Tektronix 485 User manual

TABLE OF CONTENTS
485/R485 Service
SECTION 1SPECIFICATION
Pogo SECTION 3CIRCUIT DESCRIPTION (conti
p,,.
Introduc1ion
,.,
Focus DC Restorer 3-13
V.tical Deflection SyRem
... Beam Current Limit 3-14
Probe Perlormanu
...,
Po_r Supply Shutdown Ceused by
A tlOd B Triggerin;
,~
Excessi.... Beam Current 314
Horizontal Deflection
'4
CRT Control Circuits 3-14
Calibrated Sweep Delay
'4
Auto Focu' Circuit 3-14
X·Y
,~
Calibrator 3-15
CRT
H
Calibrator
,~
Other CharacteriRics
,~
SECTION 4 MAINTENANCE
Ell'lironmental CharactMiRics
,~
IntroduC1ion 4-,
Cover Removal and Reinstallation 4-,
SECTION 2OPERATING INSTRUCTIONS Cleaning
,.,
Lubrication
'.'
Gen .... 1
,.,
Visuallnlf)aC1ion
'·3
Praliminary Information
,.,
Semiconductor Checks 4-3
Controls and Connection'
'.,
Recalibration
'·3
Front Pane!
,.,
Troublll$hootin;
,~
Rear Panel
'4
Introduction
'·3
Bottom Side
'4
Troublashootin; Aids
'·3
Circuit Board.
,~
Troublashoo1in; Equipment
,~
Troubllt'ShOOlin; Techniques
,~
SECTION 3CIRCUIT DESCRIPTION Special
Troubleshooting Information
4-,
Correcti ... Mainter'anca 4-11
Introduction
3·'
Dblainillll Replacament Paru
4·11
50 n A ttenuttor
3·'
Solderillll Tachniques
4-11
1Megohm
Buffer Amplifier
3·'
Component Repl_ment
4-12
50 nOverload Protection
3·'
Circuit Board Repl_ment 4·12
V.tical Preamplif • .,
3·'
Timin; Board Removal 4-12
Transform" Board Remonl
4·13
Signal Channel Switch
3·'
InYartar Board Removal 4_14
Internal Trigger Amplifiar
3·'
Semiconductor Replacement
4-14
Main Vertical Amplifier
3·'
Circuit Board Pin'
4·14
Scale Faetor Readout
3~
End Lead Pin Connectors
4·15
Vertical Mode Control
3~
Cathode Ray Tuba Repl_ment
4-15
ZAxis 3·3 Rapachllillll
for Shipmant
4·15
ATrig9er Amplifier
3~
Inlarboard C9mb Connection Loutions
4-"
AEXT Trigger Identify 3~
A Triggoer Gen .... ,or 34
SECTION 5 CALIBRATION
B Tr.r Generator J.4
Introduction
5·'
A and B Sweep,
J.4
TEKTRON IX Field Sllt'Yiea
5.'
Horizontal Amplifier
3~
Usin; Thi, Procedure
5·'
Horizontal Control 3~ Test Equipment Required
5·'
Power Inverter/Regulator
~
Special Calibration Filltures
5·'
Line Filt.,
3~
Calibrttion Equipm""t AII.,nalil/ft
54
Line Input Circuil
3~
Perlormance Check
54
Slart Natwork
'.'
Calibration Procedure 5~
Inverter 3~
I nvart.,/R'lIulltor 3~
lnvarter Currant Limitillll Circuit
,~
SECTION 6RACKMQUNTING
OvlltVoltage Stop Circuit
3~
Introduction
,.,
L1na Stop Circuit and Surge Limiting 3~
Rack Dimension,
,.,
Procedure for Converting the 485 to
Slida Out TtlICks
6·'
DC Operation 3~
Mounlin; Procedure
6·'
low Volt. Supplies
,.,
Alter"'te RNr Mounting Methods
5·'
Power Supply Protaetion Circui1 3·10
Removing Or ln$larung thaln$lrumant
,.,
Stop Mono$lable 3·10
Slida Out Track Lubrication
,.,
Balenea Nod. 3·10
Overcurrant Protection 3-12 SECTION 7ELECTRICAL PARTS LIST
Low Line Voltage Protaction 3·12
Samplin; Period Ti..- and Dver_ SECTION 8DIAGRAMS
AND CIRCUIT BOARD
Voltage Protection 3·12
CRT Clfcuil 3-12 ILLUSTRATIONS
Filament Voltage
3·12
His;, Volt. Supplies 3-12
Anode Supply 312 SECTION 9 MECHANICAL PARTS LIST
C,thode SupplV 3-12
Cathode Regulator
3·12
Grid DC RlI$Iorar 3-13 CHANGE
INFORMATION
REV. B. MAR. 1976

Section 1--485/R485 Service
SPECIFICATION
Introduction
The 485/R485 is ageneral-purpose, environmentalized,
high·performance, portable, wide-band oscilloscope which
has adual-channel vertical amplifier with selectable input
impedance (DC to 350 MHz bandwidth with 50 il input
impedance; DC to 250 MHz bandwidth with 1 Mil input
impedance). The 485 has a 1 ns sweep rate, stable triggering
to bandwidth limits and calibrated X-V capabilities.
Delayed sweep has calibrated delay time, can be triggered
aher delay and can be displayed with the intensified main
sweep
in an alternate sweep switching display. Additional
features are XtO, X100
probe scale factor readout, 8div
Xl0 div graticule area, small spot size and high writing rate.
A
20 MHz bandwidth limiter, 1 MHz and 1kHz last·rise
calibrator
and autofocus are also included. The 50 n input
is automatically disconnected from excessive Voltages. An
external trigger view feature
is also provided. The 485·1 and
485-2 have no external trigger view. The
485-2 has Only 50
nvenical input impedance.
Input Coupling Selection
AC; DC; GND (provides zero reference, precharges
coupling capacitor, disconnects
50 nload in 50 n
model.
Lower -3 dB Point (AC coupling from 50 n
source)
50 ninput, 1kHz or less.
1
Mn input lX, 10 Hz or less.
Deflection Factor
5mV/div to 5V/div in 10 calibrated steps (1-2·5
sequence), accurate within
2%. Uncalibraled, continuo
ously variable between steps
to al least 12.5 V/div.
Lights at edge of knob skirts indicate correct defleClion
faclor for 1
X, lOX and l00X probes.
ELECTRICAL CHARACTERISTICS
Gain can be recalibfated at fronl panel. 1 Mil SAL is
available at botlom panel to eliminate step allenuator
shift above to mV/div, in the 1 Mn mode.
VERTICAL DEFLECTION SYSTEM
(2 identical channels)
Display Modes
Channell; Alternate; Chopped (approximatelv 1 MHz
rate); Added; X·Y (CH 1 -y and CH 2 -XI; Channel 2
(+Up
or Inverted).
(VARIABLE gain
Terminated Source
,
,
-
c..---
--
TYPICAL BANOWIOTH. 50 n
VS.
VARIABLE GAIN SETTING
300
BW.
MH.
200
Internal Trigger Source
Normal (displaved signal). Channel 1 or Channel 2
signal.
500
400
BandwidthIand Risetime2
CALIBRATED3) From son
_15°C to +35°C
From 50 nterminated source -1SoC to +35°C.
1
Mn within 1% paralleled by approximately 20 pF.
50 nDC to at least 350 MHz, 1ns
Selectable Input Impedance
50 nwithin 0.5%. VSWR t;;;;1.25: 1on 5mV/div and
10 mV/div, 1.15:1 Irom 20 mV to 5V!div to 350 MHz.
1
Mn DC to at least 250 MHz, 1.4 ns
Fill. 1·1. Typical Bandwidth, 50 n vs. Vari.bl. G;oinSIII;ng tvaries
considerablv depending on instrumant SNI
,.,
1 Bandwidlh tBWI mellsure<! 81 -3 dB down.
lRiSBlime c;otcul;oled trom O.35/BW. From +35°C 10 +55°C, BW is
300 MH~ for 50 0 and 200 MH~ for 1 MO.
)Sea Fi9. 1·1 for effect of VARIABLE gain conlrol.
REV C. MAR 1979
so
SO%
Per<;ent of CAL Gain
'00%

Speeification-485/R485 Service
200 V
100 V
60V
<DV
20V
10V
'V
2V
":::::
~~
~
""'-
150 V
~~E~A~ !,~CING-..~
~
h.
~
~
~
1 m,
50V
"'-,- TYPICAL
'"
50 n PROTECTION_
~o,."' ....
DISCONNECT
Oi$l;onnlll;:1
CHARACTERISTIC
Threshold
l
::::
Ilatd!if'llJl
~o,
.......
~
-"
' ...
NONRECURRING SIGNALS
..............
IN THIS AREA 00 NOT
TRIP THE DISCONNECT
............ ~1
-"
, ....
5V
1 V 0.1 ms
50 nProtection
10 rnl
Tima from 5urt of Applied Voltage
Fig. 1-2. Typical 50 n Protection Disconnect Charae:teristic.
Bandwidth limiter
0.1 s1 •
Internal detection circuitry automatically disconnects
excessive signals of up to 50 V. The disconnected
condition is indicated, and has manual reset.
Maximum Input Voltage
50 nDisconnect occurs for voltages that exceed approx,
imately 5 V
RMS continuous or 0.1 watt-second for
instantaneous voltages of 5 V to 50 V.
Repeated application of voltages in excess of 50 volts
and greater than 0.1 watt-second will cause deterioration
of K1S1 relay contacts. due to arcing. Signals in excess
of 150 volts will damage the instrument.
1
Mil·DC coupled 250 V (DC +peak ACI. 500 V pop to
1kHz. AC coupled 500 V(DC +peak ACI. 500 V pop to
1kHz.
Common Mode Rejection
Added Mode with Channel 2invened. At least 10:1 at
50 MHz for a·division
signal after adjusting CH 2gain
for
best CMR at 50 kHz and 20 mV/div.
1-2
Limits to approximatelv 20 MHz the Vertical Amplifier
and Internal Trigger signals.
Channel Isolation
At least 30:1 at 350 MHz.
A Ext Trigger Display (R485 and 485 only)
Momentary pushbutton in VERT MODE area enables
display
of EXT ATrigger when Asource is in EXT
position. Deflection factor is approximatelv 50 mV/div.
Risetime
is approximately 1.5 ns. Delav match to CH 1
or
CH 2 input is within 0.5 ns at 50% amplitude.
Triggering level
is within 0.5 div of center-screen.
Probe Power
Two 4-pin connectors at the rear of the instrument
provide power suitable for optional active probes
such as
the P6201.
®i

Specification-485/R485 Service
PROBE PERFORMANCE
(Probes are Optional Accessories)
Temperature Range
Lower Bandwidth for this
Input
-3 dB point with
485
Bandwidth
Type Atten. Impedance (maximum) (minimum) Specification
For Use WIth
50 nInput
010-6056·03
~ 6ft.
P6056
lOX 500!"! 1 pF
200 Hz 350 MHz
010-6056·05 -9ft.
010·6057·03 - 6 ft.
_15°C to +35°C
P6057 100X 5k!"! 1
pF 20 Hz
350 MHz
010·6057-{)5 - 9ft.
1X 100 kn 3pF 10 Hz
P6201 010·6201·01
-6ft.
Plug·
lOX 1 MS1 <1.5 pF
1 H,
330 MHz
DoC to +35°C
(FET Probe)
00
100X 1 MS1 <1.5 pF 10 Hz
For Use With 1 Mil Input
010·6053·11 -
3112lt.
1M!"! 9.5 pF
250 MHz
P6053A
010·6053·13 -6ft. lOX 1M!"! 12
pF 1 H,
250 MHz
-lS0Cto+35°C
010·6053·15 -9ft. 1M!"! 13.5 pF 200 MHz
Aand B TRIGGERING Time Base Aand BTrigger Sensitivity
Trigger Mode To 50 MHz At 350 MHz
DC lot 0.3 div 1.5
div
DC Ext 20 mV 100 mV
AC
Signals below 16 Hz are attenuated.
LF Reject Signals below 16 kHz are attenuated.
HF Reject Signals below 16 Hz and above 50 kHz
are attenuated.
Sweep free·runs
in the absence of atriggering signal
and lor signals below 20 Hz.
Sweep runs only when triggered.
Sweep runs one time on the first triggering event
alter
pressing the reset selector.
AUTOMATIC.
SINGLE SWEEP.
ATrigger Mode
NORMAL.
level and Slope
BTrigger Mode
BRUNS AFTER DELAY TIME.
Starts automatically
at the end of the delay time.
Internal, permits selection of triggering point at any
level
on the positive and negative slope of the displayed
waveform. External,
level is adjustable through at least
to.5 Vfor either polarity It5 Vfor EXT +10l.
BTRIGGERABLE AFTER DELAY TIME.
Runs when triggered. The B(delayed) sweep runs
once, in each of these modes, following the Asweep
delay time.
ASource
Internal, Line, External, External +10.
REV. B, AUG. 1977 1-3

SpeCification--485IR48S Service
BSource
Bruns after Delay Time, Internal, External, External
+10.
Minimum Sweep Holdoff (A Trigger Holdoff in
Norm
detent)
ATime Setting
External Inputs
1Mil paralleled by approximately 20 pF. Maximum
input voltage 500 V
(DC +peak AC), 500 V p.p to
1kHz.
Jitter
less than 0.1 ns at 350 MHz and 1nsldiv.
1ns/div
to 0.1 ~s/div
0.2 ~s/div
0.5 ~s/div to 0.5 s/d;v
ATrigger Holdoff
less than 0.4 ~s.
Less than 1.0 IJ.s.
Less than 2times the
ATIMEIDIV setling.
HORIZONTAL OEFLECTION
Time Base Aand B
1nsldiv to 0.5 sldiv in 27 calibrated steps /1-2·5
sequence). Uncalibrated, A is continuously variable
between steps and to at least 1.25 sldi ....
Adjustable control permits astable presentation of
repetitive complex waveforms. The control covers at
least the time of one full sweep for sweeps faster than
0.2 s/di ....
BEnds A
The Asweep is reset at the end of the Bsweep to allow
the fastest possible sweep repetition rate for increased
trace intensity
in the delayed sweep mode.
CALIBRATED SWEEP DELAY
Delay Time Range
o 10 9.9 times the Delay TimelDiv settings of 10 ns/div
to
0.5 s/di ....
Exclude the first (above 0.0) 1.0 turn or the first 40 os
of
the DELAY dial.
Differential Delay Time Accuracy (+1S'"C to
+35"Cl
'Full sca'e i110X Ihe OeillY Tima/Oiv Sening.
Time Base Aand BSweep Accuracy (Center 8
screen divisions)
Sweep Rate +lS'"C
to +3S'"C
-lS'"C to +SS'"C
1nsldiv to 20 nsldiv '3% '5%
50 nsldiv to 0.1 sldiv '2% "'I'
0,2 sldi ... to 0.5 sldi ...
'3% '5%
Display Modes
A, A INTEi~sified during Bdelayed, ALTernate display
of AINTEN and B(delayed sweep), Only Asweep
is
displayed for Asweep rates of 1,2 and 5ns/div.
1-4
DELAY TIME Setting
10 ns/div and 20 ns/div
50 ns/div to 1ms/div
2ms/div to
0.5 s/div
± (1% of mt:8surement
+0.2% of full
scale')
±(0.5% of measurement
+0.1 %of full scale)
± (l%of measurement
+0.1 %of full scale)

•
,.,
,.,
SPECIFIED OIFFERENTIAL
OELAY ACCURACY
V,.
SIZE OF MEASUREMENT
10 n .. div 80 20 ntldiv
2mild;" 10 0.5 sid;"
Specification-485/A485 Service
CRT
TEKTRONIX CRT
4-inch rectangular tube; ax 10 divisions (0_8 cm/div)
display area.
P31 phosphor normally supplied; Pl1
optional without extra charge. 21 kV accelerating
potential.
50 nsld;" to 1 mildi ..
~IO.5'" of me.", •• mlnt
+0.'% of lull lUll)
DIFFERENCE Batween Two Dial
Raad;n!p,1Y.3je" D,T~. Oivision1
Fie. '-3. Specified DiH .... ntial Oelav Accuracy tIS. Size of Meawr.
manto
Jitter
less than 0.005% (one part in 20,000) of full scale plus
0.2 os. (Wrap-around cover must be in place.)
X-y
Full Sensitivity
(CH 1Vert, CH 2Horizontal.) 5mV/div to 5V/div in
10 calibrated steps (1·2·5 sequence) accurate within 2%.
Gain can be recalibrated at front pane1.
YPerformance
Identical to CH 1. See Vertical Deflection.
X-Axis Bandwidth
DC to 4MHz (with 10 div reference signal).
x-v Phase Match (Full BWand BW Limit)
Within 3° to 4MHz.
X·Gain Match to CH 2
+15°C to +35°C: 1%
Photographic Writing Speed
At least 3div/ns for standard P31 phosphor; at least
6div/ns for optional
Pl1 phosphor (with the
TEKTRONIX C-31·R Camera and POLAROID 10,000
ASA film).
Auto Focus
Automatically maintains beam focus for all intensitY
settings. (Intensified zone and EXT Zaxis are not
auto-focused).
Graticule
Internal, no parallax. Variable edge-lighting. Markings
for measurement
of risetime. Graticule is dark with
illumination off.
Beam Finder
limits display wilhin graticule area.
External Z-Axis
Risetime 15 ns. Input R 500 n. +0.2 V {DC 10 20 MHzl
blanks trace of average intensitY.
+2 V (DC to 2MHz)
blanks maximum intensity trace.
Beam Current limit
Automatically limits the average beam current to protect
the CRT phosphor.
(limits average current to 20 fJA for
sweep rates faster than
50 ms/div; 5 fJA for 50 ms/div
and slower sweep rates and for X·Y. Backup system
shuts down power supply
if average current reaches
approximately
30 fJA.)
'-5

Specification~85/R485 Service
CALIBRATOR
Two-Frequency Fast-Rise Calibrator
ACCtJracies +15D C to +3SD C
-lSOC to +SSD
C
SVamplitude 10
0.5%
'"
1 Mn load
0.5 Vamplitude to
'"
1.5%
50 n to.5% load
50 mA amplitude to
optional
BNC acces- ,% 1.5%
sorv current loop
Selectable Frequency 0.25% 0.5%
of 1 MHz and 1kHz
Output Resistance
450 n
Risetime
Positive edge into 50 n. less than 1ns. O'JershOOl and
ringing less than
2% into 50 nat 1GHz bandwidth.
1kHz Duty Cycle
49.8% 10 50.2%
OTHER CHARACTERISTICS
Signal Outputs
Posilive gates from both time bases lapprollimately 4V).
and apositive-going Sawtooth from Time Base A
(approximately 10 V). Gates and Sawtooth are approxi-
mately
0.5 Vamplilude into 50 n.
Power Requirement
Two·position line voltage selector 115 V(90 V to
136 VI and 230 V(180 Vto 272 V) 48 to 440 Hz. 60
watts mallimum at 115 Vand 60 Hz. 0.9 Amaximum at
115 Vand
60 Hz. line fuse: 3 A fast.
Cooling
Ouiet, filtered. forced-air ventilalion. Fan speed
increases smoothly with increasing ambient temperature.
ENVIRONMENTAL CHARACTERISTICS
Ambient Temperature
Operating: _15
D
C
to +S5D C
Storage:
_3S
D
C
to +75D C
1·6
Altitude
Operating: 1015,000 feet. Maximum allowable ambient
lemperature decreased
by lD Cper 1000 feet from 5,000
10 15,000 feet.
Nonoperating: 1050,000 feet.
VibrationS
Operating: 15 minutes along each of lhe three axis,
0.025 inch peak-to·peak displacement (4 g's at 55 Hzl
1010551010 Hz in l-minute cycles.
ShockS
Operating and Nonoperaling: 30 g's, one half sine,
11·ms duralion, 2shocks per axis in each direclion for a
10tal
of 12shocks.
Electromagnetic Interference
(With 485 EMI modificalion option 41. Meets inter-
ference requirements of
Mll-1·618D: power line
conducted, 150 kHz
to 25 MHz; radiated, 150 kHz to
GHz.
Humidity
Operating and Storage: 5cycles (120 hours) to 95"
relalive humidity referenced 10 Mll-E-l6400F (par.
4.5.91hrough 4.5.9.5.1, class 41.
Dimensions and Weight
Heighl; 6and 9/16 inches.
Width: (with handleI12 inches.
Depth (including panel
coved: 18 and 1/2 inches.
Depth (handle extended): 20 and
5/8 inches.
Net weight (wilhoul accessory case
and panel coved: 21
pounds.
Net weight (with panel cover, accessory case
and
accessories): 24 pounds.
Domestic shipping weight:
31 pounds.
Export·packed weight: 42 pounds.
SR48S strapped 10 tab~, nol mounted in rloC:k.

Section 2~85/R485 Service
OPERATING INFORMATION
PRELIMINARY INFORMATION
The 485 is cooled by air entering through the air filter
on the rear panel and exiting through the holes on the sides.
Adequate clearance must be provided at these locations.
Allow at least one inch clearance behind the air filter and at
least one inch on the sides.
Athermal
cutoot in this instrument provides thermal
protection and disconnects the power
to the instrument if
the internal temperature exceeds asafe operating level.
Power is automatically restored ....... en the temperature
returns to asafe level.
Oean the air filter periodically: a
dirtY filter prevents adequate air flow into the instrument.
Operating Temperature
The 485 can be operated where the ambient air
temperature
is between -ls'"C and +5s'"C (+5°F and
+131°F). This instrument can be stored in ambient
temperatures between
-5s'"C and +75°C (-67°F and
+167"F). After storage at temperatures beyond the opera·
ting limits, allow the chassis temperature
to come within
the operating limits before power
is applied.
WARNING I
This instrument is designed for operation from a
power source with irs nautra' at or near earth
(ground) potential
with aseparate safety-earth
conductor.
It is not intended for operarion from two
phases of amulti-phase sysrem, or across the legs of a
single-phase, three-wire system.
Operating Voltage
-----,
The 485 can be operated from either a115 Vor 230 V
nominal line voltage source,
or a220 Vellternal battery
pack. The Line Voltage Selector switch on the rear panel
converts this instrument from one operating voltage to the
other.
General
To effectively use the 485, the operation and capabilities
of the instrument must be known. This section describes
the operation of the controls and connections and gives
first-time and general operating information.
CONTROLS ANO CONNECTORS
Power Cord Conductor Identification General
Conductor Color Alternate Color
Ungrounded (Line) Brown Black
Grounded (Neutral) Blue
lftfhite
Grounding (Earthlngl Green·Yellow Green·Yellow
~
This instrument may be damaged if operated with the
Line Vo/rage $elector switch
set to incorrect posi-
tions for the line volrage applied.
The major controls and connectors for operation of lhe
485 are located on the front panel of the instrument. Some
aU;l{iliary functions are provided on the side, top, bonom
and rear panel. To make full use of the capabilities of this
instrument,
the operator should be familiar with the
function and use of each of these controls and connectors.
Abrief description of each control and connector
is given
here.
Front Panel
POWER Pushbutton Turns instrument on or off.
115 V
230 V9(J.136 V
180-272 V
CAL 5 V Connector BNC connector for square·wave
voltage calibrator output signal.
The 485 is designed to be used with athree-wire AC
power system. If the three to two·wire adapter is used to
connect this instrument to atwo-wire AC power system, be
sure to connect the groond lead of the adapter to earth
(ground). Failure
to complete the groond sV1tem may allow
;he chassis of this instrument to be elevated above ground
potential and pose ashock hazard.
FREO Pushbutton
INTENSITY Control
BINTENSITY
Control
Selects one of two frequencies 11
kHz or 1 MHz) for the last-fise
calibrator signal.
Controls intensitY of writing beam.
Provides additional intensitY coo-
trol for the BSWEEP.
AEV.C,MAA.1977
2·'