+50 000us
e, Set FREQUENCY Dial to 5, Electronic Counter
should read 200 000us +10 000us
f. Set FREQUENCY Dial to 10, Electronic Counter
should read 100 000us +5 000us
g. Set MULTIPLIER to 10 and FREQUENCY Dial
to 1, Electronic Counter should read 100 000us
+5 000us
h. Repeat steps e and f with MULTIPLIER at
10,Electronic Counter should read 20 000ps +1000us
and 10 000us ¢500us respectively.
i. Set MULTIPLIER to 100 and FREQUENCY Dial
to 1, Electronic Counter should read 10 000us +500ys
j. Repeat steps e and f with MULTIPLIER at
100, Electronic Counter should read 2 000us +100us
+5008 respectively.
k. Set Electronic Counter FUNCTION to
FREQUENCY and TIMEBASE to 1 sec.
1, Complete check by setting Square Wave Gen-
erator MULTIPLIER switch and FREQUENCY Dial
as shown in Table 5-2 columns one and two. The
Electronic Counter reading should be as shown in
column three.
Section V
Paragraphs 5-10 to 5-12
Table 5-2. Dial Accuracy
ULTIPLIER|FREQUENCY COUNTER
DIAL READING
1000Hz
5000Hz
10KHz
10KHz
50KHz
+50Hz
+250Hz
+500Hz
+500Hz
+2. 5KHz
t5KHz
t5KHz
+25KHz
+50KHz
t50KHz
+250KHz
t500KHz
100KHz
100KHz
500KHz
1000KHz
1000KHz
5000KHz
10000KHz
5-10. SYMMETRY CONTROL CHECK
a. With Model 211B connected as shown in
Figure 5-2, set the controls as follows:
MULTIPLIER............665 10K
FREQUENCY Dial............ 1
SYMMETRY ...........0000% CW
AMPLITUDE (v across 502). . 5
VERNIER.......--.cc eee eees CW
TIME SCALE..........00085 20us/cm
TIME SCALE MAGNIFIER... .X1
TRIGGER SOURCE........... internal
SWEEP SELECTOR.......... main sweep
CHANNEL SELECTOR...... . channel A
SENSITIVITY.............. 2 V/cm de coupled
POLARITY...........00.005 positive
c. Adjust oscilloscope for a stable display
d. The "on time" should be greater than 75% of
the period.
e. Turn the SYMMETRY control CCW and the
"on time"should be less than 25% of the period.
5-11. OUTPUT PULSE CHARACTERISTICS.
5-12. Refer to Figure 5-1 for definition of pulse
characteristics. Follow these procedures in sequence
since each paragraph continues the same equipment
connections and front panel settings as in the pro-
ceeding paragraph. Any required changes in control
settings are specified in the procedures. All mea-
surements are made with a 10:1 divider.
5-3

Section V
Paragraph 5-13 to 5-17
GR874 -W50
410221A
50Q TEE
2118
TRIG. SOQ
Figure 5-3. 50 Output Pulse Check
5-13. 502 OUTPUT
5-14. Pulse Amplitude
a. Refer to Figure 5-3 and connect required equip-
ment.
b. Set Model 211B controls as follows:
MULTIPLIER............... 1M
FREQUENCY DIAL......... 1
SYMMETRY..........0c cee 50% duty cycle
AMPLITUDE (v across 502). .5
VERNIER........cceseeeceee CCW
TRIGGER POLARITY........ negative
c. Set Sampling Oscilloscope controls and plug-in
as follows:
TIME SCALE........-000006 200ns/cm
VERNIER,.... ccc ececceees CAL
TIME SCALE MAGNIFIER... X1
TRIGGERING. ........002 eee normal
TRIGGER SLOPE........... negative
MODE AND STABILITY...... for stable trace
CHANNEL SELECTOR....... channel A
SENSITIVITY. .........0..00- 50mV/cm
VERNIER..........eeceee CAL
RESPONSE........eccceceee normal
d. The oscilloscope display should be no more
than 4 cm (2 V)in amplitude. ]}f 4 cm or less is
observed the ratio between CW and CCW is at least
2.5 to 1. Therefore at a 0.05 V pulse amplitude
setting the minimum of 0.025 V output can be
obtained.
5-15. Pulse shape
a. Set Oscilloscope TIME SCALE to 20ns/cm.
b. Set Model 211B FREQUENCY dial to 5, set
AMPLITUDE (V across 502) switch to 5 and adjust
VERNIER for a pulse amplitude of 5 V (10cm).
c. Change the time scale MAGNIFIER to X20.
Move the leading edge of the pulse to the center of the
graticule,
5-4
Model 211B
f. The following leading edge characteristics
should be observed.
Rise Time 10% to 90%. .. No more than 5 cm (5ns)
Preshoot.............. No more than 5 mm (5%)
Overshoot and Ringing. . No more than 5 mm peak
(5%)
g. Adjust Oscilloscope DELAY control for display
of pulse trailing edge.
h. The following trailing edge characteristics
should be observed
Fall Time 10% to 90%...Nomore than 5 ¢m (5ns)
Preshoot.............. No more than 5 mm (5%)
Overshoot and Ringing.. No more than 5mm peak
; (5%)
5-16. 6002 OUTPUT
5-17. Pulse Amplitude
a. Refer to Figure 5-4 and connect required equip-
ment.
b. Set Model 211B controls as follows:
MULTIPLIER..........-+445 10K
FREQUENCY DIAL.......... 10
SYMMETRY.............26- 50% duty cycle
AMPLITUDE - 6002......... CW
c. Set High Frequency Oscilloscope and plug-in’ s
as follows:
SWEEP TIME.............4- 2us/em
VERNIER........0cceeeee CAL
HORIZONTAL DISPLAY...... X1
VERNIER.......0000ceeees CAL
TRIGGER SOURCE.......... internal
TRIGGER SLOPE........... negative
CHANNEL SELECTOR....... channel A
SENSITIVITY. ...........006. 1 V/em - de
VERNIER.........2000000. CAL
POLARITY.............000- positive
SWEEP SELECTOR......... main
10003 B
Figure 5-4. 6002 Output Pulse Check

Model 211B
d.
Adjust
AMPLITUDE
control
for
a
pulse
ampli-
tude
of
60
V
(6cm).
The
overshoot
should
be
less
than
3
mm
(5%).
e.
Connect
a
6002
load
across
the
output.
The
pulse
amplitude
should
be
at
least
30
V
(3cm).
f. Set Oscilloscope plug-in SENSITIVITY to
0.01
V/em
and
adjust
AMPLITUDE
control
for
0.3
V
(3cm).
The
overshoot
should
be
less
than
3
mm
(5%).
5-18. Rise and Fall Times
a.
Set
the
Oscilloscope
SWEEP
TIME
to
0.
2us/cem
and
SENSITIVITY
to
1V/em.
b.
Move
the
leading
edge
of
the
pulse
to
the
center
of
the
CRT.
Set
HORIZONTAL
DISPLAY
to
X10.Check
rise
time
between
10%
and
90%
amplitude
points.
It
should
be
less
than
7
cm
(140ns).
c.
Change
the
Oscilloscope
TRIGGER
SLOPE
to
positive
and
move
the
trailing
edge
of
the
pulse
to
the
center
of
the
CRT.
Check
fall
time
between
the
10%
and
90%
amplitude
points.
It
should
be
less
than
7
cm
(140ns).
d. Connect the Model 211B output to a 600 load.
e. Set the Oscilloscope plug-in SENSITIVITY to
0.5
V.
Check
the
fall
time
between
10%
and
90%
amplitude
points.
It
should
be
less
than
3.5
cm
(70ns)
f. Change the Oscilloscope TRIGGER SLOPE to
negative
and
move
the
leading
edge
of
the
pulse
to
the
center
of
the
CRT.
Check
rise
time
between
10%
and
90%
amplitude
points.
It
should
be
less
than
3.5
cm
(70ns). Remove the 6002 load.
5-19. SYNCHRONIZATION
5-20.
This
procedure
will
verify
that
the
Model
211B
is
capable
of
synchronizing
with
an
external
trigger
input
of
at
least
1
V
peak
or
2
V
rms
at
frequencies
slightly
higher
than
the
set
repetition
rate.
a.
Refer
to
Figure
5-5
and
connect
required
equip-
ment.
50 O LOAD
28
sync. 500
50a 6000
651A
Figure 5-5. External Pulse Synchronization
Section V
Paragraphs 5-18 to 5-22
b. Set Model 211B controls as follows:
MULTIPLIER..........--06- 1K
FREQUENCY DIAL.......... 10
SYMMETRY..........000088 CCW
AMPLITUDE ( across 502)..5V
VERNIER......-- cece eee ceee CW
c.
Set
Oscilloscope
and
plug-in
controls
as
follows:
SWEEP
TIME.........---065
5us/cem
HORIZONTAL
DISPLAY......
X1
VERNIER.......0e
eee
eceee
CAL
TRIGGER
SOURCE..........
external
SWEEP
SELECTOR........
.
main
sweep
CHANNEL
SELECTOR......
channel
A
SENSITIVITY.
......-000000:
2V/em
de
VERNIER........e0
ee
eeeee
CAL
RANGE ois oc 6ce eo adie aie 8 are serereues X10K
FREQUENCY DIAL.......... 1,1
OUTPUT ATTENUATOR..... 3 V
AMPLITUDE
502...........
2
V
pk
to
pk
e,
Adjust
Oscilloscope
sweep
time
VERNIER
for
a
full
graticule
period
(10cm).
f. Turn 651A FREQUENCY Dial slowly CCW until
a half graticule period (5cm) is obtained.
g. Turn the Model 211B SYMMETRY control slowly
CW and observe the 180° phase shift at 50% duty cycle.
5-21. TRIGGER OUTPUT
5-22. This procedure verifies the Trigger Output
characteristics
of
the
Model
211B.
Refer
Figure
5-6
for connection.
a. Set Model 211B controls as follows:
MULTIPLIER.............-- 1M
FREQUENCY DIAL.......... 5
AMPLITUDE (5v across 50%). 5
VERNIER......c. ccc cenccas CW
TRIGGER POLARITY........ negative
GR874 -W50
4102214
500 TEE
28
TRIG. 500
Figure 5-6. Trigger Output Pulse Check
5-5

Section V
Paragraphs 5-23 to 5-35
b. Set Sampling Oscilloscope controls as follows:
TIME SCALE............... 20ns/cm
VERNIER.........020ceeee CAL ‘
TIME SCALE MAGNIFIER... .X2
CHANNEL SELECTOR....... Channel A
SENSITIVITY............026 50mV/em
c. Move the trigger pulse to the center of the CRT.
The pulse amplitude should be 2 V or more.
d. Adjust Oscilloscope plug-in sensitivity VERNIER
for a full screen picture. Observe the pulse width at
50% amplitude points. The pulse width should be 10ns
(1 cm).
e. Change Model 211B TRIGGER POLARITY switch
to positive. Pulse should be positive and same speci-
fications asin steps c and d apply.
5-23. POWER SUPPLY
5-24. If the power supply circuits are inoperative,
check the power cord connection and line fuse F 1.
Refer to the schematic for other components in the
ac portion of the power supply circuit. All dc voltage
measurements, typical values indicated on the sche-
matic, should be made with respect to chassis ground.
Adjustments can be made after the top cover of the
211B has been removed.
a. Adjust R18 for -20 V
b. Adjust R26 for -70 V
5-25. TROUBLESHOOTING
5-26. To locate trouble in the 211B, start with a
thorough visual inspection and then proceed to
electrically check out as necessary. During the visual
inspection look for burned or loose components, loose
wire connections, or any other similar condition
which suggests a source of trouble. Repair any faulty
component or connection that is isolated during the
visual inspection and check instrument performance
before continuing to troubleshoot the instrument.
5-27. If no obvious fault is located during the visual
inspection proceed with the electrical check out. Use
the block diagrams in Section IV as an aid in isolating
the trouble to a particular circuit.
5-28. REPAIR AND REPLACEMENT
5-29 Repair of the Model 211B consists basically of
replacing defective components located during trouble-
5-6
Model 211B
shooting. The following paragraphs provide informa-
tion on the identification and location of all components
in the Model 211B, and basic considerations when
repairing etched circuit boards. If satisfactory
operation or repair cannot be accomplished, contact
your nearest Hewlett-Packard Sales/Service Office
(adresses given at rear of this manual). If shipment
of the instrument to the Sales/Service Office for
repair is recommended, refer to Paragraph 2-4 for
repackaging information. Refer to Section VI for part
numbers of replaceable parts and ordering instructions.
5-30. COMPONENT IDENTIFICATION.
5-31. All electrical components in the Model 211B
are identified on the schematics with a reference
designation. Location of components mounted on etched
circuit boards or switches is provided in the compo-
nent location figures. All electrical components not
mounted on etched circuit boards or switches are
identified in Figure 5-10.
5-32. To help with proper replacement of semicon-
ductors, the emitter or cathode connection is
identified by a small dot etched on the circuit board
beside the connection point.
5-33. SERVICING ETCHED CIRCUIT BOARDS.
5-34, The Model 211B has etched circuit boards
which are plated-through type. When servicing this
type of board, components may be removed or
replaced by unsoldering from either side of the board.
When removing large components, such as potentio-
meters, rotate the soldering iron tip from lead to
lead while applying pressure to the part to lift it from
the board. Service Note M-20D contains additional
infirmation on the repair of etched circuit boards,
however, the important considerations are as follows:
a. Do not apply excessive heat.
b. Apply heat to component lead and remove lead
with a straight pull away from board.
c. Use toothpicker or wooden splinter to clean hole.
‘d. Do not force leads of replacement component
into holes.
5-35. If the plated metal surface (conductor) lifts
from the board, it may be cemented back with a quick-
drying acetate base cement (use sparingly) having
good insulating properties. An alternate method of
repair is to solder a good conducting wire along the
damaged area.