LG-FFH818A-cs-sp 维修电路原理图.pdf
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1、4SERVICING PRECAUTIONSNOTES REGARDING HANDLING OF THE PICK-UP1. Notes for transport and storage1) The pick-up should always be left in its conductive bag until immediately prior to use.2) The pick-up should never be subjected to external pressure or impact.2. Repair notes1) The pick-up incorporates
2、a strong magnet, and so should never be brought close to magnetic materials.2) The pick-up should always be handled correctly and carefully, taking care to avoid external pressure andimpact. If it is subjected to strong pressure or impact, the result may be an operational malfunction and/ordamage to
3、 the printed-circuit board.3) Each and every pick-up is already individually adjusted to a high degree of precision, and for that reasonthe adjustment point and installation screws should absolutely never be touched.4) Laser beams may damage the eyes!Absolutely never permit laser beams to enter the
4、eyes!Also NEVER switch ON the power to the laser output part (lens, etc.) of the pick-up if it is damaged.5) Cleaning the lens surfaceIf there is dust on the lens surface, the dust should be cleaned away by using an air bush (such as usedfor camera lens). The lens is held by a delicate spring. When
5、cleaning the lens surface, therefore, acotton swab should be used, taking care not to distort this.6) Never attempt to disassemble the pick-up.Spring by excess pressure. If the lens is extremely dirty, apply isopropyl alcohol to the cotton swab. (Donot use any other liquid cleaners, because they wil
6、l damage the lens.) Take care not to use too much ofthis alcohol on the swab, and do not allow the alcohol to get inside the pick-up.Storage in conductive bagDrop impactNEVER look directly at the laser beam, and don t letcontact fingers or other exposed skin.MagnetHow to hold the pick-upPressurePres
7、sureCotton swabConductive SheetRadioFans.CN 收音机爱 好者资料库5NOTES REGARDING COMPACT DISC PLAYER REPAIRS 1. Preparations1) Compact disc players incorporate a great many ICs as well as the pick-up (laser diode). Thesecomponents are sensitive to, and easily affected by, static electricity. If such static el
8、ectricity is highvoltage, components can be damaged, and for that reason components should be handled with care.2) The pick-up is composed of many optical components and other high-precision components. Care mustbe taken, therefore, to avoid repair or storage where the temperature of humidity is hig
9、h, where strongmagnetism is present, or where there is excessive dust.2. Notes for repair1) Before replacing a component part, first disconnect the power supply lead wire from the unit2) All equipment, measuring instruments and tools must be grounded.3) The workbench should be covered with a conduct
10、ive sheet and grounded.When removing the laser pick-up from its conductive bag, do not place the pick-up on the bag. (This isbecause there is the possibility of damage by static electricity.)4) To prevent AC leakage, the metal part of the soldering iron should be grounded.5) Workers should be ground
11、ed by an armband (1M)6) Care should be taken not to permit the laser pick-up to come in contact with clothing, in order to preventstatic electricity changes in the clothing to escape from the armband.7) The laser beam from the pick-up should NEVER be directly facing the eyes or bare skin.ArmbandCond
12、uctiveSheetResistor(1 Mohm)Resistor(1 Mohm)CAUTIONRadioFans.CN 收音机爱 好者资料库6ESD PRECAUTIONSElectrostatically Sensitive Devices (ESD)Some semiconductor (solid state) devices can be damaged easily by static electricity. Such componentscommonly are called Electrostatically Sensitive Devices (ESD). Exampl
13、es of typical ESD devices are integratedcircuits and some field-effect transistors and semiconductor chip components. The following techniques shouldbe used to help reduce the incidence of component damage caused by static electricity.1. Immediately before handling any semiconductor component or sem
14、iconductor-equipped assembly, drain offany electrostatic charge on your body by touching a known earth ground. Alternatively, obtain and wear acommercially available discharging wrist strap device, which should be removed for potential shock reasonsprior to applying power to the unit under test.2. A
15、fter removing an electrical assembly equipped with ESD devices, place the assembly on a conductivesurface such as aluminum foil, to prevent electrostatic charge buildup or exposure of the assembly.3. Use only a grounded-tip soldering iron to solder or unsolder ESD devices.4. Use only an anti-static
16、solder removal device. Some solder removal devices not classified as anti-static cangenerate electrical charges sufficient to damage ESD devices.5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ESDdevices.6. Do not remove a replacement ESD device fr
17、om its protective package until immediately before you areready to install it. (Most replacement ESD devices are packaged with leads electrically shorted together byconductive foam, aluminum foil or comparable conductive materials).7. Immediately before removing the protective material from the lead
18、s of a replacement ESD device, touch theprotective material to the chassis or circuit assembly into which the device will by installed.CAUTION : BE SURE NO POWER IS APPLIED TO THE CHASSIS OR CIRCUIT, AND OBSERVE ALL OTHERSAFETY PRECAUTIONS.8. Minimize bodily motions when handing unpackaged replaceme
19、nt ESD devices. (Otherwise harmless motionsuch as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor cangenerate static electricity sufficient to damage an ESD device).ADJUSTMENTSThis set has been aligned at the factory and normally will not require furthe
20、r adjustment. As a result, it is notrecommended that any attempt is made to modificate any circuit. If any parts are replaced or if anyone tamperswith the adjustment, realignment may be necessary.IMPORTANT1. Check Power-source voltage.2. Set the function switch to band being aligned.3. Turn volume c
21、ontrol to minimum unless otherwise noted.4. Connect low side of signal source and output indicator to chassis ground unless otherwise specified.5. Keep the signal input as low as possible to avoid AGC and AC action.TEST & ADJUSTMENT POINTFigure 1. Main P.C. Board(FFH-717)- 8 -VR201(Adjustment Point)
22、L203(Rec Bias)L105(LW/SW USABLESENSITIVITY)L016(DC VOLTAGE)L017(MW USABLESENSITIVITY)TAPE DECK ADJUSTMENT1. AZIMUTH ADJUSTMENTFigure 3. Azimuth Adjustment Connection DiagramCH1 CH2Speaker OutPlayback ModeHeadTest TapeMTT-114L chR chGNDDual-tracesynchroscopeElectronicVoltmeterL outR outUnitFigure 2.
23、Main P.C. Board(FFH-818)Deck ModeTest TapeTest PointAdjustmentAdjust forA Deck PlaybackMTT-114Speaker OutDECK ScrewMaximumAzimuth ScrewB Deck PlaybackMTT-114Speaker OutAzimuth ScrewMaximumVR201(Adjustment Point)L203(Rec Bias)L105(LW/SW USABLESENSITIVITY)L016(DC VOLTAGE)L017(MW USABLE SENSITIVITY)- 9
24、 - 10 -3. RECORD BIAS ADJUSTMENTHeadUnitPN202GNDRecord/PlaybackheadTest TapeMTT-5511Record/Playbackand Pause ModeFrequency CounterDeck ModeTest TapeTest PointAdjustmentAdjust forRec/PauseMTT-5511ERASE HEADL20385kHz5kHzWIRE(PN202)Figure 5. Record Bias Adjustment Connection Diagram4. TUNER ADJUSTMENTF
25、igure 6. Tuner(S curve) Adjustment Connection DiagramUnitSignal GeneratorGNDElectronicOSCILLOSCOPEFM AntennaTerminalSpeakeItemTest PointAdjustmentAdjust forDC VoltageChecker PinL1060V50mVMW UsableSpeaker OutL107MaximumSensitivityLW/SW UsableSpeaker OutL105MaximumSensitivity2. MOTOR SPEED ADJUSTMENTF
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