Panasonic SC-TM23 Service Manual

Contents

Panasonic SC-TM23 Service Manual Manual pdf 4 page image

Disconnect AC power, discharge Power Supply Capacitors C5820 and C5840 through a 10Ω, 5W resistor to ground.DO NOT SHORT-CIRCUIT DIRECTLY (with a screwdriver blade, for instance), as this may destroy solid state devices.After repairs are completed, restore power gradually using a variac, to avoid overcurrent.Current consumption at AC 120V, 60 Hz in NO SIGNAL mode (volume min at CD mode) should be ~600mA.2 Before Repair and Adjustment3 Protection CircuitryThe protection circuitry may have operated if either of the following conditions are noticed:· No sound is heard when the power is turned on.· Sound stops during a performance.The function of this circuitry is to prevent circuitry damage if, for example, the positive and negative speaker connectionwires are“shorted”, or if speaker systems with an impedance less than the indicated rated impedance of the amplifier are used.If this occurs, follow the procedure outlines below:1.Turn off the power.2.Determine the cause of the problem and correct it.3.Turn on the power once again after one minute.Note :When the protection circuitry functions, the unit will not operate unless the power is first turned off and then on again.4 Prevention of Electro Static Discharge (ESD) to Electrostatically Sensitive (ES) DevicesSome semiconductor (solid state) devices can be damaged easily by electricity. Such components commonly are calledElectrostatically Sensitive (ES) Devices. Examples of typical ES devices are integrated circuits and some field-effecttransistorsand semiconductor “chip” components. The following techniques should be used to help reduce the incidenceof component damage caused by electro static discharge (ESD).1. Immediately before handling any semiconductor component or semiconductor-equiped assembly, drain offany ESD on your body by touching a known earth ground. Alternatively, obtain and wear a commercially availabledischarging ESD wrist strap, whichshould be removed for potential shock reasons prior to applying power to the unit undertest.2. After removing an electrical assembly equiped with ES devices, place the assembly on a conductive surfacesuch as aluminium foil, to prevent electrostatic charge build up or exposure of the assembly.3. Use only a grounded-tip soldering iron to solder or unsolder ES devices.4. Use only an anti-static solder remover device. Some solder removal devices not classified as “anti-static (ESDprotected)” can generate electrical charge to damage ES devices.5. Do not use freon-propelled chemicals. These can generate electrical charges sufficient to damage ES devices.6. Do not remove a replacement ES device from its protective package until immediately before you are readyto install it. (Most replacement ES devices are packaged with leads electrically shorted together by conductive foam,aluminium foil orcomparable conductive material).7. Immediately before removing the protective material from the leads of a replacement ES device, touch theprotective material to the chassis or circuit assembly into which the device will be installed.CautionBe sure no power is applied to the chassis or circuit, and observe all other safety precautions.8. Minimize body motions when handling unpackaged replacement ES devices. (Otherwise harmless motionsuch as the brushing together of your clothes fabric or the lifting of your foot from a carpeted floor can generate staticelectricity (ESD) sufficient todamage an ES device).IMPORTANT SAFETY NOTICEThere are special components used in this equipment which are important for safety.These parts are marked by in the schematic diagrams, Exploded Views and replacement parts list. It is essential that thesecritical parts should be replaced with manufacturer´s specified parts to prevent shock, fire, or other hazards. Do not modify theoriginal design without permission of manufacturer.4!