IC Remove/Replacement
Some chassis circuit boards have slotted holes (oblong) through which the IC leads are inserted and then bent flat against the cir- cuit 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.
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.
2.Draw away the melted solder with an
Replacement
1.Carefully insert the replacement IC in the circuit board.
2.Carefully bend each IC lead against the circuit foil pad and solder it.
3.Clean the soldered areas with a small
"Small-Signal" Discrete Transistor
Removal/Replacement
1.Remove the defective transistor by clipping its leads as close as possible to the component body.
2.Bend into a "U" shape the end of each of three leads remain- ing on the circuit board.
3.Bend into a "U" shape the replacement transistor leads.
4.Connect the replacement transistor leads to the corresponding leads extending from the circuit board and crimp the "U" with long nose pliers to insure metal to metal contact then solder each connection.
Power Output, Transistor Device
Removal/Replacement
1.Heat and remove all solder from around the transistor leads.
2.Remove the heat sink mounting screw (if so equipped).
3.Carefully remove the transistor from the heat sink of the circuit board.
4.Insert new transistor in the circuit board.
5.Solder each transistor lead, and clip off excess lead.
6.Replace heat sink.
Diode Removal/Replacement
1.Remove defective diode by clipping its leads as close as pos- sible 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.
Circuit Board Foil Repair
Excessive heat applied to the copper foil of any printed circuit board will weaken the adhesive that bonds the foil to the circuit board causing the foil to separate from or
At IC Connections
To repair a defective copper pattern at IC connections use the following procedure to install a jumper wire on the copper pattern side of the circuit board. (Use this technique only on IC connec- tions).
1.Carefully remove the damaged copper pattern with a sharp knife. (Remove only as much copper as absolutely necessary).
2.carefully scratch away the solder resist and acrylic coating (if used) from the end of the remaining copper pattern.
3.Bend a small "U" in one end of a small gauge jumper wire and carefully crimp it around the IC pin. Solder the IC connection.
4.Route the jumper wire along the path of the
At Other Connections
Use the following technique to repair the defective copper pattern at connections other than IC Pins. This technique involves the installation of a jumper wire on the component side of the circuit board.
1.Remove the defective copper pattern with a sharp knife. Remove at least 1/4 inch of copper, to ensure that a hazardous condition will not exist if the jumper wire opens.
2.Trace along the copper pattern from both sides of the pattern break and locate the nearest component that is directly con- nected to the affected copper pattern.
3.Connect insulated
Carefully crimp and solder the connections.
CAUTION: Be sure the insulated jumper wire is dressed so the it does not touch components or sharp edges.
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