PHILIPS LCD120EAA CHASSIS
Service Manual

Safety Instructions, Warnings, and Notes

LCD1.20E

2.

EN 3

2.
2.1

Safety Instructions, Warnings, and Notes
Safety Instructions
� Always connect the TV set via an Insulation transformer. Use a transformer of adequate power to protect the technician from injury by electrical shocks. It will also protect the TV set and it's components from being damaged by accidental shorts of the circuitry, which may be occurred during the service operation. � Replace safety components, indicated by the symbol i in the Schematic diagram and Replacement parts list, only by the identical components to the original ones. Any other component substitution (other than original type) may increase risk of fire or electrical shock hazard. If any fuse (or Fusible resistor) in this TV set is blown, replace it as specified. While replacing a high wattage resistor (Oxide Metal Film Resistor, over 1 W), keep the resistor 10 mm away from PCB. Keep wires away from high voltage or high temperature parts. 1. Plug the AC cord directly into the AC outlet. 2. Connect 1.5 kohm/10 W resistor in parallel with a 0.15 uF capacitor between a good known earth ground (Water Pipe, Conduit, etc.) and the exposed metallic parts. 3. Measure the AC voltage across the resistor, using the AC voltmeter with 1000 ohm/V or higher sensitivity. 4. Plug again the AC cord into the AC outlet and repeat AC voltage measurements for each exposed metallic part. Any voltage measured must not exceed 0.75 V_rms, which corresponds to 0.5 mA. 5. If any measurement is out of the specified limits, there is a possibility of a shock hazard, and the set must be checked and repaired before returning to the customer.

� �

2.2

Warnings:
Before servicing TV sets, covered by this service manual and its supplements and addenda, read and follow the Safety Instructions of this manual. Note: If unforeseen circumstances create conflict between the following Servicing Precautions and any of the Safety Instructions of this manual, always follow the Safety Instructions. Remember: Safety First.

�

2.1.1

AC Leakage Current Check Before returning the TV set to the customer, always perform an AC leakage current check on the exposed metallic parts of the cabinet, such as antennas, terminals, etc., to be sure the set is safe to operate without damage by electrical shock. Leakage Current Cold Check (Antenna Cold Check) 1. Unplug the AC cord, and connect an electrical jumper between the two plug prongs of the AC cord. 2. Turn �on� the AC power switch (keep the AC cord unplugged!). 3. Measure the resistance value between the plug prongs of the AC cord and the metal shielding of the tuner or the aerial connection of the TV set. The measured resistance should be between 1 Mohm and 5.2 Mohm. When the metal shielding has no return path to the chassis, the measured resistance must be infinite. 4. Switch the TV set �off�� and remove the electrical jumper between the two plug prongs of the AC cord. 5. Check the cabinet for defects, to prevent the possibility of the customer touching any internal parts. Leakage Current Hot Check

2.2.1

General Servicing Precautions 1. Always unplug the TV set AC power cord from the AC power source before: 1. Removing or reinstalling any component, circuit board module, or any other receiver assembly; 2. Disconnecting or reconnecting any TV set electrical plug or other electrical connection; 3. Connecting a test substitute in parallel with an electrolytic capacitor in the receiver. Caution: A wrong part substitution or incorrect polarity installation of electrolytic capacitors may result to an explosion hazard. 2. Test high voltage only by measuring it with an appropriate high voltage meter or other voltage measuring device (DVM, FETVOM, etc), equipped with a suitable high voltage probe. Do not test high voltage by "drawing an arc". 3. Do not spray chemicals on or near this TV set or any of its assemblies. 4. Unless specified otherwise in this service manual, clean electrical contacts only by applying the following mixture to the contacts with a pipe cleaner, cotton-tipped stick or comparable nonabrasive applicator; 10% (by volume) Acetone and 90% (by volume) Isopropyl alcohol (90%-99% strength). Caution: This is a flammable mixture. 5. Unless specified otherwise in this service manual, lubrication of contacts in not required. 6. Do not defeat any plug/socket B+ voltage interlocks, with which the TV sets might be equipped. 7. Do not apply AC power to this TV set and/or any of its electrical assemblies, unless all solid-state device heat sinks are correctly installed. 8. Always connect the test TV set ground lead to the TV set chassis ground before connecting the test TV set positive lead. 9. Always remove the test TV set ground lead last. 10. Use with this TV set only the test fixtures, specified in this service manual. Caution: Do not connect the test fixture ground strap to any heat sink in this TV set.

Figure 2-1 Leakage current hot check circuit Note: Do not use a line Insulation transformer during this check.