V28BH7EES / AV28BH7EEB
4
SAFETY PRECAUTIONS
1. The d esign 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 ti nu ed pr ot ection , n o chan g es sh ou ld b e ma de to the o ri g inal
d esign un l ess a uth or ized i n writin g by th e ma nu fact ur er .
Rep l acemen t p ar ts m ust b e i d ent ic al to thos e u sed i n th e or igin al
circu it s. Se r vic e sh ou ld be pe rf or me d b y q ua lifie d per so nn el
on ly.
2. Al te r ation s of t he desi g n or ci rcui tr 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 warra 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 inj ury or p r op erty d am ag e r esult in g
th er efr om .
3. M an y e l ectr ical an d m ech ani ca l p ar ts i n th e pr od ucts ha ve
special safety-relat ed characteristics. T hese charact eristics are
oft en no t e vi den t f r om visua l insp ecti on n or ca n t he pr o tect io n
aff or de d by th em nece ssar ily b e ob tai n ed b y u sin g r ep lacem en t
com po ne nts ra ted f or hi g he r vo l tag e, watt ag e, etc. Rep lacem en t
p arts wh ic h ha ve th ese sp ecial 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 matics and by (!
!!
!) on the parts list in Service
manual. T he us e of a sub sti tu te r ep la cem en t w hich do es n ot
h ave th e sam e saf ety ch ar act er ist ics as t he r eco mm en de d
r eplac em ent par t sh own i n th e p ar ts li st of S er vi ce m an ual may
cause shock, fire, or other hazards .
4. Do n't shor t between the LIVE side ground and ISOL ATED
(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 GN D i s sh own b y th e LI VE side G ND , th e
ISO LATE D(N EUTRAL) sid e GND a nd EA RTH side GND. Don' t
sh ort b etwee n the L IVE si de GND a nd IS OLATE D( NEU TRAL)
side GND or EA RTH side GND and ne ver meas ure with a
m easu r in g app aratu s ( osc il losc ope et c.) th e LIV E si d 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 ting shou ld b e ch ecke d or adju ste d ( Se e
ADJUSTMENT OF B 1 POW E R SUPPL Y).
6. The hi gh volta ge app lie d t o th e pictu re tu be mu st con for m wi t h
th at sp eci fied i n S er vice m an ual. E xcessive h igh vo lt ag e ca n
cau se an i ncre ase i n X- Ray em ission , ar cing an d possib 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 in g occurs, remove t he AC power
imm ed iate l y an d de ter m ine th e ca use b y vi sua l i nsp ect io n
( in cor rect in stall at ion, cr acke d or m elte d hi gh vo lt age har n ess,
p oor so ld er ing, et c.). T o m aint ai n the p r ope r min im u m l e vel of
sof t X-R ay em issi on, c omp on en ts in th e hi gh voltag e ci rcui tr 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 ar c. Use a high volt ag e
m eter or a hi g h v oltag e pr ob e wi t h a V TVM. 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 ectin g th e oth er end of
the lead through a 10kΩ2W resisto r to the an od e b utt on .
8. W hen se r vice is requ ire d, ob ser ve th e or igina l l ea d dr ess. E xtr a
pr ec aut i on sh ou ld b e g ive n t o assur e cor rect l ea d dr ess in th e
hig h vol tag e cir cuit a r ea. W her e a s hor t ci rcuit h as occu rr e d,
th ose co mp on ent s tha t indi ca te evide nce of ove r hea ti ng sho uld
b e r e place d. A lwa ys u se th e ma nuf act ur er's rep l acemen t
components.
9. Isolation Check
(Safety for Electrical Shock Hazard)
Af ter r e-ass emb lin g th e p r odu ct, alw ays per f orm an isol 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 min al s, C on tr ol kn obs,
metal cabinet, screwheads, earphone jack , control shafts, etc.)
to be su re th e p r odu ct i s 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 lation be tween the A C prima ry ci rcu it 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 aving 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 pl ian ce r at ed
200V or more, for a period of one second.)
This method of test requires 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 irect l y in to th e A C ou tl et ( d o n ot use a li n e
isol atio n transf or mer du r in g this ch eck.) . U sin g a " Lea kag e
Cur r ent T este r" , me asur e th e lea kag e cu rre nt f rom each exp osed
m etal p ar t of the ca bine t, p art icu l arl y any e xpos ed me tal p ar t
h aving a re tur n 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 leaka ge cur r en t m ust n ot e xceed
0.5mA AC (r.m.s.).
How eve r, i n tr op ic al ar ea , th is mu st no t exce ed 0.2 mA AC
(r.m.s.).
"
""
"Alte rnat e Che ck M ethod
Pl ug th e A C lin e c ord d irect l y in to th e A C ou tl et ( d o n ot use a li n e
isol atio n tran sform er dur ing t hi s che ck.) . Use an AC vo lt me ter
h aving 1 00 0 oh ms pe r vol t or m ore sens it i vity in th e fo llow ing
m ann er. C on 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 pi pe , etc.) . M eas ur e th e A C vo lt ag e
acr oss th e r es ist or w ith th e AC vo ltm eter . M ove th e r esi stor
con nec tion to e ach exp ose d me tal par t, p art icul arl y a ny exp osed
m etal p ar t havi n g a retu rn pat h to t he ch assis, an d measu r e th e
AC voltag e ac ro ss the r es ist or . No w , re ver se th e pl u g i n th e AC
ou tl et and r e pe at eac h m ea sur emen t. An y volt ag e me asu re d
mu st not exc eed 0 .75V AC (r.m. s.). This c orresponds 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 YPE
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)
