V-28BT8EES / AV-28BT8EEB/ AV-28BS88EN
4
SAFETY PRECAUTIONS
1. The d esi gn of th is pr od uct con ta in s sp ecial har d wa re , ma ny
circuits and components specially for safety purposes. For
con tinu ed pr ot ecti on , n o chan g es sh ou ld b e ma de to the o rig inal
d esi gn un less a uth or ized i n w ritin g by th e ma nu fact ur er.
Rep lacem en t p ar ts m ust b e i d ent ic al to thos e u sed i n th e or igi n al
ci rcu it s. Se r vic e sh ou ld be pe rf or me d b y q ua li fie d per so nn el
on ly.
2. Al te r ati on s of t he desi g n or ci rcuitr y of t he pr od ucts sh oul d not be
made. Any design alterations or additions will void the
m anu fact ur er's w arr a nt y and wi ll f ur th er r eli eve t he ma nu factu r er
of r esp onsi b il ity for perso na l injur y or p rop er ty d am ag e resul t in g
th er efr om .
3. M an y e l ectr ical an d mech ani ca l p ar ts i n th e pr od ucts ha ve
special saf ety-related characteristics. T hese characteristics are
oft en no t e vi den t f r om vi sua l i nsp ection n or ca n t he pro tect io n
aff or de d by th em nece ssar ily b e ob tain ed b y u sin g rep l acem en t
com po ne nts ra ted f or hig he r vo l tag e, watt ag e, etc. Rep lacem en t
p arts wh ic h ha ve th ese sp eci al s afet y ch ar act er ist ics ar e
identified in the parts list of Servic e manual. El ec tric al
components having su ch features ar e identified by shading
on the sche matic s and by (!
!!
!) on the parts list in Service
manual. The us e of a sub sti tu te r ep la cem en t which do es n ot
h ave th e sam e saf ety ch ar act er ist ics as t he r eco mmen de d
r eplac em ent par t sh own i n th e p ar ts l ist of S er vi ce m an ual m ay
cause shock, fire, or other hazards .
4. Do n't shor t between the LIVE side ground and ISOL ATE D
(NEUTRAL) side ground or EARTH side ground when
repairing.
Some model's power circuit is partly different in the GND. The
diff er enc e of the GND i s sh own b y th e LI VE side G ND, th e
ISO LATE D(NEUTRAL) sid e GND a nd EA RTH side GND. Don't
sh ort b etw ee n the L IVE side GN D a nd IS OLATE D( NEUTRAL)
side GND or EA RTH side GND and ne ver meas ure with a
m easu r in g app ar atu s ( osc ill osc ope et c.) th e LIV E sid e GND an d
ISOLATED(NEUTRAL) side GND or EARTH side GND at the
same time.
If above note will not be kept, a fuse or any parts will be broken.
5. If any repair has been made to the chassis, it is recommended
th at t he B1 set ti ng shou l d b e ch ecke d or adj u ste d ( Se e
ADJU STMENT OF B 1 POW E R SUPPL Y).
6. The hi gh vol ta ge app lie d t o th e pictu r e tu be mu st con for m wit h
th at sp eci fi ed in S er vice m an ual. E xcessi ve h i gh vo lt ag e ca n
cau se an incr e ase in X- Ray em issi on , ar ci ng an d possi b le
component damage, therefore operation under excessive high
voltage conditions should be kept to a minimum, or should be
preve nt ed. If s evere arc ing occurs, remove t he AC power
immed iate l y an d de ter mine th e ca use b y visua l insp ect io n
( in cor rect in stal lat i on, cr acke d or m elte d hi gh vo lt age har n ess,
p oor so ld eri ng, et c.) . To m aint ai n the p r ope r min imu m l e vel of
sof t X- Ray emi ssion, c omp on en ts in th e hi gh voltag e cir cuitr y
incl ud ing t he pi ct ur e tu be must b e t he e xact r ep lacem e nts or
alte rn at ives ap pr ove d b y th e ma nuf act ur er of th e c om plet e
pr od uct.
7. Do n ot c hec k high volt ag e b y drawing an arc. Use a high volt ag e
m eter or a hi g h v oltag e pr ob e wit h a V T VM. D ischa rg e th e
picture tube before attempting meter connection, by connecting
a cl ip le ad to th e gr ou nd f ra me a nd c onn ecti n g th e oth er end of
the lead through a 10kΩ2W resi sto r to the an od e b utt on .
8. W hen se r vi ce is r equ ir e d, ob ser ve th e or igi na l lea d dr ess. E xtr a
pr ec aut i on sh ou ld b e g ive n t o assur e cor r ect l ea d dr ess i n th e
hig h voltag e cir cuit a r ea. W here a s hor t cir cui t h as occu rr e d,
th ose co mp on ent s tha t i ndica te evi de nce of ove r hea ting sho uld
b e r e place d. A l wa ys u se th e ma nuf act ur er 's r ep lacem en t
components.
9. Isolation Check
(Safety for Electrical Shock Hazard)
Af ter r e-ass emb lin g th e p r odu ct, al ways per f orm an i sol at io n
ch eck on the expo sed me tal p ar ts of t he cabin et ( a nte nn a
ter m ina ls, vid eo /au dio i npu t and ou tpu t t er mi n als, Con tr ol kn obs,
metal cabinet, screwheads, earphone jack , control shafts, etc.)
to be su re th e p r odu ct is s af e t o o pe r ate with ou t d an ger of
elect rical shoc k.
(1) Dielectric Strength Test
The iso l ati on be tw een the A C pr im a ry ci rcu i t an d all me tal p ar ts
exp ose d t o th e us er , p ar ti cular ly an y e xp os ed met al p art h avi ng a
r etu rn p ath to t he chass is sho uld withs tan d a volt age of 3 000 V
AC (r.m.s.) for a period of one second.
( . . . . W it hstan d a vo lt ag e of 1 10 0V A C ( r .m. s.) t o an ap pl ianc e
r ate d up to 12 0V , an d 3 00 0V AC ( r.m. s.) to an ap pli an ce r at ed
200V or more, for a periodof one second.)
This method of test requ ires a t est equipment not generally found
in t he servic e trad e.
(2) Leakage Current Check
Pl ug th e A C lin e c ord d ir ect l y in to th e A C ou tl et ( d o n ot use a lin e
isol ati o n tr ansf or m er du r in g thi s ch eck.) . Usi n g a " Lea kag e
Cur rent Teste r", me asur e th e l ea kag e cu rre nt f rom each exp osed
m etal p ar t of the ca bi ne t, p art icu lar ly any e xpos ed me tal p ar t
h aving a re turn pa th to t he ch assis , t o a kn own go od ea rt h
gr ou nd (wa ter pip e, e tc.) . An y l eaka ge cur ren t m ust n ot e xceed
0.5mA AC (r.m.s.).
Howeve r, i n tr op ic al area , th is mu st no t exce ed 0.2 mA AC
(r.m.s.).
"
""
"Alte rnat e Ch e ck Met hod
Pl ug th e A C lin e c ord d ir ect l y in to th e A C ou tl et ( d o n ot use a lin e
isol ati o n tr an sfor mer dur ing t hi s che ck.) . Use an AC vo lt me ter
h avi ng 1 00 0 oh ms pe r volt or mor e sens it i vi ty in th e fo llow ing
m ann er. Con nec t a 1 50 0Ω10W res ist or par a ll e le d b y a 0 .1 5µF
AC -type c apa cit or bet we en an expo sed met al pa rt a nd a kno wn
g ood e ar th gr o un d ( wa ter pipe , etc.) . M eas ur e th e A C vo lt ag e
acr oss th e r es ist or wi th th e AC vo ltm eter . Move th e r esi stor
con nec ti on to e ach exp ose d me tal par t, p art icul arly a ny exp osed
m etal p ar t havi n g a retu rn pat h to t he ch assis, an d m easu r e th e
AC vol tag e ac ro ss the r es ist or . No w , re ver se th e plu g i n th e AC
ou tl et and r e pe at eac h m ea sur emen t. An y vol t ag e me asu re d
mu st not exc eed 0.75V AC (r.m. s.). This c orre sponds to 0.5mA
AC (r.m.s.).
However, in tropical area, this must not exce ed 0.3V AC ( r.m.s.).
This corresponds to 0.2mA AC (r.m.s.).
0.15μF A C-T YP E
1500 Ω10W
GOODEARTH GROUND
PLACE THIS PROBE
ON E A CH EX PO SE D
ME T AL PA R T
ACVOLTMETER
(HAVING 1000 Ω/V,
OR MOR E SENSIT IVITY)
