Tektronix 422, Instruction Manual

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Maintenance—Type 422 AC-DC
75-watt soldering iron w ith a 1 /8-inch wide wedge-shaped
tip. Ordinary solder can be used occasionally w itho ut
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 fro n t cover fo r this instrument. Additional
solder o f 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 follow ing precautions when soldering to
ceramic terminal strips.
1. Use a hot iron fo r a short time. Apply only enough
heat to make the solder flo w 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 w ith
s o ld e r; use only enough solder to cover the wires
adequately.
5. Clean the flu x from the terminal strip w ith 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 w ith a 40- to 75-
w att 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 flo w
freely. Use a heat sink to protect heat-sensitive components.
2. A pply only enough solder to form a solid connection.
Excess solder may impair the function o f the part.
3. If a wire extends beyond the solder join t, clip o ff the
excess.
4. Clean the flu x from the solder jo in t w ith a flux-
remover solvent.
Component Replacement
WARNING
Disconnect the instrument from the power source be­
fore replacing components.
C eram ic 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 ^ S tud Pin
Fig. 4-5. Ceramic terminal strip assembly.
be re-used if they are not damaged. The applicable Tek­
tron ix Part Numbers fo r the ceramic strips and spacers used
in this instrument are given in the Mechanical Parts List.
To replace a ceramic terminal strip, use the follow ing
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 o f 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 w ith the strip, remove them
from the stud pins fo r 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 o f 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 o ff the
excess.
4. Replace all components and connections. Observe the
soldering precautions given under Soldering Techniques in
this section.
C irc u it Board Replacement. If a circuit board is
dam aged 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 fo r either the completely wired or the unwired
board. Most o f the components mounted on the circuit
4-10