Safety Check Process
Safety Checks
After the original service p roble m has been corrected, a complete safet y check
should be made. Be sure to check o ver the e ntire set, not just the areas whe re
you have worked. Some previo us serv ice may have left an unsafe condition,
which could be unknowingly p assed o n to your customer. Be sure to check all
of the following:
Fire and Shock Hazard
1. Be sure all components are po sitio ned in such a way as to avoid the
possibility of adjacent co mpone nt shorts. This i s especially important on those
chassis which are transpor ted to an d form the service shop.
2. Never release a repaired un it unle ss all protective devices such as
insulators, barries, cov ers, st rain reliefs, and other hardware hav e been
installed in accordance wi th the or iginal design.
3. Soldering and wiring must b e inspe cted to locate possible cold solder jo ints,
solder splashes, sharp sol der poi nts, frayed leads, pinched leads, or d amage d
insulation(including t he acco rd). Be certain to remove loose solder b alls an d all
other loose foreign partic les.
4. Check across-the-line c ompon ents and other components for physic al
evidence of damage or deteri ortio n and replace if necessary. Follow original
layout, lead length and dres s.
5. No lead or component should t ouch a re ceiving tube or a resistor rated at
1watt or more. Lead tension ar ound pr otruding metal surfaces or edges mus t
be avoided.
6. Critical components hav ing spe cial safety characteristics are id entif ied with
ans bythe Ref.No in the parts li st and en closed within a broken line *( Where
several critical compone nts are g rouped in one area) along with the safet y
symbols on the schematic dia grams a nd/or exploded views.
7.When servicing any unit, a lways u se a separate isolation transforme r for the
chassis failure to use a separ ate iso lation transformer may expose you to
possible shock hazard, and m ay caus e damage to servicing instruments.
8. Many electronic product s use a pol arized ac line cord(one wide pin on the
plug). Defeating this safe ty feat ure may create a potential haza rd to the
service and the user. Extensio n cords w hich do not incorporate the polarizi ng
feature should never be used .
9. After reassembly of th e unit, a lways p erform an leakage test or resis tance
test from the line cord to all exp osed me tal parts of the cabinets. Also che ck all
metal control shafts(wit h knobs r emoved), antenna terminals, hand les, sc rews,
etc. To be sure t he unit may be safety operated without d anger o f electrical
shock.
* Broken line
Implosion
1. All picture tubes used in curre nt mode l receivers are equipped with an
intergral implosion syst em care s hould always be used, and safety glass es
worn, whenever handling an y pictu re tube. Avoid scra tchin g or other wise
damaging the picture tube du ring in stallation.
2. Use only replacement tube s speci fied by the manufacturer.
X-radiation
1. Be sure procedures and inst ructi ons to all your service personal cover t he
subject of X-radiation. Po tenti al sources of X-rays in TV receivers are the
picture tube and the high volt age cir cuits. The basi c precaution which must be
exercised is to keep the high vo ltage a t the factory recommended level.
2. To avoid pos sible exposure to X-radiation and el ectri cal sho ck, only the
manufacturer’s s pecified anode connectors must be us ed.
3. It is essential that t he serv ice tec hnician has an accurate HV mete r avail able
at all times. The calibration of this meter sho uld be ch ecked periodically against
a reference standard.
4. When the HV circuitry isope ratin g properly there is no possibility of an X radiation problem. High vo ltage s hould always be kept at the manufactur e,
rated value-no higher- for o ptimu m performance. Every time a color set is
serviced, the brightness s hould b e run up and while monitoring the HV with a
meter to be certain that the HV is r equat ion correctly and does not exce ed the
specified value. We suggest that you and your t echni cians review test
procedures so that HV requat ion are a lways checked as a standard servicin g
procedure, and the reason fo r this pr udent routine is cleanly understoo d by
everyone. It is important ot u se an acc urate and reliable HV meter. It is
recommended that the HV reco rded on e ach customer ’s invo ice, wh ich will
demonstrate a proper conce rn for th e customer’s s afety.
5. When troubleshooting an d makin g test measurements in a receiver with a
problem of excessive high vo ltage , reduce the line voltage by means of a vari ac
to bring the HV into acceptabl e limit s while troubleshooting. Do not oper ate the
chassis loner than necessa ry to loc ate the cause of the excessive HV.
6. New picture tubes are speci fical ly designed to withstand higher oper ating
voltages without creatin g undes irable X-radiation. It is strongly r ecomm ended
that any shop test fixt ure whi ch is to be u sed with the new higher voltage
chassis be equipped with one o f the new t ype tubes designed for this service.
Addition of a permanently co nnect ed HV meter to the shop test fixtur e is
advisable. The CRT types used in t hese ne w sets should never be replaced
with any other types, as this ma y resul t in excessive X-radiation.
7. It is essential to use t he spec ified p icture tube to avoid a possible X-radi ation
problem.
8. Most TV receivers contain come types of emer gency ” Hold Down” circuit to
prevent HV from rising to exce ssive l evels in the presence of a failure mode.
These various circuits sho uld be un derstood by all technicians servic ing the m,
especially since many hold d own cir cuits are inoperative as long as the
receiver performs normal ly.
Leakage Current Cold Check
1. Unplug the ac line cord and con nect a ju mper between the two prongs of the
plug.
2. Turn on the power switch.
3. Measure the resistance va lue bet ween the jumpered ac plug and all expose d
cabinet parts of the receive r, such as sc rew heads, antennas, and control
shafts. When the expo sed met allic p art has a return path to the chassi s, the
reading should be between 1 me gohm an d 5.2 megohms. When the exposed
metal does not have a return pat h to the ch assis, the reading must be infi nity.
Remove the jumper from the ac li ne cord .
Leakage Current Hot Check
1. Do not use an isolation trans forme r for this test. Plug the complet ely
reassembled receiver dir ectly i nto the ac outlet.
2. Connect a 1.5k, 10w resisto r paral leled by a 0.15uf capacitor between ea ch
exposed metallic cabinet p art and a g ood earth ground such as a water pipe, as
shown above.
3. Use an ac voltmeter with at lea st 5000 o hms volt sensitivity to measu re the
potential across the resis tor.
4. The po tential at any point should not exceed 0 .75 vol ts. A leakage current
tester may be used to make this te st; lea kage current must not exceed a
possibility of shock hazar d. The receiver s hould b e repaired and rechecked
before returning it to the cus tomer.
5. Repeat the above procedur e with th e ac plug reversed.(note: an ac adapte r
is necessary when a polarize d plug is u sed. Do not defeat the polarizing
feature of the plug.)
Picture Tube Replacement
The primary source of X-radi ation i n this television receiver is the pict ure tub e.
The picture tube utilized in t his cha ssis is specially constructed to lim it Xradiation emissions. For c ontin ued X-radiation protection, the re place ment
tube must be the same typ es as the o rigin al, including suffix letter, or a Philips
approved tube.
Parts Replacement
Many electrical and mechan ical pa rts in Philips television sets have sp ecial
safety related character istic s. These c harac teristics are often not evide nt from
visual inspection nor can th e prote ction afforde d by them necessarily be
obtained by using replacem ent com ponents r=ated for higher voltage, w attag e,
etc. Th e use of a substitute part which does not ha ve the sa me safety
characteristics as the Phi lips re commended replacement part shoul d in this
service manual may create sh ock, fi re, or other hazards.