Tektronix 7623, Instruction Manual

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Maintenance — 7623/R7623 Service
A good check of transistor operation is actual perfor­
mance under operating conditions. A transistor can most
effectively be checked by substituting a new component for
it (or one which has been checked previously). However, be
sure that circuit conditions are not such that a replacement
transistor might also be damaged. If substitute transistors
are not available, use a dynamic tester. Static-type testers
are not recommended, since they do not check operation
under simulated operating conditions.
E. CAPACITORS.
A leaky or shorted capacitor can best be detected by
checking resistance with an ohmmeter on the highest scale.
Do not exceed the voltage rating of the capacitor. The
resistance reading should be high after initial charge of the
capacitor. An open capacitor can best be detected with a
capacitance meter or by checking if the capacitor passes AC
signals.
Integrated circuits can be checked with a voltmeter, test
oscilloscope, or by direct substitution. A good under­
standing of the circuit operation is essential to trouble­
shooting circuits using integrated circuits. In addition,
operating waveforms, logic levels, and other operating
information for the integrated circuits are given in the
Circuit Description section. Use care when checking
voltages and waveforms around the integrated circuits so
adjacent leads are not shorted together. A convenient
means of clipping a test probe to the 14- and 16-pin
integrated circuits is with an integrated-circuit test clip.
This device also doubles as an integrated-circuit extraction
tool.
8. Repair and Readjust the Circuit. If any defective
parts are located, follow the replacement procedures given
in this section. Be sure to check the performance of any
circuit that has been repaired or that has had any electrical
components replaced.
CORRECTIVE MAINTENANCE
General
Corrective maintenance consists of component replace­
ment and instrument repair. Special techniques required to
replace components in this instrument are given here.
B. DIODES.
A diode can be checked for an open or shorted
condition by measuring the resistance between terminals.
With an ohmmeter scale having an internal source of
between 800 millivolts and 3 volts, the resistance should be
very high in one direction and very low when the meter
leads are reversed.
CAUTION
Do not use an ohmmeter scale that has a high internal
current. High currents may damage the diodes under
test.
C. RESISTORS.
Check the resistors with the ohmmeter. See the Elec­
trical Parts List for the tolerance of the resistors used in this
instrument. Resistors normally do not need to be replaced
unless the measured value varies widely from the specified
value.
D. INDUCTORS.
Check for open inductors by checking continuity with
an ohmmeter. Shorted or partially shorted inductors can
usually be found by checking the waveform response when
high-frequency signals are passed through the circuit. Partial
shorting often reduces high-frequency response (roll-off).
Obtaining Replacement Parts
Standard Parts. All electrical and mechanical part
replacements for the 7623 can be obtained through your
local TEKTRONIX Field Office or representative. However,
many of the standard electronic components can be
obtained locally in less time than is required to order them
from Tektronix, Inc. Before purchasing or ordering replace­
ment parts, check the parts list for value, tolerance, rating,
and description.
NOTE
When selecting replacement parts, it is important to
remember that the physical size and shape of a
component may affect its performance in the instru­
ment, particularly at high frequencies. All replace­
ment parts should be direct replacements unless it is
known that a different component will not adversely
affect instrument performance.
Special Parts. In addition to the standard electronic
components, some special components are used in the
7623. These components are manufactured or selected by
Tektronix, Inc. to meet specific performance requirements,
or are manufactured for Tektronix, Inc. in accordance with
our specifications. Most of the mechanical parts used in this
instrument have been manufactured by Tektronix, Inc.
Order all special parts directly from your local
TEKTRONIX Field Office or representative.
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