Tektronix 502 series, Instruction Manual

Page: 40 / 114

TROUBLESHOOTING
GENERAL IN FO R M A TIO N
This section is included to provide you with
information about the Type 502 Oscilloscope that
will enable you to more efficiently troubleshoot
the instrument in the event of equipment failure.
During troubleshooting work, you should cor­
relate information contained in this section with
information obtained from other sections of this
manual. We have not attempted to give de­
tailed step by step procedures for finding the
cause of specific troubles, but rather have at­
tempted to outline a general troubleshooting
guide. This guide provides a means for deter­
mining the probable defective circuit or part
from the symptoms observed rather than from
detailed voltage or resistance measurements.
Although the Type 502 Oscilloscope is a com­
plex instrument, it can conveniently be thought
of as consisting of a number of interrelated basic
circuits as shown on the block diagram contained
in the diagram section of the manual. Each of
these basic circuits performs a specific part of
the overall circuit operation required to place a
display on the face of the crt. If any one of
these circuits should fail, a definite symptom of
this failure will be apparent. By investigating
the possible causes of this symptom by means of
systemized circuit checks, it is possible to deter­
mine which circuit or circuits are at fault. After
determining which circuit is defective, additional
checks will allow you to isolate the trouble to
a particular part.
Before proceeding with troubleshooting of the
instrument, make sure that any apparent trouble
is actually due to a malfunction within the oscil­
loscope, and not due to improper control set­
tings. Instructions for the operation of the instru­
ment are contained in the “ Operating instruc­
tions” section of this manual. If, after reviewing
the Operating Instructions, you determine that
control settings are not at fault, you should next
check the calibration of the suspected circuit
according to the procedures contained in the
“ Recalibration Procedure” section of the manual.
A calibration check will not only correct any
troubles due to improper calibration, but will
often also aid in isolating the faulty stage in
cases where an actual trouble does exist. After
checking control settings and calibration, if the
trouble still exists, you should then go to a more
detailed
troubleshooting analysis. Specific
troubleshooting procedures are given later in this
section.
Separate schematic diagrams of each circuit
are contained in the rear portion of this manual
together with a block diagram which provides
an overall picture of instrument operation. The
reference designation of each electronic com­
ponent of the instrument is shown on the circuit
diagrams as well as important voltages and
waveforms. The following chart lists the refer­
ence designations associated with each circuit.
All numbers............... Time-Base Trigger
less than 100
100 series............Time-Base Generator
and Timing Switch
300 series............Horizontal Amplifier
400 series................... Upper and Lower
Beam Vertical
Amplifiers
600 and 700 series..........Low Voltage
Power Supply
800 series...........................CRT Circuits
and Calibrator
Switch wafers shown on the schematic dia­
grams are coded to indicate the position of the
wafer on the actual switches. The number por­
tion of the code refers to the wafer number on
the switch assembly, wafers being numbered
from the front of the switch to the rear, and the
letters F and R indicate whether the front or the
rear of the wafer is used to perform the partic­
ular switching function. Photographic details of
these switches are also shown on the same fold-
out page as the corresponding schematic dia­
gram. These photographs are provided as parts
location guides.
All wiring used in the Type 502 Oscilloscope
is color coded to facilitate circuit tracing. In ad­
dition, primary power, filament, and regulated
power supply output leads are distinguished by
specific color codes. All regulated power supply
output leads follow the standard RETMA code.
The —150 volt bus wire is coded brown-green-
brown; the +100 volt bus is coded brown-black-
brown; and the +350 volt bus is coded orange-
green-brown. The widest stripe identifies the first
color of the code.
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5 -4
MAINTENANCE — TYPE 502