Maintenance—Type 422 AC-DC
75-watt soldering iron with a 1 /8-inch wide wedge-shaped
tip. Ordinary solder can be used occasionally without
damage 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 in the front cover for this instrument. Additional
solder of this same type should be available locally, or it
can be purchased from Tektronix, Inc. in one-pound rolls;
order by Tektronix Part No. 251-0514-00.
Observe the following precautions when soldering to
ceramic terminal strips.
1. Use a hot iron for a short time. Apply only enough
heat to make the solder flow freely. Use a heat sink to
protect heat-sensitive components.
2. Maintain a clean, properly tinned tip.
3. Avoid putting pressure on the ceramic terminal strip.
4. Do not attempt to fill the terminal-strip notch with
solder; use only enough solder to cover the wires
adequately.
5. Clean the flux from the terminal strip with a flux-
remover solvent.
Metal Terminals. When soldering metal terminals (e.g.,
switch terminals, potentiometers, etc.), ordinary 60/40
solder can be used Use a soldering iron with a 40- to 75-
watt rating and a 1 /8-inch wide wedge shaped tip.
Observe the following precautions when soldering metal
terminals:
1. Apply only enough heat to make the solder flow
freely. Use a heat sink to protect heat-sensitive components.
2. Apply only enough solder to form a solid connection.
Excess solder may impair the function of the part.
3. If a wire extends beyond the solder joint, clip off the
excess.
4. Clean the flux from the solder joint with a flux-
remover solvent.
Component Replacement
WARNING
Disconnect the instrument from the power source be
fore replacing components.
Ceramic Terminal Strip Replacement. A complete
ceramic terminal strip assembly is shown in Fig. 4-5. Re
placement strips (including studs) and spacers are supplied
under separate part numbers. However, the old spacers may
" - * - F U T n n ^ ^
Ceramic Strip
/
-Stud
Chassis Spacer ^Stud Pin
Fig. 4-5. Ceramic terminal strip assembly.
be re-used if they are not damaged. The applicable Tek
tronix Part Numbers for the ceramic strips and spacers used
in this instrument are given in the Mechanical Parts List.
To replace a ceramic terminal strip, use the following
procedure:
REMOVAL:
1. Unsolder all components and connections on the
strip. To aid in replacing the strip, it may be advisable to
mark each lead or draw a sketch to show location of the
components and connections.
2. Pry or pull the damaged strip from the chassis. Be
careful not to damage the chassis.
3. If the spacers come out with the strip, remove them
from the stud pins for use on the new strip (spacers should
be replaced if they are damaged).
REPLACEMENT:
1. Place the spacers in the chassis holes.
2. Carefully press the studs of the strip into the spacers
until they are completely seated. If necessary, use a soft
mallet and tap lightly, directly over the stud, to seat the
strip completely.
3. If the stud extends through the spacers, cut off the
excess.
4. Replace all components and connections. Observe the
soldering precautions given under Soldering Techniques in
this section.
Circuit Board Replacement. If a circuit board is
damaged beyond repair, either the entire assembly
including all soldered-on components, or the board only,
can be replaced. Part numbers are given in the Mechanical
Parts List for either the completely wired or the unwired
board. Most of the components mounted on the circuit
4-10
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