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SERVICING PRECAUTIONS
type solder removal device or with solder braid. CAUTION:Work quickly to aviod overheating the circuiboard printed foill. 6.Use the following soldering technique. a.Allow the soldering iron tip to reach a normal temperature (500k to 600k) b.First,hold the soldering iron tip and solder the strand. Against the component lead the solder melts. C.Quickly move the soldering iron tip to the junction of the compontent lead and the printed circuit foil and hold it there oniy until the solder flows onto and around both the component lead and the foil. CAUTION:work quickly to avoid overheating the circuit board printed foil. d.Closely inspect the solder area and remove any excess or splashed solder with a small wire-bristle brush. IC Remove/Replacement Some chassis circuit boards have slotted holes (oblong) through wheic the IC leads are inserted� and then bent ftat 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 parapraphs 5 and 6 above. Removal 1. Desolder and straighten each IC lead in one operation by gently prying up on the tead with soldering iron tip as the solder melts. 2.Draw away the melted solder with an anti-static suctiontype solder removal device (or with solder braid) before removing the IC. 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 wire-bristle brudh. (It is not necessary to reapply acrylic coating to the areas). �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 renaining on the circuit board. 3.Bend into a �u� shape the replacement transistor leads. 4.Connect the replacement transistor leads to the corre sponding leads extending from the circuit board and crimp the �u�with long nose pliers to insure metal to metal to metal contacttehn solder each connection. Power Output, Transistor Device Removal/Replacement 1.Heat and remove al solder from around the transistor leads. 2.Remove the heatsink 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 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 perpendiculay to the cir cuit board. 3.Observing diode polarity wrap each lead of the new diodearound the corresponding lead on the circuit board. 4.Secruely 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 stak top. 3.Solder the commections. CAUTION:Maintain original spacing between the replaced component and adjacent component and the circuit board to prevent excessive component temperaures. 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 separte fron or �liftoff� the board. The following guidelines and procedures should be followed whenever this condition is encountered. At IC Connections To repair a defective copper pattem at IC connections use the following procedure to install a jumper wire on the copper pattem side lf the circuit board.9 (use this technique ony on IC connections) 1.Carefully remove the damaged copper pattem 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 patten. 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 out-away copper patten and let it overlap the previously scraped end of the good copper pattem.Solder the overlapped area and dip off any excess jumper wire. At Other Connections Use the following technique to repir the defective copper pattem at connections other than IC pins.This technique involoves the installation of a jumper wire on the component side of the circuit board. 1.Remove the defective copper pattem with a sharp knife. Remove at least 1/4 inch of copper,to ensure that a haz ardous condition will not exist if the jumper wire opens. 2.Trace along the copper pattem from both sides of the pattem break and locate the nearest component that is directly connected to the affected copper pattem. 3. Connect insulated 20-gauge jumper wire from the lead of nearest the nearest component on one side of the pattem break to the lead of the nearest component.on the other side,Carefully crimp and solder the connections. CAUTION:Be sure the insulated jumper wire is dressed so the it does ot touch componets or sharp edges.
