Philips 29PFL4508/F4 Service Manual page 6

4. Hot Chassis Warning -
a. Some TV receiver chassis are electrically
connected directly to one conductor of the AC
power cord and maybe safety-serviced without
an isolation transformer only if the AC power
plug is inserted so that the chassis is
connected to the ground side of the AC power
source. To confirm that the AC power plug is
inserted correctly, with an AC voltmeter,
measure between the chassis and a known
earth ground. If a voltage reading in excess of
1.0 V is obtained, remove and reinsert the AC
power plug in the opposite polarity and again
measure the voltage potential between the
chassis and a known earth ground.
b. Some TV receiver chassis normally have 85V
AC(RMS) between chassis and earth ground
regardless of the AC plug polarity. This chassis
can be safety-serviced only with an isolation
transformer inserted in the power line between
the receiver and the AC power source, for both
personnel and test equipment protection.
c. Some TV receiver chassis have a secondary
ground system in addition to the main chassis
ground. This secondary ground system is not
isolated from the AC power line. The two
ground systems are electrically separated by
insulation material that must not be defeated or
altered.
5. Observe original lead dress. Take extra care to
assure correct lead dress in the following areas: a.
near sharp edges, b. near thermally hot parts-be
sure that leads and components do not touch
thermally hot parts, c. the AC supply, d. high
voltage, and, e. antenna wiring. Always inspect in
all areas for pinched, out of place, or frayed wiring.
Check AC power cord for damage.
6. Components, parts, and/or wiring that appear to
have overheated or are otherwise damaged
should be replaced with components, parts, or
wiring that meet original specifications.
Additionally, determine the cause of overheating
and/or damage and, if necessary, take corrective
action to remove any potential safety hazard.
7. Product Safety Notice - Some electrical and
mechanical parts have special safety-related
characteristics which are often not evident from
visual inspection, nor can the protection they give
necessarily be obtained by replacing them with
components rated for higher voltage, wattage, etc..
Parts that have special safety characteristics are
identified by a # on schematics and in parts lists.
Use of a substitute replacement that does not
have the same safety characteristics as the
recommended replacement part might create
shock, fire, and/or other hazards. The product's
safety is under review continuously and new
instructions are issued whenever appropriate.
Prior to shipment from the factory, our products
are strictly inspected to confirm they comply with
the recognized product safety and electrical codes
of the countries in which they are to be sold.
However, in order to maintain such compliance, it
is equally important to implement the following
precautions when a set is being serviced.
2-2 LTVP_ISP