MODELS: LT-3280D/LT-3780D
Page 5
PRODUCT SAFETY NOTICE
Manyelectrical and mechanicalparts in televisionreceivers have specialsafety related characteristics. Thesecharacter-
istics are often not evident from visual inspection nor can the protection afforded by them necessarily be obtained by
usingreplacement components rated for highervoltage, wattage, etc.
Replacementparts which have special safety characteristics are identified in this service manual.
The replacement for any safety part should be identical in value and characteristics.
SAFETY PRECAUTIONS
NOTICE: Observe all cautions and safety related notes located inside the receiver cabinet and on the
receiverchassis.
WARNING:
1. Operationof this receiveroutsidethecabinet or with the cover removed presentsashock hazard
fromthe receiver's power supplies. Workon the receiver shouldnot be attempted byanyone who is
notthoroughlyfamiliarwiththeprecautions necessary when working on high voltage equipment.
2. Donot install, removeorhandlethe LCD panel in any manner unless shatterproofgogglesare
worn.People not soequipped should bekept away whilethe panel isbeing handled. Keep
thepanelawayfrom the body while handling.
3. Whenservice is required,observethe original lead dress. Where ashort-circuithas occurred, replace
thosecomponentsthatindicateevidenceof overheating.
Leakage current check
Beforereturning the receiver tothe customer, leakage current shouldbe measured using followingmethods.
1. Cold Check
Withthe alternating current (AC) plug removed from theAC source, place a jumper across the twoAC plug prongs.
Connect one lead of an ohm meter to theAC plug and touch the other lead to each exposed metal part (i.e. anten-
nas, handle bracket, metal cabinet, screw heads, metal overlay, control shafts, etc.), particularly any exposed metal
part that has a return path to the chassis. The resistance of the exposed metal parts having a return path to the
chassis should be a minimum of 1Meg Ohm.Any resistance below this value indicates an abnormal condition
andrequirescorrectiveaction.
2. Hot Check ...Use the circuit shown below to perform the hot check test.
1. Keep switch S1 open and connect the receiver to the measuring circuit. Immediately after
connection,and with the switching devicesofthe receiver in their operatingpositions,measure
the leakage current for both positions of switch S2.
2. Close switch S1, energizing the receiver. Immediately after closing switch S1, and with the
switchingdevices of the receiver intheiroperating positions, measure the leakagecurrentfor both
positions of switch S2. Repeat the current measurements of items 1 and 2 after the receiver has
reached thermal stabilization. The leakage current must not exceed 0.5 milliampere (mA).
