DW2U
General Soldering GuidelinesRemoval
1. Use a grounded-tip, low-wattage soldering iron and1. Desolder and straighten each IC lead in one operation by
appropriate tip size and shape that will maintain tipgently prying up on the lead with the soldering iron tip as
temperature within the range 500°F to 600°F.the solder melts.
2. Use an appropriate lead free solder (see page 8). Lead2. Draw away the melted solder with an anti-static suction-
solder can be used, but there is a possibility of failure duetype solder removal device (or with solder braid) before
to insufficient strength of the solder.removing the IC.
3. Keep the soldering iron tip clean and well-tinned.Replacement
1. Carefully insert the replacement IC in the circuit board.
4. Thoroughly clean the surfaces to be soldered. Use a
small wire-bristle (0.5 inch or 1.25 cm) brush with a metal2. Carefully bend each IC lead against the circuit foil pad
handle. Do not use freon-propelled spray-on cleaners. and solder it.
5. Use the following desoldering technique.3. Clean the soldered areas with a small wire-bristle brush.
a. Allow the soldering iron tip to reach normal(It is not necessary to reapply acrylic coating to areas.)
temperature (500°F to 600°F).
Small-signal Discrete Transistor Removal/Replacement
b. Heat the component lead until the solder melts.1. Remove the defective transistor by clipping its leads as
Quickly draw away the melted solder with an anti-close as possible to the component body.
static, suction-type solder removal device or with
solder braid.2. Bend into a ?U? shape the end of each of the three leads
CAUTION: Work quickly to avoid overheating theremaining on the circuit board.
circuit board printed foil.
3. Bend into a ?U? shape the replacement transistor leads.
6. Use the following soldering technique.
a. Allow the soldering iron tip to reach normal4. Connect the replacement transistor leads to the
temperature (500°F to 600°F).corresponding leads extending from the circuit board and
crimp the ?U? with long nose pliers to insure metal to
b. First, hold the soldering iron tip and solder strandmetal contact, then solder each connection.
against the component lead until the solder melts.
Power Output Transistor Devices Removal/Replacements
c. Quickly move the soldering iron tip to the junction of1. Heat and remove all solder from around the transistor
the component lead and the printed circuit foil, andleads.
hold it there only until the solder flows onto and
around both the component lead and the foil.2. Remove the heatsink mounting screw (if so equipped).
CAUTION: Work quickly to avoid overheating the
circuit board printed foil or components.3. Carefully remove the transistor from the circuit board.
d. Closely inspect the solder area and remove any4. Insert new transistor in circuit board.
excess or splashed solder with a small wire-bristle
brush.5. Solder each transistor lead, and clip off excess lead.
6. 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.
4. Securely crimp each connection and solder it.Use Soldering Iron to Pry Leads
IC Removal/Replacement5. Inspect (on the circuit board copper side) the solder joints
Some Hitachi unitized chassis circuit boards have slottedof the two ?original leads?. If they are not shiny, reheat
holes (oblong) through which the IC leads are inserted andthem 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.
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ACEC
