General Soldering Guidelines2. Draw away the melted solder with an anti-static suction-type
1. Use a grounded-tip, low-wattage soldering iron and appropri-solder removal device (or with solder braid) before removing
ate tip size and shape that will maintain tip temperature with-the IC.
in the range 500!F to 600!F.
Replacement
2. Use an appropriate gauge of resin-core solder composed of1. Carefully insert the replacement IC in the circuit board.
60 parts tin/40 parts lead.
2. Carefully bend each IC lead against the circuit foil pad and
3. Keep the soldering iron tip clean and well-tinned.solder it.
4. Thoroughly clean the surfaces to be soldered. Use a small3. Clean the soldered areas with a small wire-bristle brush. (It is
wire-bristle (0.5 inch or 1.25 cm) brush with a metal handle.not necessary to reapply acrylic coating to areas.)
Do not use freon-propelled spray-on cleaners.
OSmall-signal� Discrete Transistor Removal/Replacement
5. Use the following desoldering technique.1. Remove the defective transistor by clipping its leads as close
a. Allow the soldering iron tip to reach normal temperature as possible to the component body.
(500!F to 600!F).
2. Bend into a OU� shape the end of each of three leads remain-
b. Heat the component lead until the solder melts. Quicklying on the circuit board.
draw away the melted solder with an anti-static, suction-
type solder removal device or with solder braid.3. Bend into a OU� shape the replacement transistor leads.
CAUTION: Work quickly to avoid overheating the circuit
board printed foil.4. Connect to replacement transistor leads to the corresponding
leads extending from the circuit board and crimp the OU� with
6. Use the following soldering technique.long nose pliers to insure metal to metal contact, then solder
a. Allow the sodering iron tip to reach normal temperature each connection.
(500!F to 600!F).
Power Output Transistor Devices Removal/Replacement
b. First, hold the soldering iron tip and solder strand against1. Heat and remove all solder from around the transistor leads.
the component lead until the solder melts.
2. Remove the heatsink mounting screw (if so equipped).
c. Quickly move the soldering iron tip to the junction of the
component lead and the printed circuit foil, and hold it3. Carefully remove the transistor from the circuit board.
there only until the solder flows onto and around both the
component lead and the foil.4. Insert new transistor in circuit board.
CAUTION: Work quickly to avoid overheating the circuit
board printed foil or components.5. Solder each transistor lead, and clip off excess lead.
d. Closely inspect the solder area and remove any excess6. Replace heatsink.
or splashed solder with a small wire-bristle brush.
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as
possilbe 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 of
Some Hitachi unitized chassis circuit boards have slotted holesthe two Ooriginal leads�. If they are not shiny, reheat them
(oblong) through which the IC leads are inserted and then bent flatand, if necessary, apply additional solder.
against the circuit foil. When holes are the slotted type, the fol-
lowing 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.
Removal
1. Desolder and straighten each IC lead in one operation by
gently prying up on the lead with the soldering iron tip as the
solder melts.
5
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