DP55
IMPORTANT SAFETY INSTRUCTION
1. Before returning an instrument to the customer, always
make a safety check of the entire instrument, including
but not limited to the following items.(READING
a. Be sure that no built-in protective devices areSHOULD NOT
LEAKAGE
BE ABOVE 0.5MIU)
defective and/or have been deleted during servicing.CURRENT
(1) Protective shields are provided on this chassis toDEVICETESTER
UNDER
protect both the technician and the customer.
TEST
Correctly replace all missing protective shields,
TEST ALL
including any removed for servicing convenience. (2)EXPOSED
METAL SURFACES
When reinstalling the chassis and/or other assembly
in the cabinet, be sure to put back in place all2-WIRE CORDEARTH
GROUND
protective devices, including but not limited to,
ALSO TEST WITH PLUG
nonmetallic control knobs, insulating fishpaper,
REVERSED
adjustment and compartment covers/shields, and
(USING AC ADAPTER
isolation resistor/capacitor networks. Do not operatePLUS AS REQUIRED)
this instrument or permit it to be operated without
all protective devices correctly installed andAC Leakage Test
functioning. Servicers who defeat safety features
or fail to perform safety checks may be liable forANY MEASUREMENTS NOT WITHIN THE LIMITS
any resulting damage.SPECIFIED HEREIN INDICATE A POTENTIAL
SHOCK HAZARD THAT MUST BE ELIMINATED
b. Be sure that there are no cabinet openings throughBEFORE RETURNING THE INSTRUMENT TO THE
which an adult or child might be able to insert theirCUSTOMER OR BEFORE CONNECTING THE
fingers and contact a hazardous voltage. SuchANTENNA OR ACCESSORIES.
openings include, but are not limited to (1) spacing
between the picture tube and cabinet mask, (2)e. High Voltage � This receiver is provided with a hold
excessively wide cabinet ventilation slots, and (3) andown circuit for clearly indicating that voltage has
improperly fitted and/or incorrectly secured cabinetincreased in excess of a predetermined value.
back cover.Comply will all notes described in this Service Manual
regarding this hold down circuit when servicing, so
c. Antenna Cold Check � With the instrument AC plugthat this hold down circuit may correctly be operated.
removed from any AC source, connect an electrical
jumper across the two AC plug prongs. Place thef. Service Warning � With maximum contrast, operating
instrument AC switch in the on position. Connect onehigh voltage in this receiver is lower than 32.0 kV. In
lead of an ohmmeter to the AC plug prongs tiedcase any component having influence on high voltage
together and touch the other ohmmeter lead in turn tois replaced, confirm that the high voltage with
each tuner antenna input, exposed terminal screwmaximum contrast is lower than 32.0 kV.
and, if applicable, to the coaxial connector. If theTo measure H.V. use a high impedance H.V. meter.
measured resistance is less than 1.0 megohms orConnect (-) to chassis earth and (+) to the CRT anode
greater than 5.2 megohms, an abnormality exists thatbutton. (See the following connection diagram.)
must be corrected before the instrument is returned to
the customer. Repeat this test with the instrument ACNote: Turn power switch off without fail before the
switch in the off position.connection to the anode button is made.
d. Leakage Current Hot Check � With the instrument
completely reassembled, plug the AC line cord
directly into a 120V AC outlet. (Do not use an isolation
transformer during this test.) Use a leakage current
tester or a metering system that complies with
American National Standards Institute (ANSI) C101.0
Leakage Current for Appliances and Underwriters
Laboratories (UL) 6500, (9.1.1). With the instrument
Chassis
AC switch first in the on position and then in the off
ground
position, measure from a known earth ground (metal
waterpipe, conduit, etc.) to all exposed metal parts of
the instrument (antennas, handle bracket, metalFBT
(TH02)
cabinet, screw heads, metallic overlays, controlHigh Impedance
shafts, etc.), especially any exposed metal parts thatH.V. meterHigh voltage
connector
offer an electrical return path to the chassis. Any
Deflection P.W.B.
current measured must not exceed 0.5 MIU. Reverse
the instrument power cord plug in the outlet and
repeat test.
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ACEC
HITACHI
