IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) throughCircuit Board Foil Repair
which the IC leads are inserted and then bent flat against theExcessive heat applied to the copper foil of any printed circuit
circuit foil. When holes are the slotted type, the following techniqueboard will weaken the adhesive that bonds the foil to the circuit
should be used to remove and replace the IC. When working withboard causing the foil to separate from or "lift-off" the board. The
boards using the familiar round hole, use the standard techniquefollowing guidelines and procedures should be followed whenever
as outlined in paragraphs 5 and 6 above.this condition is encountered.
RemovalAt IC Connections
1. Desolder and straighten each IC lead in one operation by gentlyTo repair a defective copper pattern at IC connections use the
prying up on the lead with the soldering iron tip as the solderfollowing procedure to install a jumper wire on the copper pattern
melts.side of the circuit board. (Use this technique only on IC
2. Draw away the melted solder with an anti-static suction-typeconnections).
solder removal device (or with solder braid) before removing the
IC.1. Carefully remove the damaged copper pattern with a sharp
Replacementknife. (Remove only as much copper as absolutely necessary).
1. Carefully insert the replacement IC in the circuit board.2. carefully scratch away the solder resist and acrylic coating (if
2. Carefully bend each IC lead against the circuit foil pad andused) from the end of the remaining copper pattern.
solder it.3. Bend a small "U" in one end of a small gauge jumper wire and
3. Clean the soldered areas with a small wire-bristle brush.carefully crimp it around the IC pin. Solder the IC connection.
(It is not necessary to reapply acrylic coating to the areas).4. Route the jumper wire along the path of the out-away copper
pattern and let it overlap the previously scraped end of the good
"Small-Signal" Discrete Transistorcopper pattern. Solder the overlapped area and clip off any
Removal/Replacementexcess jumper wire.
1. Remove the defective transistor by clipping its leads as close as
possible to the component body.At Other Connections
2. Bend into a "U" shape the end of each of three leads remainingUse the following technique to repair the defective copper pattern
on the circuit board.at connections other than IC Pins. This technique involves the
3. Bend into a "U" shape the replacement transistor leads.installation of a jumper wire on the component side of the circuit
4. Connect the replacement transistor leads to the correspondingboard.
leads extending from the circuit board and crimp the "U" with
long nose pliers to insure metal to metal contact then solder1. Remove the defective copper pattern with a sharp knife.
each connection.Remove at least 1/4 inch of copper, to ensure that a hazardous
condition will not exist if the jumper wire opens.
Power Output, Transistor Device2. Trace along the copper pattern from both sides of the pattern
Removal/Replacementbreak and locate the nearest component that is directly
1. Heat and remove all solder from around the transistor leads.connected to the affected copper pattern.
2. Remove the heat sink mounting screw (if so equipped).3. Connect insulated 20-gauge jumper wire from the lead of the
3. Carefully remove the transistor from the heat sink of the circuitnearest component on one side of the pattern break to the lead
board.of the nearest component on the other side.
4. Insert new transistor in the circuit board.Carefully crimp and solder the connections.
5. Solder each transistor lead, and clip off excess lead.CAUTION: Be sure the insulated jumper wire is dressed so the
6. Replace heat sink.it does not touch components or sharp edges.
Diode Removal/Replacement
1. Remove defective diode by clipping its leads as close as
possible to diode body.
2. Bend the two remaining leads perpendicular y 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.
5. Inspect (on the circuit board copper side) the solder joints of
the two "original" leads. If they are not shiny, reheat them and if
necessary, apply additional solder.
Fuse and Conventional Resistor
Removal/Replacement
1. Clip each fuse or resistor lead at top of the circuit board hollow
stake.
2. Securely crimp the leads of replacement component around
notch at stake top.
3. Solder the connections.
CAUTION: Maintain original spacing between the replaced
component and adjacent components and the circuit board to
prevent excessive component temperatures.
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ACEC
