LOEWE PLA 5303
Instrukcja Serwisowa

CAUTION:
These servicing instructions are for use by qualified service personal only. To reduce the risk of electric shock do not perform any servicing other then that contained in the operating instructions unless you are qualified to do so:

cedure in this manual. It is recommended that the reading of the high voltage be recorded as a part of the service record. It is important to use an accurate and reliable high voltage meter. 2. This TV receiver is equipped with a Fail Safe (FS) circuit which prevents the receiver from producing an excessively high voltage even if the UB voltage increases abnormally. 3. The only source of X-RAY RADIATION in this TV receiver is the picture tube. For continued X-RAY RADIATION protection, the replacement tube must be exactly the same type tube as specified in the parts list. 4. Some part in this TV receiver have special safety-related characteristics for X-RAY RADIATION protection For continued safety, parts replacement should be undertaken only after referring to the PRODUCT SAFETY NOTICE below.

Leakage current hot check 1. Before returning the set to the customer, always perform an AC leakage current check on the exposed metallic parts of the cabinet, such as antennas, temminals, screwheads, metal overlays, control shafts etc to be sure the set is safe to operate without danger of electrical shock Plug the AC line cord directly into a 120V AC outlet (do not use a line isolation transformer during this check) Use an AC voltmeter having 5000 ohms per volt or more sensitivity in the following manner: 2. Connect a 2000 ohm 10 watt resistor, paralleled by a 0,15µF, AC type capacitor, between a known good earth ground (water pipe, conduit, etc.) and the exposed metallic parts, one at a time (Fig. 1). Measure the AC voltage across the combination of 2000 ohm resistor and 0,15µF capacitor. Reverse the AC plug at the AC outlet and repeat AC voltage measurements for each exposed metallic part. Voltage measured must not exceed 0,5 volts rms. This corresponds to 0,25 milliamp. AC. Any value exceeding this limit constitutes a potential shock hazard and must be corrected immediately.
AC leakage current hot check circuit AC Voltmeter

Note on electrostatic shielding
1. Electrostatically shielded MOS workstations Components sensitive to electrostatic discharge must be handled at workstation with electrostatic shielding. An electrostatically shielded MOS workstation is fitted with discharge resistor which earth all conductive materials, including the technician working there. Dielectrics are discharged by air ionisation. The use of soldering irons and measuring equipment at shielded workstation is only possible in conjunction with isolating transformer in each of the devices used. Measuring equipment chassis are also earthed with discharge resistors.

Safety precaution
Warning: Service should not be attempted by anyone unfamiliar with the necessary precautions on this receiver. The fol-lowing are the necessary precautions to be observed before servicing this chassis. 1. An isolation Transformer should be connected in the power line between the TV receiver and the AC line before any service is performed on the TV receiver. 2. Always discharge the picture tube anode to the CRT conductive coating before handling the picture tube. The picture tube is highly evacuated and if broken, glass fragments will be violently expelled. Use shatter proof goggles and keep picture tube away from the unprotected body while handling. 3. When replacing a chassis in the cabinet, always be certain that all the protective devices are put back in place, such as; non-metallic control knobs, insulating covers, shields, isolation resistor-capacitor network etc. 4. The regulations of the country concerned must also be observed. Leakage current cold check 1. Unplug the AC cord and connect a jumper between the two prongs of the plug. 2. Turn on the receiver's power switch. 3. Measure the resistance value with an ohmmeter, between the jumpered AC plug and each exposed metallic cabinet part on the receiver, such as screw heads, aerials, connectors, control shafts etc. When the exposed metallic part has a return path to the chassis the reading should be between 4 M� and 20 M�. When the exposed metal does not have are turn path to the chassis the reading must be infinite.

2. Shielded packaging using conductive materials To protect against electrostatic charges, electrically conductive plastics are used for packaging and transport purposes. Conductive plastics are available in the form of transparent protective bags, foam plastic, film sheeting or containers. Sensitive components requiring the use of protective packaging must only be packed and unpacked at shielded workstations.

Place this probe on each exposed metallic parts.

0,15µF

Good earth ground such as a water pipe, conduit,

Safety instructions
Warning: Before servicing this chassis, read the �X-ray radiation precaution�, �Safety precaution� and �Product safety notice� instructions below.

2000 ohm 10 watt

etc.

Fig. 1

Product safety notice
Many electrical and mechanical parts in this chassis have special safety-related characteristics. These characteristics are often passed unnoticed by a visual inspection and the protection afforded by them cannot necessarily be obtained by using replacement components rated for higher voltage, wattage. etc Replacement parts which have these special safety characteristics are identified in this manual and its supplements; electrical components having such features are identified by the international hazard symbols � � on the schematic diagram and the parts list. Before replacing any of these components, read the parts list in this manual carefully The use of substitute replacement parts which do not have the same safety characteristics as specified in the parts list may create shock fire X-ray radiation or other hazards.

X-ray radiation precaution
1. Excessive high voitage can produce potentially hazardous X-RAY RADIATION. To avoid such hazards, the high voltage must not be above the specified limit. The nominal value of the high voltage of this TV receiver is 0 kV at zero beam current (minimum brightness) under a 120V AC power source. The high voltage must not, under any circumstances, exceed � kV. Refer to table-1 for high voltage 0, � . (See Adjustments procedures on page 1-13) Each time a TV receiver requires servicing, the high voltage should be checked following the HIGH VOLTAGE CHECK pro-

1-3