Before Repair And Adjustment; Protection Circuitry; Prevention Of Electrostatic Discharge (Esd) To Electrostatically Sensitive (Es) Devices - Panasonic SA-PM53E Service Manual

1.3. Before Repair and Adjustment

Disconnect AC power, discharge Power Supply Capacitors C512, C513, C514, C606, C608, C610, C624
through a 10 , 1W 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 230V, 50 Hz in NO SIGNAL mode should be
~300 mA (E/EG).
- Current consumption at AC 230V-240V, 50 Hz in NO SIGNAL mode
should be ~300 mA (EB).

1.4. Protection Circuitry

The 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 connection wires 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.
2. Prevention of Electro Static Discharge (ESD) to
Electrostatically Sensitive (ES) Devices
Some semiconductor (solid state) devices can be damaged easily by electricity. Such components
commonly are called Electrostatically Sensitive (ES) Devices. Examples of typical ES devices are
integrated circuits and some field-effect transistors and semiconductor "chip" components. The
following techniques should be used to help reduce the incidence of component damage caused by
electro static discharge (ESD).
1. Immediately before handling any semiconductor component or
semiconductor-equiped assembly, drain off any ESD on your body by
touching a known earth ground. Alternatively, obtain and wear a
commercially available discharging ESD wrist strap, which should be
removed for potential shock reasons prior to applying power to the unit
under test.
2. After removing an electrical assembly equiped with ES devices, place
the assembly on a conductive surface such as aluminium foil, to
prevent electrostatic charge build up or exposure of the assembly.
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