Samsung 32LE5500-SA Service Manual

Contents

Copyright LG Electronics. Inc. All right reserved.Only for training and service purposesLGE Internal Use Only- 5 -IC Remove/ReplacementSome chassis circuit boards have slotted holes (oblong) throughwhich the IC leads are inserted and then bent flat against thecircuit foil. When holes are the slotted type, the following techniqueshould be used to remove and replace the IC. When working withboards using the familiar round hole, use the standard techniqueas outlined in paragraphs 5 and 6 above.Removal1. Desolder and straighten each IC lead in one operation by gentlyprying up on the lead with the soldering iron tip as the soldermelts.2. Draw away the melted solder with an anti-static suction-typesolder removal device (or with solder braid) before removing theIC.Replacement1. Carefully insert the replacement IC in the circuit board.2. Carefully bend each IC lead against the circuit foil pad andsolder it.3. Clean the soldered areas with a small wire-bristle brush.(It is not necessary to reapply acrylic coating to the areas)."Small-Signal" Discrete TransistorRemoval/Replacement1. Remove the defective transistor by clipping its leads as close aspossible to the component body.2. Bend into a "U" shape the end of each of three leads remainingon the circuit board.3. Bend into a "U" shape the replacement transistor leads.4. Connect the replacement transistor leads to the correspondingleads extending from the circuit board and crimp the "U" withlong nose pliers to insure metal to metal contact then soldereach connection.Power Output, Transistor DeviceRemoval/Replacement1. 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 circuitboard.4. Insert new transistor in the circuit board.5. Solder each transistor lead, and clip off excess lead.6. Replace heat sink.Diode Removal/Replacement1. Remove defective diode by clipping its leads as close aspossible to diode body.2. Bend the two remaining leads perpendicular y to the circuitboard.3. Observing diode polarity, wrap each lead of the new diodearound 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 ofthe two "original" leads. If they are not shiny, reheat them and ifnecessary, apply additional solder.Fuse and Conventional ResistorRemoval/Replacement1. Clip each fuse or resistor lead at top of the circuit board hollowstake.2. Securely crimp the leads of replacement component aroundnotch at stake top.3. Solder the connections.CAUTION: Maintain original spacing between the replacedcomponent and adjacent components and the circuit board toprevent excessive component temperatures.Circuit Board Foil RepairExcessive heat applied to the copper foil of any printed circuitboard will weaken the adhesive that bonds the foil to the circuitboard causing the foil to separate from or "lift-off" the board. Thefollowing guidelines and procedures should be followed wheneverthis condition is encountered.At IC ConnectionsTo repair a defective copper pattern at IC connections use thefollowing procedure to install a jumper wire on the copper patternside of the circuit board. (Use this technique only on ICconnections).1. Carefully remove the damaged copper pattern with a sharpknife. (Remove only as much copper as absolutely necessary).2. carefully scratch away the solder resist and acrylic coating (ifused) from the end of the remaining copper pattern.3. Bend a small "U" in one end of a small gauge jumper wire andcarefully crimp it around the IC pin. Solder the IC connection.4. Route the jumper wire along the path of the out-away copperpattern and let it overlap the previously scraped end of the goodcopper pattern. Solder the overlapped area and clip off anyexcess jumper wire.At Other ConnectionsUse the following technique to repair the defective copper patternat connections other than IC Pins. This technique involves theinstallation of a jumper wire on the component side of the circuitboard.1. Remove the defective copper pattern with a sharp knife.Remove at least 1/4 inch of copper, to ensure that a hazardouscondition will not exist if the jumper wire opens.2. Trace along the copper pattern from both sides of the patternbreak and locate the nearest component that is directlyconnected to the affected copper pattern.3. Connect insulated 20-gauge jumper wire from the lead of thenearest component on one side of the pattern break to the leadof the nearest component on the other side.Carefully crimp and solder the connections.CAUTION: Be sure the insulated jumper wire is dressed so theit does not touch components or sharp edges.