General Soldering Guidelines Removal
1. Use a grounded-tip, low-wattage soldering iron and 1. Desolder and straighten each IC lead in one operation by
appropriate tip size and shape that will maintain tip gently prying up on the lead with the soldering iron tip as
temperature within the range 500°F to 600°F. the solder melts.2. Draw away the melted solder
with an anti-static suction-type solder removal device (or
2. Use an appropriate gauge of resin-core solder composed with solder braid) before removing the IC.
of 60 parts tin/40 parts lead.
Replacement
3. Keep the soldering iron tip clean and well-tinned. 1. Carefully insert the replacement IC in the circuit board.
4. Thoroughly clean the surfaces to be soldered. Use a 2. Carefully bend each IC lead against the circuit foil pad
small wire-bristle (0.5 inch or 1.25 cm) brush with a metal and solder it.
handle. Do not use freon-propelled spray-on cleaners.
3. Clean the soldered areas with a small wire-bristle brush.
5. Use the following desoldering technique. (It is not necessary to reapply acrylic coating to areas.)
a. Allow the soldering iron tip to reach normal
temperature (500°F to 600°F). ?Small-signal? Discrete Transistor Removal/Replacement
1. Remove the defective transistor by clipping its leads as
b. Heat the component lead until the solder melts. Quickly close as possible to the component body.
draw away the melted solder with an anti-static,
suction-type solder removal device or with solder 2. Bend into a ?U? shape the end of each of three leads
braid. remaining on the circuit board.
CAUTION: Work quickly to avoid overheating the
circuit board printed foil. 3. Bend into a ?U? shape the replacement transistor leads.
6. Use the following soldering technique. 4. Connect to replacement transistor leads to the
a, Allow the soldering iron tip to reach normal corresponding leads extending from the circuit board and
temperature (500°F to 600°F). crimp the ?U? with long nose pliers to insure metal to
metal contact, then solder each connection.
b. First, hold the soldering iron tip and solder strand
against the component lead until the solder melts. Power Output Transistor Devices Removal/Replacements
Heat and remove all solder from around the transistor
c. Quickly move the soldering iron tip to the junction of leads.
the component lead and the printed circuit foil, and
hold it there only until the solder flows onto and Remove the heatsink mounting screw (if so equipped).
around both the component lead and the foil.
CAUTION: Work quickly to avoid overheating the Carefully remove the transistor from the circuit board.
circuit board printed foil or components.
Insert new transistor in circuit board.
d. Closely inspect the solder area and remove any excess
or splashed solder with a small wire-bristle brush. Solder each transistor lead, and clip off excess lead.
Y. Replace heatsink.
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as
possible to diode body.
2. Bend the two remaining leads perpendicularly to the
circuit board.
3. Observing diode polarity, wrap each lead of the new
diode around the corresponding lead on the circuit board.
Use Solding Iron to Pry Leads
4. Securely crimp each connection and solder it.
IC Removal/Replacement 5. Inspect (on the circuit board copper side) the solder joints
Some Hitachi unitized chassis circuit boards have slotted of the two ?original leads?. If they are not shiny, reheat
holes (oblong) through which the IC leads are inserted and them and, if necessary, apply additional solder.
then bent flat against the circuit foil. When holes are the
slotted type, the following technique should be used to
remove and replace the IC. When working with boards using
the familiar round hole, use the standard technique as
outlined in paragraphs 5 and 6 above. |