M7LXU
SAFETY PRECAUTIONS
Leakage Current Hot Check
NOTICE: Comply with all cautions and safety related notes
located on or inside the cabinet and on the chassis or pic-
Plug the AC line cord directly into an AC 120V 60Hz outlet
ture tube.
(do not use an isolation transformer for this check). Turn
the AC power ON. Using a ?leakage Current Tester
WARNING: Since the chassis of this receiver is connected
(Simpson?s Model 229 or equivalent)?, measure for current
to one side of the AC power supply during operation, when-
from all exposed metal parts of the cabinet (antennas,
ever the receiver is plugged in, service should not be at-
screwheads, overlays, control shafts, etc.) particularly any
tempted by anyone unfamiliar with the precautions neces-
exposed metal part having a return path to the chassis or
sary when working on this type of receiver.
to a known earth ground (water pipe, conduit, etc.). Any
current measured must not exceed 0.5mA.
The following precautions should be observed:
1. Do not install, remove, or handle the picture tube in any
manner unless shatterproof goggles are worn. People
not so equipped should be kept away from the picture
tube while handling. (READING
SHOULD NOT
0
m BE ABOVE
2. When service is required, an isolation transformer should LEAKAGE 0.5mA)
DEVICE
be inserted between power line and the receiver before CURRENT
UNDER ?,TESTER J
any service is performed on a ?HOT? chassis receiver.
TEST ?f -
I
TEST ALL
3. When replacing a chassis in the receiver, all the protec-
EXPOSED METAL
tive devices must be put back in place, such as barri-
SURFACES
ers, nonmetallic knobs, adjustment and compartment
cover-shields, isolation resistors, capacitors, etc. 2-WIRE CORD
4. When service is required, observe the original lead dress ALSO TEST WITH 6 d
in the high voltage circuitry area. PLUG REVERSED EARTH
(USING AC ADAPTER 4 GROUND
PLUG AS REQUIRED)
5. Always use the manufacturer?s replacement compo-
nents. Critical components as indicated on the circuit
diagram should not be replaced by another
manufacturer?s, Furthermore, where a short circuit has AC LEAKAGE TEST
occurred, replace those components that indicate evi-
dence of overheating.
ANY MEASUREMENTS NOT WITHIN THE LIMITS OUT-
6. Before returning a serviced receiver to the customer, the LINED ABOVE ARE INDICATIVE OF A POTENTIAL
service technician must thoroughly test the unit to be SHOCK HAZARD AND MUST BE CORRECTED BEFORE
certain that it is completely safe to operate without dan- RETURNING THE RECEIVER TO THE CUSTOMER.
ger of electrical shock, and be sure that no protective
device built into the receiver by the manufacturer has High Voltage
become defective, or inadvertently defeated during ser- This receiver is provided with a hold down circuit for clearly
vicing.
indicating that voltage has increased in excess of a prede-
termined value. Comply with all notes described in this
Therefore, the following checks should be performed for Service Manual regarding this hold down circuit when ser-
the continued protection of the customer and service tech-
vicing, so that this hold down circuit is operated correctly.
nician.
Serviceman Warning
Leakage Current Cold Check With minimum BRIGHTNESS and CONTRAST, the operat-
With the AC plug removed from the 12OV AC 60Hz source, ing high voltage in this receiver is lower than 35.0kV. Ir,
place a jumper across the two plug prongs. Turn the AC case any component having influence on the high voltage
power switch ON using an insulation tester (DC500V), con- is replaced, confirm that high voltage with minimum BRIGHT
nect one lead to the jumpered AC plug and touch the other NESS and CONTRAST is lower than 350kV. To measure
lead to each exposed metal part (antennas, screwheads, high voltage use a high impedance High Voltage Meter.
metal overlays, control shafts, etc.), particularly any exposed Connect (-) to chassis earth and (+) to the CPT Anode but-
metal part having a return path to the chassis should have ton (See the following connection diagram).
a minimum resistor reading of 0.24MQ and a maximum re-
sistor reading of 5.2MQ Any resistance value below or
NOTE: Turn the power switch OFF without fail before the
above this range indicates an abnormality which requires
connection to the Anode button is made.
corrective action. Exposed metal part not having a return
path to the chassis will indicate an open circuit.
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ACEC
