Tektronix TYPE L Instruction Manual page 19

than required to obtain them from the factory.
B efore purchasing a part, be sure to consult
the Parts L ist to determine the tolerances
and rating required.
the values, tolerances, ratings, and Tektronix
part number of all components used in the
instrument.
Special Parts
In addition to the standard electronic com­
ponents mentioned in the previous paragraph,
special parts are also used. These parts are
manufactured o r selected by Tektronix to satisfy
particular requirements, or are manufactured
especially for Tektronix by other companies.
These parts, indicated by
Parts L is t, and most mechanical parts should
be ordered directly from Tektronix since they
are normally difficult or impossible to obtain
from other sources. A ll parts may be obtained
through your local Tektronix F ield Engineering
Office.
T R O U B L E S H O O T IN G
This portion of the manual w ill aid you in
troubleshooting the L Unit in the event that
trouble develops. During troubleshooting work,
the information contained in this section should
be correlated with information in other sections
o f the manual. No attempt is made to give
detailed step-by-step procedures for finding
the cause of specific troubles.
attempt is made to outline a general trouble­
shooting guide which can be used to locate
trouble which may occur in the instrument.
This guide provides a means for determining
the cause of a trouble from symptoms observed
rather than from detailed voltage or resistance
measurements.
In general, a troubleshooting procedure can
be thought of as consisting of two parts, circuit
isolation and circuit troubleshooting. The firs t
step involves isolating a trouble to a definite
part of the circuit. When the trouble has been
isolated, detailed checks can be used to d eter­
mine which part o r parts are causing the trouble.
In the following troubleshooting procedures,
it is assumed that the oscilloscope used with
the L Unit is operating correctly. This is not
always the case. Troubles occuring in the
oscilloscope can usually be detected by sub­
stituting another plug-in unit fo r the L Unit
and checking for proper operation.
AA
The Parts L ist gives
asterisks in the
Instead, an
Maintenance - Type L Plug-In
A schematic diagram of the L Unit is con­
tained in the rear
The reference designation of each component
is shown on the circuit diagram, as well as
important voltages. These should be used as
troubleshooting aids. The Circuit Description
may prove useful when troubleshooting within
a particular circuit.
Switch wafers shown on the schematic diagram
are coded to indicate the position of the wafer
on the actual switch. The number portion of
the code refers to the wafer number on the
switch assembly, wafers being numbered from
the front of the switch to the rear. The letters
F and R indicate whether the front or the rear
o f the wafer is used to perform the particular
switching function.
A ll wiring used in the L Unit is color coded
to facilitate circuit tracing. In addition,filament
and power-supply leads are distinguishable by
specific color codes. A ll power supply leads
follow the standard RETMA code.
Prelim inary Troubleshooting
Before attempting any troubleshooting work,
check all front-panel
settings. If in doubt as to the settings of
the controls, re fe r to the Operating Instructions
section. Make a careful visual check of the
instrument and the input connections. A source
o f trouble can often be detected by visual
means. If no trouble is visible, apply an input
signal and observe the CRT fo r proper wave­
shapes. Adjust the front-panel controls to see
the effect of each. The normal or abnormal
operation of each control w ill indicate what
sort of trouble is
symptoms are clearly established, the faulty
circuit can usually be isolated more readily.
Circuit failure is often caused by tube failure.
The most effective method of checking tubes
is by direct substitution
are known to be good. It is important, how­
e v e r, that these tubes be returned to the same
sockets from which they were removed unless
they are actually
replacement or switching of tubes w ill often
necessitate recalibration of the instrument.
If a defective tube is found and replaced,
but all of the trouble is not eliminated, check
the components through which the tube draws
portion of this manual.
controls for proper
encountered. Once the
with tubes which
defective. Unnecessary
4-3