Tektronix 221 User manual

TEKTRONIX
OSCILLOSCOPE
SERVICE
INSTRUCTION MANUAL
Tektronix, Inc.
P.O. Box 500
Beaverton, Ore on 97005
070-1573-01

WARRANTY
All TEKTRONIX instruments are warranted a ainst
defective materials and workmanship for one year. Any
questions with respect to the warranty should be taken up
with your TEKTRONIX Field En ineer or representative.
All requests for repairs and replacement parts should be
directed to the TEKTRONIX Field Office or representative
in your area. This will assure you the fastest possible
service. Please include the instrument Type Number or Part
Number and Serial Number with all requests for parts or
service.
Specifications and price c
. % & & * & '** * * *
Copyri ht 1973, new material 1974, by Tektronix,
Inc., Beaverton, Ore on. Printed in the United States of
America. All ri hts reserved. Contents of this publication
may not be reproduced in any form without permission of
Tektronix, Inc.
U.S.A. and forei n TEKTRONIX products covered by U.S.
and forei n patents and/or patents pendin .
TEKTRONIX is a re istered trademark of Tektronix, Inc.
http://m Q nom Qn .sqhill.co m

221 Service
T BLE OF CONTENTS
SECTION 1 OPERATING INFORMATION
AND SPECIFICATIONS Pa e SECTION 5 CALIBRATION (cont)
PRELIMINARY PROCEDURE
Pa e
5-2
INTRODUCTION 1-1 PRELIMINARY CONTROL
ELECTRICAL 1-1 SETTINGS 5-2
Vertical Deflection System 1-1 INDEX TO CALIBRATION
Tri erin 1-1 PROCEDURE 5-3
Horizontal Deflection System 1-2 POWER SUPPLY 5-4
Display 1-2 DISPLAY 5-6
Power 1-2 VERTICAL SYSTEM 5-7
PHYSICAL 1-3 SWEEP TRIGGER 5-11
HORIZONTAL SYSTEM 5-12
SECTION 2 FUNCTIONS OF CONTROLS
AND CONNECTORS 2-1 SECTION 6 TROUBLESHOOTING AIDS
SECTION 3 PREVENTIVE MAINTENANCE Dia rams 6-1
Troubleshootin Equipment 6-1
Disassembly 3-1 Component Color Codin 6-2
Cleanin 3-1 Isolatin Trouble To A Circuit 6-2
Visual Inspection 3-2
Semiconductor Checks 3-2
Recalibration 3-3 SECTION 7 CORRECTIVE MAINTENANCE
Obtainin Replacement Parts 7-1
SECTION 4 CIRCUIT DESCRIPTION Component Replacement 7-1
Recalibration After Repair 7-2
BLOCK DIAGRAM 4-1 Instrument Repacka in 7-2
CIRCUIT OPERATION 4-1
Vertical Amplifier 4-1 SECTION 8 ELECTRICAL PARTS LISTS 8-1
Tri er Sweep 4-3
Horizontal Amplifier 4-5
Power Supply 4-6 SECTION 9 DIAGRAMS, CIRCUIT BOARD
CRT Circuit 4-8 ILLUSTRATIONS
SECTION 5 CALIBRATION SECTION 10 MECHANICAL PARTS LISTS 10-1
TEKTRONIX FIELD SERVICE 5-1
TEST EQUIPMENT REQUIRED 5-1 CHANGE INFORMATION
REV. B, AUG. 1974

Fig. 1-1. The Tektronix 221 Oscilloscope.
221 Service
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OPER TING INFORM TION
ND SPECIFIC TIONS
Section 1—221 Service
INTRODUCTION
The 221 Oscilloscope is a sin le-channel, five me ahertz
portable instrument usin all solid state and inte rated
circuit components (except the crt). The instrument is
mechanically constructed to withstand the shock, vibration,
and other extremes associated with portability.
The dc to five me ahertz vertical system provides verti
cal deflection factors from five millivolts to 100 volts/
division at the tip of the inte ral hi h-impedance probe.
The tri er circuit provides stable tri erin over the full
ran e of vertical frequency response.
The horizontal deflection system provides calibrated
sweep rates from 200 milliseconds to one microsecond/
division. A sweep variable decreases calibrated sweep rates
by about 2.5:1, resultin in a minimum uncalibrated sweep
rate of about 0.5 second/division. A calibrated X10 sweep
ma nifier increases the sweep to at least 0.1 microsecond/
division. In addition, horizontal amplifier operation pro
vides a horizontal deflection factor of one volt/division for
X-Y operation. The cathode-ray tube has a six by ten
division raticule (each division equals approximately
0.2 inch).
The 221 is operated either from ac line volta e or from
internal rechar eable batteries. The internal batteries are
rechar ed from the ac power line by the inte ral battery
char er (with the instrument on or off).
This instrument will meet the followin electrical char
acteristics after complete instrument calibration. These
characteristics apply over an ambient temperature ran e of
—15°C to +55°C (+5°F to +131°F) when battery operated,
or 0°C to +40°C (+32°F to +104°F) when the instrument is
connected to ac line volta e. Warmup time for iven
accuracies is five minutes.
ELECTRIC L
The 221 oscilloscope will meet the followin electrical
specifications after calibration. The check portion of the
calibration procedure provides a convenient method of
checkin instrument performance without makin internal
checks or adjustments.
The followin electrical characteristics apply over an
ambient temperature ran e of —15°C to +55°C (+5°F to
+131°F) battery operation, or 0°C to +40°C (32°F to
+104°F) for line volta e operation.
Vertical Deflection System
Calibrated Ran e: five millivolts to 100 volts/division in
14 steps.
Accuracy: within 3% with VAR VOLTS/DIV in CAL
detent position.
Uncalibrated VAR VOLTS/DIV ran e: Continuously
variable, 3:1 minimum.
Bandwidth (with six division reference): to at least
five me ahertz (—3 dB point), with VARIABLE VOLTS/
DIV in CAL position.
Step Response: 70 nanoseconds or less.
Aberrations: +5%, —5%, 5% peak to peak total.
Input Resistance: 1 me ohm.
Input Capacitance: Approximately 29 picofarads.
Maximum Safe Input Volta e: 600 volts (dc + peak ac),
600 volts peak-to-peak ac.
Triggering
Tri er Sensitivity:
INT: 0.5 divisions from two hertz to one me ahertz,
increasin to 1 division at five me ahertz.
EXT: 0.5 volt from dc to one me ahertz; increasin
to 1 volt at 5 me ahertz.
AUTO PRESET: Tri ered at preset level on positive
slope of waveform.
Display Jitter: 20 nanoseconds or less.
EXT TRIGGER:
Input Resistance: Approximately one me ohm.
Input Capacitance: Approximately 30 picofarads.
Maximum Usable Input Volta e: Three volts (dc +
peak ac), six volts peak-to-peak ac (five me ahertz of less).
REV. B, FEB. 1976 1-1

Operating Information and Specifications—221 Service
Horizontal Deflection System
Sweep Generator:
Calibrated Ran e; 200 milliseconds to one microsecond/
division in 17 steps.
Accuracy (over center ei ht divisions): Within 3% with
VAR SEC/DIV in the CAL position.
Linearity (any two division portion, within the center
ei ht divisions): Within 3%, disre ard first 1 microsecond
of sweep.
SEC/DIV VAR (Variable): Continuously variable
between calibrated settin of the SEC/DIV switch. Extends
minimum sweep rate to approximately 0.5 s/div. Each
sweep rate is decreased 2.5:1.
Horizontal Ma nifier (HORIZ-MAG 10X) Calibrated
ma nifier when SEC/DIV is in CAL detent. Accuracy
within 5%, disre ard the first 1 microsecond of the
sweep.
External Horizontal Input:
Deflection Factor: One volt/div IX, 0.1 volt/div 10X.
Accuracy within 10%.
Bandwidth: With six division reference dc to
500 kilohertz.
Input Resistance: Approximately 500 kilohms.
Input Capacitance Approximately 30 picofarads.
Maximum Safe Input Volta e: 200 volts (dc to peak ac),
200 volts peak-to-peak ac.
Maximum Usable Input Volta e: Approximately
± nine volts.
Display
Graticule:
Type: Internal back line, non-illuminated.
Area: Six vertical divisions by 10 horizontal divisions.
Phosphor: P31 Standard.
Power
Line Volta e Operation:
Line Volta e Ran e: 90 V to 250 V ac; 80 V to 250 V dc.
Line Frequency Ran e: 48 to 62 Hertz.
Maximum Power: Five watts.
Line Fuse: 0.2 A 250 V.
Common Isolation:
Line Operation: Line volta e plus floatin volta e not
reater than 250 volts RMS sine wave, or 1.4 times line
volta e + dc + peak ac floatin volta e not reater than
350 volts.
Battery Operation: Common to outside of case
floatin volta e not reater than 500 volts RMS or
700 volts dc + peak ac.
Battery Operation:
Batteries: Ten rechar eable A nickel-cadmium cells.
Char e time: 16 hours for full char e.
Battery Char e Indicator- Battery meter indicates Full,
Low and Rechar e. Rechar e is indicated after automatic
shut-off turns instrument off.
Battery Dischar e Char e Protection: Instrument opera
tion automatically interrupted when battery char e is less
than 10 volts.
Typical Operatin Time (after full char e cycle at +20°C
to +30°C): Two to three hours. Lon est operatin time
provided at low trace intensity.
Typical Char e Capacity
(Referenced to char e/dischar e at +20°C to +30°C):
T BLE 1-1
CH RGE OPER TING TEMPER TURE
TEMPER TURE +15°C +20° C to +30° C +55° C
0°C (+32° F) 40% 60% 50%
+20° C to +30° C 65% 100% 85%
(+68° F to +86° F)
40° C (+104°F) 40% 65% 55%
1-2 REV. B, FEB. 1976

Operating Information and Specifications—221 Service
PHYSIC L
Temperature:
Operatin from Batteries, -15°C to +55°C (+5°F to
+131°F).
Char in or operatin from ac line, 0°C to +40°C
(+32°F to +104°F).
Stora e, -40°C to +60°C (-40°F to +140°F).
Humidity (operatin and non-operatin ): 5 days 50°C to
95% relative humidity.
Shock (operatin and non-operatin ): Tested with two
shocks at 100 , one-half sine, two millisecond duration
each direction alon three major axes.
Wei ht (without accessories):
3.5 pounds (1.5 kilo rams)
Altitude:
Operatin , to 25,000 feet (maximum operatin tem
perature decreased by 1°C per 1,000 feet shown above
15,000 feet).
Dimensions (measured at maximum points):
Hei ht: 3.0 inches (7.6 centimeters).
Width: 5.25 inches (13.2 centimeters).
Non-operatin , to 50,000 feet. Depth: 9.0 inches (22.8 centimeters).
REV. APR 1974 1-3

FUNCTIONS OF
CONTROLS ND CONNECTORS
Section 2—221 Service
All controls and connectors necessary for operation of
the 221 are located on the ri ht side panel of the
instrument. See Fi . 2-1. A brief description of each control
and connector is iven here.
VOLTS/DIV—selects vertical deflection factor (VAR
VOLTS/DIV must be in the CAL position for indicated
deflection).
STEP ATTEN BAL—screwdriver adjustment to balance
the vertical system for minimum trace shift when chan in
deflection factors.
Vertical POS—controls the vertical position of the trace.
VERT GAIN—screwdriver adjustment to set the ain of
the vertical system.
VAR VOLTS/DIV—provides a continuously variable
deflection factor between the calibrated settin s of the
VOLTS/DIV switch.
INPUT COUPLING—selects method used to couple the
input si nal to the vertical amplifier system.
AC—blocks dc components of input si nal. Low
frequency limit (—3 dB point) is about two hertz.
GND—Input circuit is rounded. The applied si nal is
connected to round throu h a lar e resistor to provide a
prechar e path for the AC input couplin capacitor.
DC—All components of the input si nal are passed to the
vertical amplifier system.
SEC/DIV selects the sweep rate (VAR SEC/DIV must be
in the CAL detent; HORIZ MAG must be in XI position,
for indicated sweep rate). 1 V position allows for X-Y
operation with the horizontal deflection provided by the
si nal connected to the EXT TRIG OR HORIZ INPUT
jack.
Horizontal POS—controls the horizontal position of the
trace.
VAR SEC/DIV—provides continuously variable sweep
rates between calibrated settin s of the SEC/DIV switch.
Extends the minimum sweep rate to about
0.5 second/division.
HORIZ MAG—X10 ma nifier to increase the maximum
sweep time to 0.1 microsecond/division and provides a
horizontal sensitivity of 0.1 volt/division in X-Y operation.
Fig. 2-1 Side panel showing controls and connectors.
REV. B, FEB. 1977 2-1

Functions of Controls nd Connectors—221 Service
VOLTS/DIV
Fig. 2-2. Side panel showing controls and connectors.
SWP CAL—screwdriver adjustment to set the basic
timin of the horizontal system.
TRACE ROTATION—screwdriver adjustment to ali n
trace with raticule lines.
EXT TRIG OR HORIZ INPUT—banana jack for input of
an external tri er si nal or for input of an external
horizontal (X) si nal for X-Y operation.
LEVEL/SLOPE—selects the amplitude point and slope
of the tri er si nal on which the sweep is tri ered. When
the indicator dot is to the left of center, the sweep is
tri ered on the positive- oin slope of the tri er si nal; to
the ri ht of center, on the ne ative- oin slope. When the
LEVEL/SLOPE control is set to the AUTO PRESET
detent, the sweep is automatically tri ered at a preset level
on the positive- oin slope.
AUTO PRESET—screwdriver adjustment to set the
PRESET tri er point for AUTO sweep operation.
EXT-INT—selects the source of the tri er si nal.
INTENSITY—controls bri htness of crt display (detent
turns OFF instrument power).
FOCUS—screwdriver adjustment to obtain a well-defined
display
BATTERY—expanded scale meter to indicate the
relative char e level of the internal batteries.
POWER—(counterclockwise detent of the INTENSITY
control). Controls power to the instrument. Does not
interrupt char in current to the internal batteries when
connected to an AC line volta e.
COMMON—banana jack to establish common round
between the 221 and the external si nal source or
equipment under test.
2-2 REV. B, FEB. 1977

Section 3—221 Service
PREVENTIVE M INTEN NCE
Preventive maintenance, when performed on a re ular
basis, can prevent instrument breakdown and may improve
the reliability of the 221. The severity of environment to
which this instrument is subjected will determine the
frequency of maintenance. A convenient time to perform
preventive maintenance is precedin recalibration of the
instrument.
Disassembly
To ain access to the interior of the instrument, unwind
the probe and the power cord from the rear of the
instrument. Remove the five screws in the bottom cover of
the instrument. See Fi . 3-1. Gently separate the bottom
cover from the instrument and lay aside.
If access to the front of the Input circuit board is
necessary, remove the knobs from all of the external
control shafts. Remove the two screws securin the side
panel to the Input circuit board and remove the instrument
side panel.
Cleaning
The 221 should be cleaned as often as operatin
conditions require. Accumulation of dirt in the instrument
can cause component breakdown.
The hi h impact plastic covers provide protection a ainst
dust in the interior of the instrument. Loose dust accu
mulated on these covers can be removed with a soft cloth
or small brush. The brush is also useful for dislod in dirt
on and around the side panel controls. Dirt that remains
can be removed with a soft cloth dampened in a mild
deter ent and water solution. Abrasive cleaners should not
be used.
Cleanin the interior should only be occasionally neces
sary. The best way to clean the interior is to blow off the
dust with a dry, low-velocity stream of air. A soft-bristle
brush or a cotton-tipped applicator is useful for cleanin in
narrow spaces or for cleanin more delicate components.
Avoid the use of chemical cleaning agents which
might damage the plastics used in this instrument.
Avoid chemicals which contain hydrochloric acid,
sodium hydroxide, or sulfuric acid.
REV. APR 1974 3-1