Tektronix 455, Instruction Manual, Page: 86 / 246

Maintenance—4 5 5 /A 2 /B 2
TROUBLESHOOTING
The following information is provided to facilitate troubleshooting. Information contained in other sections o f this manual
should be used along with the following to aid in locating the defective component. An understanding o f the circuit opera­
tion is helpful in locating troubles, particularly where integrated circuits are used. See the Circuit Description for this infor­
mation.
TRO UBLESHO O TING AIDS
Troubleshooting Chart
A troubleshooting chart (Fig. 5-13) is provided to aid in
locating problem areas.
Diagrams
Complete circuit diagrams are given on foldout pages in the
Diagrams sections. The portions of the circuit mounted on
circuit boards are enclosed w ith heavy lines. The compo­
nent number and electrical value of each component in this
instrument are shown on the diagrams (see the first page of
the Diagrams section for definition of the reference desig­
nators used to identify components). Each main circuit is
assigned a series of component numbers to assist in identify­
ing their circuit location. Im portant voltages and waveforms
are also shown on the diagrams. The physical locations of
the waveform test points are shown on the circuit-board
illustrations.
Circuit Board Illustrations
In conjunction w ith each circuit diagram is a circuit board
illustration. These are located on the back of the pullout
page opposite the associated circu it diagram. Each circuit
component shown on the circu it diagram is identified on
the circuit board illustration by its circuit number. Circuit
number locations are identified w ith a grid-index system.
Component Value Identification
Values of capacitors, diodes and resistors used in this instru­
ment are identified by direct numerical values or by a color-
code scheme. Fig. 5-12 shows the color-code and numer­
ical-value schemes used.
Semiconductor Lead Configurations
Typical semiconductor lead configurations are shown at the
beginning of the diagrams section.
TROUBLESHOOTING EQUIPM ENT
The following equipment is useful for troubleshooting.
1. Semiconductor Tester
Description: Dynamic-type tester. Must be capable of
measuring reverse breakdown voltages of at least 400
volts.
Purpose: To test semiconductors.
Example: Tektronix 576 Curve Tracer or Tektronix 577
(D 1 or D2) Curve Tracer with 177 Test Fixture.
2. Test Oscilloscope
Description: Frequency response, dc to at least 50
megahertz; deflection factor, 5 m illivolts to 5 volts/
division; Input impedance, 1 megohm, 20 picofarads;
sweep rate, 0.5 second/division to 0.05 microsecond/
division. A 10X, 10 megohm voltage probe should be
used to reduce circuit loading fo r voltage measurements.
Purpose: To check operating waveforms.
3. Multimeter
Description: Non-loading digital multimeter. Voltmeter,
10 megohm input impedance and 0 to 150 volts range;
dc voltage accuracy, w ithin 0.15%; display,
4'A
digits.
Ohmmeter, 0 to 20 megohms.
Purpose: To check voltages and fo r general trouble­
shooting.
4. Variable Autotransformer
Description: Output variable from 0 to 140 volts, 1.2
amperes minimum rating. Must have a 3-wire power cord,
plug and receptacle.
Purpose: To vary the input line voltage when trouble­
shooting in the power supply.
5-14
REV. A, OCT 1975