Go to cover page
TELEVISION/MONITOR SAFETY GUIDELINES FOR THE PROFESSIONAL SERVICE TECHNICIAN
Safety Checks
After the original swevice problem has been corrected,a complete safety
check
6. New picture tubes are specifically designed to withstand higher operathng
should be made. Be sure to check over the entire set, not just the areas
voltages without creating undesirable X-radiation. It is strongly
where you have worked. Some previous servicer may have left an unsaferecommended that any shop test fixture which is to be used with the new
condition,which could be unknowingly passed on to your customer. Be sure
higher voltage chassis be equipped with one of the new type tubes
to check all of the following:
designed for this service.Addition of a permanently connected HV meter
to the shop test fixture is advisable. The CRT types used in these new
Fire and Shock H azard
sets should never be replaced with any other types,as this may result in
1. Be sure all components are positioned in such a way as to avoid the
excessive X-radiation.
possibility of adjacent component shorts. This is especially important
7. It is essential to use the specified picture tube to avoid a possible X-diation
on those chassis which are transported to and feom the service shop.
2. Never release a repaired unit unless all protective devices such asproblem.
8. Most TV receivers contain some type of emergency "Hold Down" circuit to
insulators, barries, covers, strain reliefs, and other hardware have been
pervent HV from rising to excessive levels in the presence of a failure
installed in accordance with the original design.
mode. These various circuits should be understood by all technicians
3. Soldering and wiring must be inspected to locate possible cold solder
servicing them, especially since many hold down circuits are inoperative
joints,solder splashes,sharp solder points, frayed leads, pinched leads,
as long as the receiver performs normally.
or damaged insulation ( including the ac cord).Be certain to remove
loose solder balls and all other loose foreign particles.
Leakage Current Cold Check
4. Check across-the-line components and other components for physical
1. Unplug the ac line cord and connect a jumper between the two prongs of
evidence of damage or deteriortion and replace if necessary. Follow
the plug.
original layout,lead length, and dress.
2. Turn on the power switch.
5. No lead or component should touch a receiving tube or a resistor rated
3. Measure the resistance value between the jumpered ac plug and all
at 1 watt or more. Lead tension around protruding metal surfaces or
exposed cabinet parts of the receiver, such as screw heads, antennas,
edges must be avoided.
and control shafts.When the exposed metallic part has a return path to
6. Critical components having special safety characteristics are identified
the chassis, the reading should be between 1 megohm and 5.2 megohms.
with ans bythe Ref. No. in the parts list and enclosed within a broken line
When the exposed metal does not have a return path to thr chassis, the
* (where seceral criticalcomponents are grouped in one area) along with
reading must be infinity.Remove the jumper from the ac line cord.
the safety symbols on the schematic diagrams and/or exploded views.
7. When servicing any unit, always use a seoparate isolation transformer
for the chassis Failure to use a separate isolation transformer may
exopose you to possible shock hazard, and may cause damage to
servicing instruments.
8. Many electronic products use a polarized ac line cord (one wide pin on
the plug.) Defeating this safety feature may create a potential hazard to
the service and the user. Extension cords which do not incorporate the
TO0.15 uF
polarizing feature should never be used.WATER
9. After reassembly of the unit, always perform an leakage test or resistancePIPEINSTRUMENTS
test from the line cord to all exposed metal parts of the cabinet. Also checkEARTHEXPOSED
all metal control shafts(with knobs removed), antenna terminals, handles,METAL PARTS
1500 ohm, 10WGROUND
screws, etc. to be sure the unit may be safety operted without danger of
electrical shock.
Leakage Current Hot Check
1. Do not use an isolation transformer for this test. Plug the completely
* Broken line
reassembled receiver directly into the ac outlet.
2. Connect a 1.5k, 10w resistor paralleled by a 0.15uf. capacitor between
Implosion
each exposed metallic cabinet part and a good earth ground such as a
1. All picture tubes used in current model receivers are equipped with an
water pipe, as shown above.
intergral implosion system. Care should always be used, and safety
3. Use an ac voltmeter with at least 5000 ohmsy volt sensitivity to measure
glassesworn,whenever handling any picture tube. Avoid scratching or
the potential across the resistor.
other rwise damaging the picture tube during installation.
4. The potential at any point should not exceed 0.75 volts. A leakage current
2. Use only replacement tubes specified by the manufacturer.
tester may be used to make this test; leakage current must not exceed
0.5 milliamps. If a measutement is outside of the specified limits, there is
X-radiation
a possibility of shock hazard. The receiver should be repaired and
1. Be sure procedures and instructions to all your service personnel cover
the subject of X-radiation. Potential sources of X-rays in TV receivers arerechecked before retutning it to the customer.
5. Repeat the above procedure with the ac plug reversed.( Note: An ac
the picture tube and the high voltage circuits. The basic precaution which
adapter is necessary when a polarized plug is used. Do not defeat the
must be exercised is to keep the high voltage at the factory recommended
polarizing feature of the plug.)
level.
2. To avoid possible exposure to X-radiation and electrical shock, only the
Picture Tube Replacement
manufacturer's specified anode connectors must be used.
The primary source of X-radiation in this television receiver is the picture
3. It is essential that the service technician has an accurate HV meter
tube.The picturetube utilized in this chassis is specially constructed to limit
available at all times. The calibration of this meter should be checked
X-radiation emissions. For continued X-radiation protection, the replacement
periodically against a reference standard.
tube must be the same type as the original, including suffix letter,or a Philips
4. When the HV circuitry isoperating properly there is no possibility of an x-
approved tupe.
radiation problem. High voltage should always be kept at the anufacture,s
rated value-no higher - for optimum performance. Every time a color set is
Parts Replacement
serviced, the brightness should be run up and down while monitoring the
Many electrical and mechanical parts in Philips television sets have special
HV with a meter to be certain that the HV is requlated correctlv and does
safety related charcteristics. These characteristics are often not evident from
not exceed the specified value. We suggest that you and your technicians
visual inspection nor can the protection afforded by them necessarily be
review test procedures so that HV requation are always checked as a
obtained by using replacement components rated for higher voltage, wattage,
standard servicing procedure, and the reason for this prudent routine is
etc. The use of a substitute part which does not have the same safety
cleary understood by everyone. It is important to use an accurate and
characteristics as the Philips recommended replacement part shown in this
reliable HV meter. It is recommended that the HV recorded on each
service manual may create shock, fire, or other hazards
customer's invoice, which will demonstrate a proper concern for the
customer's safety.
5. When troubleshooting and making test measurements in a receiver with
a problem of excessive high voltage, reduce the line voltage by means of
a Variac to bring the HV into acceptable limits while troubleshooting. Do
not operate the chassis longer than necessary to locate the cause of the
excessive HV.
WSRNING:Before removing the CRT anode cap, turn the unit OFF and short the HIGH VOLTAGE to the CRT DAG ground.
SERVICE NOTE:The CRT DAG is not at chassis ground. |
ACEC
PHILIPS
