Tektronix TEK 222 User manual

T
E-
SERVICE
063-0066-00
7
MANUAL
Product
Group
40
222
Digital
Storage
Oscilloscope
Preliminary
Service
THE FOLLOWING SERVICING INSTRUCTIONS ARE
FOR USE BY QUALIFIED PERSONNEL ONLY. TO
AVOID
PERSONAL
INJURY,
DO
NOT
PERFORM
ANY
SERVICING
OTHER
THAN
THAT
CONTAINED
IN
OPERATING
INSTRUCTIONS
UNLESS
YOU
ARE
QUALIFIED
TO
DO
SO.
REFER
TO
OPERATORS
SAFETY
SUMMARY
AND
SERVICE
SAFETY
SUMMARY
PRIOR
TO
PERFORMING
ANY
SERVICE.
First Printing April 1989
Tektronix.
COMMITTED TO EXCELLENCE

Copyright
©
1989
Tektronix,
Inc.
All
rights
reserved.
Contents
of
this
publi-
cation
may
not
be
reproduced
in
any
form
without
the
written
permission
of
Tektronix,
Inc.
Products
of
Tektronix,
Inc.
and
its
subsidiaries
are
covered
by
U.S.
and
foreign
patents
issued
and
pending.
TEKTRONIX,
TEK,
SCOPE-MOBILE,
and
ane
are
registered
trademarks
of
Tektronix,
Inc.
Printed
in
U.S.A.
Specification
and
price
change
privileges
are
reserved.

LIST OF ILLUSTRATIONS
LIST OF TABLES
OPERATORS
SAFETY
SUMMARY
SERVICING
SAFETY
SUMMARY
222
DSO
Preliminary
Service
TABLE
OF
CONTENTS
SECTION
1
SPECIFICATIONS
INTRODUCTION
.............
RECOMMENDED
PERFORMANCE CHECK
SCHEDULE
.................
ELECTRICAL
SPECIFICATIONS
............
VERTICAL DEFLECTION
SYSTEM
..............0.0.
ENVIRONMENTAL
SPECIFICATIONS
............
MECHANICAL
SPECIFICATIONS
............
BATTERY-CHARGER
ADAPTER
5
vias
inn
nscensegen
EXTERNAL SUPPLY
VOLTAGE
...................
FIRST TIME BATTERY
OPERATION
.................
START-UP
.................,
VIEWING
A
SIGNAL
QUICKLY
..
Page
TIPS
ON
BATTERY
CARE
......
2-2
BATTERY
REPLACEMENT......
2-3
SECTION
3
BLOCK
DIAGRAM
OVERVIEW
INTRODUCTION
.............
3-1
ACQUISITION
SYSTEM
........
3-1
TIME
BASE
..................
3-4
PROCESSOR
SYSTEM
........
3-4
DISPLAY
SYSTEM
............
3-6
BATTERY CHARGER
RECTIFIER
.................,
3-9
POWER
SUPPLY
............
3-10
SECTION
4
PERFORMANCE
CHECK
PROCEDURE
INTRODUCTION
.............
4-1
TEST EQUIPMENT
REQUIRED
..................
4-1
PERFORMANCE
CONDITIONS
................
4-1
PERFORMANCE
CHECK
INTERVAL
.............0.000.
4-1
PREPARATION
...............
4-1
INDEX
TO
PERFORMANCE
CHECK
PROCEDURE
.........
4-5
DISPLAY
CHECKS
..............
4-6
INITIAL
CONTROL
SETTINGS
...
4-6
PROCEDURE
................
4-6
VERTICAL
...............0000
0,
4-7
INITIAL
CONTROL
SETTINGS
...
4-7
PROCEDURE
................
4-7
HORIZONTAL
..................
4-11
INITIAL
CONTROL
SETTINGS
..
4-11
PROCEDURE
...............
4-11
TRIGGER
................000,
4-12
INITIAL CONTROL
SETTINGS
................,
4-12
PROCEDURE
...............
4-12

222 DSO Preliminary Service
Page
SECTION 5 ADJUSTMENT PROCEDURE
INTRODUCTION ............. 5-1
TEST EQUIPMENT
REQUIRED ...........000005. 5-1
LIMITS AND TOLERANCES ..... 5-1
ADJUSTMENTS AFFECTED BY
CIRCUIT BOARD
REPLACEMENT ............-- 5-1
PREPARATION FOR
ADJUSTMENT ...........-05. 5-1
PROCEDURE STEPS ............. 5-2
PREPARATION .............-. 5-2
ADJUSTMENTS ............5. 5-2
SECTION 6 MAINTENANCE
STATIC-SENSITIVE
COMPONENTS .............055 6-1
PREVENTIVE MAINTENANCE ..... 6-3
INTRODUCTION ............. 6-3
INSPECTION AND CLEANING .. 6-3
LUBRICATION .............5. 6-5
PERIODIC READJUSTMENT .... 6-5
TROUBLESHOOTING ........... 6-6
INTRODUCTION ............. 6-7
TROUBLESHOOTING AIDS .... 6-7
TROUBLESHOOTING
TECHNIQUES ............... 6-7
CORRECTIVE MAINTENANCE .... 6-8
INTRODUCTION ............. 6-8
MAINTENANCE
PRECAUTIONS .............. 6-8
REPACKAGING FOR
SHIPMENT ...........0.0000. 6-8
REMOVE AND REPLACE
PROCEDURES ................. 6-9
TOP CASE REMOVAL ......... 6-9
Page
PROBE REMOVAL AND
REPLACEMENT ............-- 6-9
FRONT PANEL SWITCH BOARD
REMOVAL ..........00000005 6-11
TOP PANEL SWITCH BOARD
REMOVAL.........000000005 6-11
POT BOARD REMOVAL ...... 6-11
CRT REMOVAL ............. 6-11
POWER SUPPLY BOARD
REMOVAL............0-000: 6-12
CPU/DISPLAY BOARD
REMOVAL.........000000005 6-12
ACQUISITION BOARD AND
MAIN BOARD REMOVAL ..... 6-12
ACQUISITION BOARD
REPLACEMENT ............. 6-12
ACQUISITION BOARD AND
MAIN BOARD
REINSTALLATION ........... 6-12
CPU/DISPLAY BOARD
REINSTALLATION ........... 6-12
POWER SUPPLY BOARD
REINSTALLATION ........... 6-12
CRT REINSTALLATION ....... 6-12
POT BOARD
REINSTALLATION ........... 6-12
CASE REASSEMBLY ......... 6-12
SECTION 7 OPTIONS AND ACCESSORIES
INTRODUCTION ............. 7-1
STANDARD ACCESSORIES .... 7-1
OPTIONAL ACCESSORIES ..... 7
OPTIONS .............00 00s. 74
FIELD ACCESSORY KIT
PARTS LIST .............0005 7-1
SECTION 8— REPLACEABLE PARTS

222 DSO Preliminary Service
LIST OF ILLUSTRATIONS
Figure
Page
1-1
Maximum
ac
common-mode
voltage
versus
frequency
derating
curve..............
1-5
2-1
External
Power
Input
....
0.2...
ccc
cece
cence
e
eee
eeeeeneennenes
2-1
3-1
Simplified
block
diagram
of
the
222
DSO
..........
0.
cc
ccc
ccc
eee
eee
eeees
3-2
3-2
Floating
Acquisition
System
1.2.0.0...
ccc
cece
cc
cece
eee
ee
neeeeeeunees
3-3
3-3
Processor
System
simplified
block
diagram
...........
0...
cece
eee
ccc
e
eee
eees
3-5
3-4
Display
System...
...
0.
ccc
cece
eee
cece
cece
eeennaannnnns
3-7
3-5
Battery
Charger
block
diagram
.............
cece
ccc
cece
cece
eee
eeeeeauneeeus
3-9
3-6
Power
Supply
block
diagraM
.............
cc
cece cece
eee
eee
eeneeeeeunnees
3-10
4-1
RS-232
interconnection
cable
wiring
...........
0.00
ccc
cece
eee
n
ence
eeuenes
4-4
4-2
Trigger
Jitter
CHECK...
1...
ccc
cece
cence
eee
e
eens
enetennenns
4-14
5-1
Rear
Panel
adjustments
........
0...
cece
ccc
ce
cee
cee
eeeneenenneens
5-3
5-2
Top
accessible
adjustments
.......
0...
0.
ccc
cee
cc
cece
eee
ence
eneeeneeenns
5-4
5-3
CH1
and
CH2
Input
Compensation
..............
0.
ccc
cece
cee
e
eee
e
cence
5-5
5-4
Clock
Delay
adjustment
............
cece
cece
eee
cece
eee
eceaceneeeedaes
5-6
6-1
Circuit
board
locations
........
0...
cece
cee
cece
cece
eeennnneunees
6-10
Table
Page
4-1
Test
Equipment
Required
.........
0...
cece
ce
cece
ene
e
ee
nnneeeeeennns
4-2
4-2
VOLTS/DIV
Accuracy
Settings
............
0...
ccc
ccc
ec
c
ence
unnns
4-9
6-1
Relative
Susceptibility
to
Static-Discharge
Damage
................
ccc
cece
eee
eee
6-1
6-2
External
Inspection
Checklist
.............
ccc
cece
eee
cece
cece
eeeeeeeenns
6-3
6-3
Internal
Inspection
Checklist
...........
00.
e
cece
eee
eeeeeeeuneues
6-4

222 DSO Preliminary Service
OPERATORS SAFETY SUMMARY
The
safety
information
in
this
summary
is
for
operating
personnel.
Warnings
and
cautions
will
also
be
found
through-
out the manual where they apply.
Terms in this Manual
CAUTION statements identify conditions or practices
that could result in damage to the equipment or other
property.
WARNING statements identify conditions or practices
that could result in personal injury or loss of life.
Terms as Marked on Equipment
CAUTION indicates a personal injury hazard not
immediately accessible as one reads the markings, ora
hazard to property, including the equipment itself.
DANGER indicates a personal injury hazard im-
mediately accessible as one reads the marking.
Symbols in this Manual
A Indicates where applicable cautionary or
other information is to be found. For
maximum input voltage ratings, see
the Specifications.
SERVICING SAFETY SUMMARY
FOR QUALIFIED SERVICE PERSONNEL ONLY
Refer
also
to
the
preceding
Operators
Safety
Summary
Do Not Service Alone
Do not perform internal service or adjustment of this
product unless another person capable of rendering first
aid and resuscitation is present.
Use Care When Servicing With Power On
Dangerous voltages exist at several points in this
product. To avoid personal injury, do not touch exposed
connections or components while power is on.
Iv
Disconnect power and remove the battery before
removing
protective
panels,
soldering,
or
replacing
components.

Section 1—222 DSO Preliminary Service
SPECIFICATIONS
INTRODUCTION
Performance characteristics given in the Electrical
Specifications apply when the instrument has been self
calibrated within + 5°C of the ambient temperature, has
warmed up at least 20 minutes, and is operating in an
ambient temperature between -10°C and +55°C
(unless otherwise noted).
Items listed in the Detailed Specifications are verifiable
limits that define the measurement capabilities of the
instrument.
Environmental Specifications are given and Mechanical
Specifications are given following the Electrical
Specifications.
RECOMMENDED PERFORMANCE
CHECK SCHEDULE
To ensure accurate measurements, check the per-
formance of this instrument every 2000 hours of
operation (once each year if used infrequently). If repairs
are made, affected circuits may need to be readjusted.
ELECTRICAL SPECIFICATIONS
VERTICAL DEFLECTION SYSTEM
Deflection Factor
5 mV per division to 50 V per division in a 1-2-5
sequence.!
Vertical Resolution
8-bits, 25 levels per division. 10.24 divisions of
dynamic range.'
DC Accuracy
-10°C to +55°C +3% (when the self
calibration has been
done within + 5°C of the
ambient temperature).
1Performance Requirement not checked in manual.
VOLTS/DIV Variable Control
Increases the deflection factor by 2.5 to 1.
Aberrations
+6%, -6%. 6% p-p or less.1
Measured with a 5-division reference signal, from a
50-2 source driving a 50-0 load at the probe tip.
Vertically center the top of the reference signal.
Useful Rise Time
SEC/DIVx 1.6 1
50
Rise time is limited to 35 ns by the vertical amplifier
response.
Useful Bandwidth
—S 71
SAMPLE
Timebase
put
Useful-storage bandwidth is limited to the
frequency where there are 10 samples per sine-
wave signal period at the maximum sampling rate.
This yields a maximum amplitude error of 5%. Maxi-
mum sampling rate is 10 MHz at 5 ys per division.
Accuracy at the useful-storage-bandwiath limit is
measured with respect to a 6-division, 50-kHz sine
wave.
REPETITIVE
0.5 ys/div to 50 ys/div 10 MHz.
1 ys/div 5 MHz.!
2 us/div 2.5 MHz.!
Bandwidth is limited to 10 MHz by the analog
system.
PEAK DETECT (ENV and CONT ENV acauisition
modes at 20 ps per division and slower)
Sine-wave Amplitude Capture
(5% p-p maximum amplitude
uncertainty) 1 MHz.
1-1

Specifications — 222 DSO Preliminary Service
Pulse Width Amplitude Capture
(50% p-p maximum amplitude
uncertainty). 100 ns.
A/D Converter Linearity
Monotonic with no missing codes.'
Position Control Range
+ 12 divisions.
Input Linear Range
+20 divisions.
DC Balance
0.2 division or less trace shift when switching
between VOLTS/DIV switch settings when the
ambient temperature is within +5°C of the tem-
perature at which the last self calibration was done.
INVERT Balance
0.4 division or less trace shift when switching
between INVERT and non-INVERT displays when
the ambient temperature is within + 5°C of the tem-
perature at which the last self calibration was done.
Input Current
2.5 nA or less (0.5 division or less trace shift when
switching between DC and GND input coupling with
the
VOLTS/DIV
switch
at
5
mV
per
division)".
Input R and C
Input
Resistance
1MQ
+10%.!1
Input
Capacitance
27
pF
+3
pF.!
These
R
and
C
characteristics
include
the
probe.
A Maximum Rated Input Voltage
400
V
(dc
+
peak
ac)
or
800
Vac
p-p
at
1
kHz
or
less.1
'Performance
Requirement
not
checked
in
manual.
1-2
See Figure 1-1 for voltage versus frequency
derating curve.
A Maximum Common-Mode Potential
400 V (dc + peak ac).!
A Maximum Common-Mode Ac Potential
DC-to-1 kHz 800 V peak-to-peak.!
1 kHz-to-100 kHz See Figure 1-1 for
voltage versus
frequency derating
curve.
A Maximum Potential Between Channels
800 V (dc + peak ac).!
Common-to-Ground Capacitance
Less than 150 pF.’
Common-Mode Rejection Ratio
DC-to-1 kHz 80 dB or more.1
1 kHz-to-100 kHz 60 dB or more.!
Isolation:
Channel
Signal
to
Channel
Signal
DC-to-10 MHz 80 GB or more.!
Isolation:
Channel
Common
to
Channel
Common
DC-to-1 kHz 80 dB or more.!
1
kHz-to-100
kHz
60
dB
or
more.!
TRIGGER SYSTEM
Internal
Sensitivity
0.5
division
to
20
MHz.
Level
+20
divisions.

External
Sensitivity
200
mV
to
10
MHz.
Level t2.3V.
Input
Resistance
1MQ
+10%.!1
Input
Capacitance
18
pF
+5
pF.!
Trigger Jitter
2 1 S/div to 50 ns/div (5 ns/div in X10 MAG)
x1 1/50th division +2 ns.1
X10 MAG 1/Sth division +2 ns.
HORIZONTAL SYSTEM
Range
50 ns per division to 20 s per division.'
The X10 MAG control extends the maximum sweep
speed to 5 ns per division.
Displayed Accuracy
x1 t2%.
X10 MAG +5%.1
Accuracy is over 10 divisions.
Sample Rate
NORMAL SEC/DIV ~~
PEAKDET (ENV and
CONT ENV) 10 MHz.!
REPETITIVE
50 ns/div to 1 ws/div 10 MHz.1
2 ps/div 5 MHz.1
ACCURACY 0.01%.
Sample
accuracy
is
based
on
the
accuracy
of
the
20-MHz
oscillator.
'1Performance
Requirement
not
checked
in
manual.
Specifications
—
222
DSO
Preliminary
Service
Record Length
512
data
points;
calibrated
to
50
points
per
division’.
POSITION Control Range
Start
of
the
first
division
and
end
of
the
tenth
division
can
be
positioned
past
the
center
vertical
graticule.
Displayed Trace Length
10.24 divisions.1
X-Y OPERATION
Accuracy
Same as the Vertical system.1
Useful Bandwidth
5
SEC/DIV
Hz.1
Skew Between CH 1 and CH 2
5 ns.1
RS-232 INTERFACE
Maximum
Applied Voltage
(any
pin)
25 V (dc + peak ac).1
Baud Rates
300,
1200,
2400,
9600;
0.1%
accuracy
based
on
the
microprocessor
clock.1
Signals
RD,
TD,
and
SGND.
SGND
is
connected
internally
to
EXTERNAL
TRIG
COM.
DSR
and
CTS
are
always
high,
and
DTR
and
RTS
are
ignored.1
Levels
Compatible with RS-232C.
1-3

Specifications — 222 DSO Preliminary Service
EXTERNAL POWER REQUIREMENTS
Voltage Range
Pin-to-pin
AC 16.0 to 20 Vac
at 47 to 400 Hz.!1
DC 12 to 28 Vdc.!
Either Power Pin-to-EXT
TRIG COMM or RS-232
COMM -0.5 V to 42 Vac
peak.!
Current
1 ampere maximum when charging batteries.1
Maximum Power Consumption
15 watts or 16 volt-amperes (when charging
batteries).1
INTERNAL BATTERIES
Battery
Sealed, lead-acid battery."
Charge Time
Three hours for full charge with oscilloscope not
operating."
Battery Excessive Discharge Protection
Instrument operation is automatically interrupted
when battery charge drops to 7.32 V.1
Typical Operating Time
Two hours at maximum sample rate, no trigger, and
auto shutdown defeated.
'Performance Requirement not checked in manual.
1-4
Battery Capacity versus Temperature
-15°C 20°C to 30°C 55°C
* 80% 100% 110%
ENVIRONMENTAL SPECIFICATIONS
Environmental Requirements
Instrument will meet the requirements of
Tektronix Standard 062-2853-00, Class 3.
The instruments meets all the following
MIL-T-28000D requirements for Type Ill, Class
3 equipment, except where noted otherwise.
Temperature
Operating -10°C to +55°C
(+ 14°F to +131°F).1
Nonoperating -51°C to +71°C
(-60°F to + 160°F).1
Tested
to
MIL-T-28800D,
para
4.5.5.1.3
and
4.5.5.1.4
except
that
in
para
4.5.5.1.3,
steps
4
and5
are
performed
before
step
2
(-51°C
nonoperating
test).
Equipment
shall
remain
off
upon
return
to
room-ambient
temperature
during
step
6.
Exces-
sive
condensation
shall
be
removed
before
operat-
ing
during
step
7.1
Altitude
4,570 meters (15,000
feet). Maximum
operating temperature
decreases 1°C per
1,000 feet above
5,000 feet.1
Operating
Nonoperating To 15,240 meters
(50,000 feet).1

Humidity (Operating and Nonoperating)
Five cycles (120 hours) referenced to
MIL-T-28800D para 4.5.5.1.2 for type Ill, Class
3 instruments. Operating and nonoperating at
95% (-5%, +0%) relative humidity. Operating
at +30°C and +55°C for all modes of
operation;
nonoperating
at
+30°C
and
+60°C.!1
EMI
Meets
radiated
and
conducted
emission
requirements
per
VDE
0871,
Class
B.
Meets
FCC
section
15,
sub-part
J,
Class
A.1
To
meet
EMI
regulations
and
specifications,
use
the
specified
shielded
cable
and
metal
con-
nector
housing
with
the
housing
grounded
to
the
cable
shield
on
the
RS-232
connector.
Vibration (operating)
15 minutes along each of 3 major axes at a total
displacement
of
0.025
inch
p-p
(3.8
g
at
55
Hz)
with
frequency
varied
from
10
Hz
to
55
Hz
in
1-minute
sweeps.
Hold
for
10
minutes
at
55
Hz
in
each
of
the
three
major
axes.
All
major
resonances must be above 55 Hz.1
Shock
(Operating
and
Nonoperating)
50 g, half-sine, 1-ms duration, 3 shocks per
axis
each
direction,
for
a
total
of
18
shocks.1
Specifications
—
222
DSO
Preliminary
Service
MECHANICAL
SPECIFICATIONS
Weight
Without
accessories
4.4
Ibs
(2
kg).
With
accessories
6
Ibs.
Domestic
Shipping
Weight
7
Ibs.
Dimensions
Length
9.9
in
(252
mm).
Height
3.4
in
(86.4
mm).
Width
6.25
in
(158.8
mm).
Cooling
There
are
no
cooling
vents
provided.
Finish
Tektronix
Blue
pebble
finish
with
black
synthetic
rubber
hand
grips
and
black
vinyl
probe
pouch.
Construction
Plastic
cabinet.
Glass-laminate
circuit
boards
with
surface-mounted components.
CRT
CRT
graticule
area
is
8
divisions
high
by
10
divisions
wide.
The
divisions
are
0.5
cm
on
a
side
and
the
di-
agonal
size
is
6.4
cm
(approximately
2.5
inches).
A
special
low-reflectance
surface
on
the
crt
face
aids
viewing
in
high-ambient
light
areas.
800
a
<
tas
Qa
oOo
= 80
PY 4
<x
tel
a.
wn
"i 8
Qo
>
0.8
100
Hz
1
kHz
10
kHz
100 kHz
Figure
1-1.
Maximum
ac
common-mode
voltage
versus
frequency
derating
curve.

Section 2—222 DSO Preliminary Service
OPERATING
INFORMATION
SAFETY
Refer
to
the
Operator’s
and
Servicing
Safety
Summaries
at
the
front
of
this
manual
for
safety
information
about
the
use
of
this
instrument.
Before
connecting
the
instrument
to
a
power
source,
read
this
section
and
both
Safety
Summaries.
BATTERY-CHARGER ADAPTER
Instruments
are
shipped
with
a
detachable
battery-
charger
adapter
(wall
transformer)
that
plugs
into
an
ac
power-source
outlet.
The
adapter
converts
the
power-
source
ac
voltage
to
the
16
to
20
Vac
input
voltage
needed
to
operate
the
instrument
(with
or
without
the
battery
installed)
and
charge
the
oscilloscope’s
internal
battery.
Use
the
battery-charger
adapter
to
operate
the
oscilloscope
when
an
ac
line
voltage
source
is
available
to
maintain
battery
charge
for
use
when
totally
portable
operation
of
the
oscilloscope
is
needed.
Use
the
appropriate
battery
charger adapter
for
the
available
power
source
voltage
(115
Vac
and
230
Vac).
The
adapter
plugs
into
the
instrument’s
external
power
receptacle
as
shown
in
Figure
2-1.
EXTERNAL SUPPLY VOLTAGE
The
222
operates
on
an
external
supply
voltage
of
either
12
to
28
Vdc
or
16
to
20
Vac
(47
to
400
Hz)
from
a
supply
that
provides
at
least
15
watts
or
16
volt-amperes.
Ifthe
battery
charge
state
is
very
low,
the
current
drawn
by
a
charging
battery
from
the
supplied
battery-charger
adapter
(wall
transformer)
is
current
limited,
and
the
crt
display
may
not
be
stable.
If
this
effect
is
seen,
either
charge
the
battery
for
1
hour
before
operating
the
oscillo-
scope
or
operate
without
the
battery
installed
until
it
can
be
charged.
BATTERY OPERATION
The
internal
battery
of
the
instrument
is
a
sealed
lead-
acid
type
with
four
cells.
The
sealed
cells
are
re-
chargeable
using
the
battery-charger
adapter
supplied
with
the
instrument.
When
the
charge
level
reaches
a
point
that
only
a
short
amount
of
operating
time
remains,
a
low-battery
indicator
(E44
)
is
displayed
in
the
upper
right
corner
of
the
readout.
The
oscilloscope
tums
off
automatically
when
the
battery
voltage
drops
below
+7.32
V.
VERT
rotation &)
or DOLCE RaRULATES
SAFETY EARTH
NOT REQUIRED.
A | |
INT CONNECTED TO
COMM PORT GROUND
“~ A
Figure 2-1. External Power Input.
2-1

Operating Information— 222 DSO Preliminary Service
If the charge level of the battery is less than about 20%,
the instrument will not come on without the external
power provided by the battery-charger adapter. Typical
worst-case operating time for an instrument with fully
charged batteries is two hours at normal room tem-
perature with the AUTO TIMEOUT feature turned off.
One or two charged batteries may be carried in optional
pouches that attach to the carrying case for extended
use away from an ac power source. See Battery
Replacement for the battery removal and replacement
procedure.
An external-power-on indicator ( ‘N ) appears in the
upper right corner of the readout when external power is
on. The battery is charging anytime external power is
being supplied and will charge while the instrument is
operating. However, the battery charges faster when the
instrument is not operating. Completely recharge the
battery as soon as possible after each discharge cycle.
Refer to Tips on Battery Care for information on how to
extend the operating lifetime of the battery.
When storing the instrument for periods longer
than two months, fully charge the batteries; then
remove the batteries and store them in a cool
place. Storing partially discharged batteries for
an extended time or in high temperatures can
deplete the remaining charge, leading to a
deep-discharge condition. Refer to Tips on
Battery Care for information on restoring a
deep-discharged battery.
FIRST TIME BATTERY OPERATION
The battery supplied with the oscilloscope is charged at
the factory and shipped unplugged to preserve its shelf
life. However, the state of battery charge at the time you
receive it will be unknown. It is recommended that you
charge the battery for three hours before operating the
oscilloscope the first time.
START-UP
Press
the
button
to
enable
the
display
and
acqui-
sition
system.
Pressing
the
button
a
second
time
turns
off
the
oscilloscope
operation
but
does
not
dis-
connect
the
battery
or
external
power
source.
AUTO TIMEOUT
There is an AUTO TIMEOUT feature that extends the
oscilloscope operating time on battery operation. Witha
two-minute period of no front panel control activity, the
oscilloscope turns off. The acquisition and display can
be turned back on by pressing the button. The
AUTO TIMEOUT feature does not turn off the oscillo-
scope when external power is applied. The feature may
also be disabled from turning off the oscilloscope when
operating on battery power alone. See Section 4 of the
Operators Manual for operating instructions.
VIEWING A SIGNAL QUICKLY
Connect one or both of the probe tips to the signals to be
viewed.
Press ei This gives you a quick setup of the front-
panel controls to view the signals applied to the probe
tip(s). A channel that does not have a signal connected
is turned off (except CH 1 will not be turned off if neither
channel has a signal). If signals are applied to both
channels, each will be autoranged vertically (setting the
VOLTS/DIV and vertical position for each), but the signal
applied to channel 1 will determine the SEC/DIV and
Trigger LEVEL settings. If only channel 2 has a signal ap-
plied, that signal is used to determine the SEC/DIV set-
ting and Trigger LEVEL.
NOTE
AUTO SETUP does not set the SEC/DIV setting
into the ROLL region (0.1 s/div and slower). The
practical
low
frequency
for
using
the
AUTO
SETUP feature is about 20 Hz.
TIPS ON BATTERY CARE
The
battery
in
the
222
is
a
sealed
lead-acid
type
battery
with
four
cells.
These
useful
tips
will
help
extend
the
battery
life.
1. Completely recharge the battery after each dis-
charge
cycle.
Continued
partial
recharges
shorten
the
battery
life.
The
battery
is
on
charge
any
time
external
power
is
used
to
operate
the
instrument.
However,
the
battery
recharges
faster
when
the
instrument is not operating.
2.
Avoid
situations
that
can
lead
to
deep
discharge
of
the
battery.
If
the
instrument
starts
and
remains
on
only
briefly
before
shutting
off,
the
battery
charge
state
is
low.

The
instrument
will
not
start
on
battery
if
the
voltage
drops
below
7.32
V.
The
battery
must
be
recharged
as
soon
as
possible
when
it
is
in
this
state.
Do
not
store
the
battery
or
instrument
with
the
battery
installed
in
a
discharged
state.
Extended
storage
or
Storage
in
high
temperatures
will
deplete
the
remaining
charge,
leading
to
deep
discharge.
When
deep
discharge
occurs,
the
battery
accepts
charge
very
slowly,
and
in
some
cases
may
not
recharge.
3.
If
a
deep-discharge
condition
occurs,
it
may
be
possible
to
recover
the
battery
with
the
following
procedure.
Leave
the
battery
on
charge
for
one
week.
If
it
still
does
not
accept
a
charge,
remove
it
from
the
instru-
ment
and
attempt
to
charge
it
using
a
20
V
power
supply
that
is
current
limited
to
100
milliamperes.
When
attempting
to
recover
the
battery
using
an
external
power
supply,
check
the
battery
frequently
for
the
current-limit
state.
If
the
battery
recovers
from
the
deep-discharge
state,
it
will
pull
the
power
sup-
ply
into
current
limit.
When
this
happens,
reinstall
it
in
the
instrument
and
charge
it
normally.
Do
not
leave
the
battery
on
the
external
power
supply
for
long
periods
of
time
without
checking
it.
If
the
battery
does
not
recover,
dispose
of
it
safely.
4.
When
storing
the
instrument
for
an
extended
period
of
time,
fully
charge
the
battery
and
remove
it
from
the
instrument.
Store
the
fully
charged
battery
in
a
cool
place.
For
short
periods
of
storage,
the
battery
may
remain
installed.
During
“sleep”
mode
the
cur-
rent
drawn
from
the
battery
is
about
1
ma.
With
the
battery
installed,
the
data
stored
in
nonvolatile
memory
will
remain
stored
and
be
available
when
the
oscilloscope
is
turned
on
again.
5.
The
instrument
will
operate
from
the
battery—charger
adapter
or
other
suitable
ac
or
dc
power
source
with
the
battery
removed
from
the
instrument.
BATTERY
REPLACEMENT
If
you
must
often
operate
the
oscilloscope
using
battery
only,
you
may
wish
to
obtain
one
or
two
extra
batteries
and
carry
them
in
a
fully
charged
condition
to
the
servicing
site.
When
the
charge
level
on
the
battery
in
the
oscilloscope
reduces
to
the
shutoff
level,
one
of
the
Spare
charged
batteries
may
be
used
to
provide
more
operating
time.
Remember
to
recharge
a
low
battery
at
the
first
opportunity
to
prevent
it
from
going
into
a
deep
discharge
state.
Operating
Information—222
DSO
Preliminary
Service
The
battery
is
in
a
compartment
behind
the
probe
pouch.
To
remove
and
replace
it,
follow
this
procedure:
If
the
hook
tips
are
not
installed
on
the
probes,
the
exposed
probe
tips
are
very
sharp.
When
handling
the
probes
use
care
not
to
stick
your
fingers
or
the
material
of
the
probe
pouch
with
the
probe
tips.
Open
the
probe
pouch
and
take
the
probes
out
of
the
pouch.
This
allows
the
battery
compartment
cover
freedom
to
move
away
from
the
oscilloscope.
Slide
the
battery
compartment
cover
toward
the
rear
to
disengage
the
locking
tabs.
The
hole
for
the
probe
leads
makes
a
convenient
place
to
apply
the
needed
force
with
your
thumb.
Slide
the
battery
cover
down
the
probe
leads
enough
to
be
able
to
lay
the
cover
down.
Disconnect
the
3-wire
battery
connector
(the
center
conductor
is
the
ground
reference
and
the
two
outer
leads
are
parallel
leads
to
the
positive
side
of
the
battery.
NOTE
If
you
reconnect
power
to
the
battery
connector
from
the
charged
battery
in
less
than
30
seconds,
the
saved
waveforms
and
front-panel
setups
will
not
be
lost.
Lift
the
battery
pack
out
of
the
battery
compartment.
Place
the
charged
replacement
battery
into
the
battery
compartment
with
the
battery
leads
on
the
bottom
side
facing
toward
the
rear.
Reconnect the battery plug.
Slide
the
battery
compartment
cover
back
up
the
probe
leads
and
place
the
cover
locking
tabs
into
the
matching
slots
in
the
battery
compartment.
Make
sure
the
locking
tab
are
all
the
way
into
the
slots
on
both
the
top
and
bottom
of
the
cover.
If
the
tabs
don’t
seat
easily
seat
the
top
tabs
first
then
press
on
the
bottom
of
the
cover
to
seat
the
bottom
tabs.
Push
forward
on
the
rear
of
the
battery
compartment
cover
to
engage
the
locking
tabs.
2-3

Section 3— 222 DSO Preliminary Service
BLOCK DIAGRAM OVERVIEW
INTRODUCTION
The 222 Digital Storage Oscilloscope comprises five
major functional blocks (see Figure 3-1). These are: the
Floating Acquisition System, the Time Base, the
Processor System, the Display System, and the Power
Supplies. The operation of each of these functional
blocks is described. A brief overview follows.
The signal is applied to the Floating Acquisition System
(so named because of the electrical isolation of the
inputs from the remainder of the functional block). There
it is amplified, offset (for position), and limited (to the
dynamic range of the A/D converter). The signal is then
digitized and stored in Acquisition Memory.
An internal trigger signal is also derived from the input
signal. That signal starts events in the Time Base that
cause the acquisition of the input signal to be com-
pleted. (Acquisition is the digitization of the input signal
and storing of the digital values.)
The Processor System transfers the digital waveform
information from the Acquisition Memory to the Display
Memory. That data can then be displayed or stored in the
Save Memory for later recall and viewing. The Processor
System scans the Front-Panel and Top-Panel switches
to determine when the user makes a button press. It also
controls the Time Base, the Acquisition System, and the
Power Supplies. An RS-232C compatible serial port
provides the Processor System with an interface to
external communication devices. Waveform data may
be sent or received over the interface, and the control
settings of the 222 may be changed or queried.
In the Display System the digital waveform data is
converted back to analog signals. These analog signals
are amplified and applied to the crt deflection plates to
provide a visual display of the signal’s waveshape.
Either the internal battery or the external wall transformer
provides the supply voltage for the power supplies. A
battery charger circuit supplies charging current to the
battery and operating power whenever the external
supply is connected to the instrument. The external
power supply may be used to run the instrument with or
without the battery installed. Separate supplies provide
power for the crt, the Floating Acquisition System, and
the remaining digital circuitry of the instrument.
ACQUISITION SYSTEM
The Acquisition System contains two complete, isolated
vertical channels, each with its own attenuator,
amplifier, trigger circuit, A/D converter, peak detector,
acquisition memory, and isolated power supply (see
Figure 3-2). The channel grounds are isolated from each
other and instrument ground. Data and clock signals are
passed through pulse transformers and opto-couplers
to maintain the isolation.
The attenuator, amplifier, and trigger circuit for each
channel are formed by a hybrid circuit on a single
ceramic carrier. Passive attenuators provide X1, X10,
X100, and X1000 attenuation of the input signal. The gain
amplifier has a high input impedance and a low output
impedance. A high-speed trigger pulse is derived from
the input signal by the trigger circuit portion of the hybrid
component. Output signals from the amplifier are in the
range of 0 to 2.5 V to be applied to the A/D Converter.
Output voltage samples from the amplifier are converted
into 8-bit digital words. Conversions occur at a sample
rate of 10 MHz that does not change with the SEC/DIV
setting. To provide lower sampling rates of the input sig-
nal, the data words are stored in the acquisition memory
at a save clock rate that does varies with the SEC/DIV
setting.
The Acquisition Memory is a FIFO (first in, first out)
memory system. The length of the data pipeline is 512
data bytes (of 8 bits each). In the normal sample mode,
each data byte produced by the A/D Converter is stored
into the pipeline at the sample clock rate (10 MHz). At
Time Base settings above 5 ys/div, the save clock rate
(which changes with the SEC/DIV setting) is used to
store converted sample into the pipeline. With PEAK
DETECT enabled, two data bytes are stored into the
pipeline for each save clock. The data bytes are loaded
into
a
shift
register
at
the
output
of
the
FIFO
and
the
bits
of
the
data
byte
are
shifted
out
serially
through
an
isolation
pulse
transfer
to
be
placed
into
the
display
memory for eventual display.
3-1

Block Diagram Overview— 222 DSO Preliminary Service
FLOATING ACQUISITION SYSTEM PROCESSOR SYSTEM
SIG A/D FRONT
COMM
MEMORY PORT /“—7> RS-232C
CLK
—F pry
SAMPLE CLK
GENERATOR
EXT TRIG
come | >
= I | ] DISPLAY SYSTEM
oe Y
DISPLAY
CONTROL || 2-AMP
RECORD | | PRE-FILL
COUNTER| | COUNTER
Bl
Vv
TIME BASE i
L_ 1 X-AMP
EXT
VECTOR
TRIG
GEN
\—e—1 Y-AMP
POWER SUPPLY
+5 DVcc Apt
_ +5.3V
+5 Voc ey ISOLATED
SWITCHING
SUPPLY
EXT BATTERY H
POWER —T "| CHARGER +8.8V +e vues 100 V ieay
ae ISOLATED
Figure 3-1. Simplified block diagram of the 222 DSO.
3-2

Block Diagram Overview — 222 DSO Preliminary Service
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U122C,D 13 B
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Figure 3-2. Floating Acquisition System.
3-3

Block Diagram Overview— 222 DSO Preliminary Service
TIME BASE
All acquisition clock signals are derived from a free-
running, 20-MHz master oscillator. The Sample Clock
Generator contains counters and multiplexers to pro-
duce the various clocking signals to the A/D Converter,
the Acquisition Memory, and the data counters that keep
track of the number of samples taken for a waveform
record.
The Pre-Fill Counter counts to determine when the
pretrigger waveform data has been acquired. Then the
trigger circuit is enabled to accept a trigger event. When
the trigger occurs, the remaining data points needed to
fill the waveform record are acquired. The Record
counter determines when those data points have been
acquired, then halts the acquisition system. A complete
waveform record is then held in the Acquisition Memory.
An interrupt is also generated to the Processor to inform
that device that the acquisition is completed.
The output of the Clock Delay circuit is used during
Repetitive Store Mode. The time difference between the
trigger event and the rising edge of the sample clock is
measured so that repetitive samples taken on different
triggers may be correctly placed in the waveform record.
The resolution of the Clock Delay timer is 0.5 ns.
When external trigger signals are connected to the
instrument, the External Trigger Comparator is used to
produce the actual trigger event from the applied
signals. For operation on internal trigger signals, a
Schmitt trigger circuit is used. This provides more noise
immunity so a false trigger is not produced.
PROCESSOR SYSTEM
The Processor System contains a microcontroller, a
memory,
chip-select
logic,
and
the
RS-232
interface
(see
Figure
3-3).
It
receives
inputs
from
the
Front
Panel
or RS-232 interface and controls the Acquisition
System, Time Base, and Display System through its
synchronous
serial
interface.
The
Processor
System
is
clocked
by
an
8
MHz
oscillator
that
is
not
frequency
3-4
related to the Time Base clocks (not derived from the
20 MHz Time Base oscillator).
Microprocessor
The heart of the Processor is an 8-bit microprocessor
with built-in RAM, ROM, EEPROM, Timers, A/D Con-
verter, and serial and parallel ports. An internal crystal-
controlled, 8-MHz oscillator produces the timing for all
the Processor and Display operations.
The microprocessor has its own internal reset circuitry
for handling power down and does not require an
external reset circuit. However, the EEPROM circuitry
requires some handling on loss of power to maintain its
stored data intact. A reset signal is generated when the
voltage falls below 6 volts.
A dedicated address bus is used for addressing the
ROM, the address decoders and timers of the Processor
Circuitry.
The internal ROM of the microprocessor contains the
diagnostic routines used to check out the external
devices on the bus when the EEPROMS cannot be
accessed.
The Display Memory is formed by an external 32K by 8
bit static CMOS RAM that is accessed by the micro-
processor for loading in waveform data or reading out
waveform data when it is being sent over the RS-232
interface.
An internal A/D Converter in the microprocessor is used
to encode the Front Panel potentiometer settings and
monitor the battery voltage level.
Control data used to set the external devices for such
things as gain, attenuation, and time base multiplexing
is sent simultaneously to the Display System, the Acqui-
sition System, the Front Panel, and the Acquisition Con-
trol latch. The Display System only accepts serial data
when its select line is high. The Front Panel, Acquisition
Control Latch, and the Acquisition System latches are
strobed so that only the desired latch is loaded when the
serial data needed for a chosen latch is sent.