Hitachi 70VS810 Service Manual page 2

NOTICE: Comply with all cautions and safety-related notes
located on or inside the cabinet and on the chassis or optic unit.
WARNING: Since the chassis of this receiver is connected to
one side of the AC power supply during operation, whenever the
receiver is plugged in service should not be attempted by any-
one unfamiliar with the precautions necessary when working on
this type of receiver.
The following precautions should be observed:
1. Do not install, remove, or handle the optic unit in any manner
unless shatterproof goggles are worn. People not so equipped
should be kept away from the optic unit while handling.
2. When service is required, an isolation transformer should be
inserted between power line and the receiver before any serv-
ice is performed on a "HOT" chassis receiver.
3. When replacing a chassis in the receiver, all the protective
devices must be put back in place, such as barriers, nonmetal-
lic knobs, adjustment and compartment cover-shields, isolation
resistors, capacitors, etc.
4. When service is required, observe the original lead dress.
5. Always use the manufacturer's replacement components.
Critical components as indicated on the circuit diagram should
not be replaced by another manufacturer's. Furthermore, where
a short circuit has occurred, replace those components that
indicate evidence of overheating.
6. Before returning a serviced receiver to the customer, the serv-
ice technician must thoroughly test the unit to be certain that it
is completely safe to operate without danger of electrical shock,
and be sure that no protective device built into the receiver by
the manufacturer has become defective, or inadvertently
defeated during servicing.
Therefore, the following checks should be performed for the con-
tinued protection of the customer and service technician.
Leakage Current Cold Check
With the AC plug removed from the 120V AC 60Hz source, place
a jumper across the two plug prongs. Using an insulation tester
(DC500V), connect one lead to the jumpered AC plug and touch
the other lead to each exposed metal part (antennas, screwheads,
metal overlays, control shafts, etc.), particularly any exposed metal
part having a return path to the chassis should have a minimum
resistor reading of 2.4M
5.2M . Any resistance value below or above this range indicates
an abnormality which requires corrective action. An exposed metal
part having a return path to the chassis will indicate an open cir-
cuit.
TABLE OF CONTENTS
SAFETY PRECAUTIONS
and a maximum resistor reading of
Leakage Current Hot Check
Plug the AC line cord directly into a 120V AC 60Hz outlet (do not use
an isolated transformer for this check). Turn the AC power ON. Using
a Leakage Current Tester (Simpson's Model 228 or equivalent),
measure for current from all exposed metal parts of the cabinet
(antennas, screwheads, overlays, control shafts, etc.) particularly
any exposed metal part having a return path to the chassis or to a
known earth ground (water pipe, conduit, etc.). Any current meas-
ured must not exceed 0.5 MIU.
DEVICE
UNDER
TEST
2-WIRE CORD
ALSO TEST WITH
PLUG REVERSED (USING
AC ADAPTER PLUS
AS REQUIRED)
AC LEAKAGE TEST
ANY MEASUREMENTS NOT WITHIN THE LIMITS OUTLINED
ABOVE ARE INDICATIVE OF A POTENTIAL SHOCK HAZARD
AND MUST BE CORRECTED BEFORE RETURNING THE
RECEIVER TO THE CUSTOMER.
2
LC48/B-LC47/B/K
(READING
(READING
SHOULD NOT
SHOULD NOT
BE ABOVE
BE ABOVE
LEAKAGE
0.5 mA)
0.5 MIU)
CURRENT
TESTER
-
+
TEST ALL
EXPOSED
METAL
SURFACES
EARTH
GROUND