Corrective Maintenance; Obtaining Replacement Parts; Soldering Techniques; General - Tektronix 453 Instruction Manual

Maintenance-Type 453/R453
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-ofn.
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 whether
the capacitor passes AC signals.
9. 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 cir-
cuit that has been repaired or that has had any electrical
components replaced.
CORRECTIVE MAINTENANCE
General
Corrective maintenance consists of component replacement
and instrument repair. Special techniques required to replace
components in this instrument are given here.
Obtaining Replacement Parts
Standard Parts. All electrical and mechanical part re-
placements for the Type 453 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 that is required to order them from
Tektronix, Inc. Before purchasing or ordering replacement
parts, check the parts lists 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
instrument, particularly at high frequencies. All
replacement 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 Type
453. 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. These special components are indicated in the
Electrical Parts List by an asterisk preceding the part number.
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 representa-
tive.
Ordering Parts. When ordering replacement parts from
Tektronix, Inc., include the following information:
1. Instrument type.
4-8
2. Instrument serial number.
3. A description of the part (if electrical, include circuit
number).
4. Tektronix Part Number.
Soldering Techniques
WARNING
Disconnect the instrument from the power source
before soldering.
Circuit Boards. Use ordinary 60/40 solder and a 35- to
40-watt pencil type soldering iron on the circuit boards.
The tip of the iron should be clean and properly tinned for
best heat transfer to the solder joint. A higher wattage
soldering iron may separate the wiring from the base
material.
The following technique should be used to replace a
component on a circuit board. Most components can be
replaced without removing the boards from the instrument.
1. Grip the component lead with long-nose pliers. Touch
the soldering iron to the lead at the solder connection. Do
not lay the iron directly on the board.
2. When the solder begins to melt, pull the lead out
gently. This should leave a clean hole in the board. If not,
the hole can be cleaned by reheating the solder and placing
a sharp object such as a toothpick into the hole to clean it
out. A vacuum-type desoldering tool can also be used for
this purpose.
3. Bend the leads of the new component to fit the holes
in the board. If the component is replaced while the board
is mounted in the instrument, cut the leads so they will just
protrude through the board. Insert the leads into the holes
in the board so the component is firmly seated against the
board (or as positioned originally). If it does not seat prop-
erly, heat the solder and gently press the component into
place.
4. Touch the iron to the connection and apply a small
amount of solder to make a firm solder joint; do not apply
too much solder. To protect heat-sensitive components, hold
the lead between the component body and the solder joint
with a pair of long nose pliers or other heat sink.
5. Clip the excess lead that protrudes through the board.
6. Clean the area around the solder connection with a
flux-remover solvent. Be careful not to remove information
printed on the board.
Ceramic Terminal Strips. Solder used on the ceramic
terminal strips should contain about 3% silver. Use a 40-
to 75-watt soldering iron with a
1 /
8
-inch wide wedge-shaped
tip. Ordinary solder can be used occasionally without dam-
age to the ceramic terminal strips. However, if ordinary
solder is used repeatedly or if excessive heat is applied,
the solder-to-ceramic bond may be broken.
A sample roll of solder containing about 3% silver is
mounted on the rear subpanel of this instrument. Additional
solder of the same type should be available locally, or it
can be purchased from Tektronix, Inc. in one-pound rolls;
order by Tektronix Pa rt No. 251-0514-00.