V-20NMG3B
3
SAFETY PRECAUTIONS
1. The d esign of th is prod uct con ta ins sp ecial hard wa re, ma ny
circuit s and components specially for safety purposes. For
con tinu ed prot ection , n o chan g es sh ou ld b e ma de to the o rig inal
d esign un less a uth orized in writin g by the manu fact urer.
Replacemen t parts must be id ent ic al to thos e u sed in th e original
circu it s. S ervice sho uld b e p erform ed by qualif ied pers on nel
on ly.
2. Alte ration s of t he desig n or circuitry of t he prod ucts sh ould not be
made. Any design alterations or additions will void the
manu fact urer's warra nt y and will f urther r elieve t he ma nu factu r er
of r esponsib ility for perso na l injury or prop erty d am ag e result ing
th er efrom.
3. M an y e lectr ical an d mech anica l parts in th e pr od ucts ha ve
special safety-related characteristics. T hese characteristics are
oft en no t e viden t f rom visua l insp ection n or can t he pro tect io n
aff orde d by th em nece ssarily b e ob tain ed b y u sin g rep lacemen t
compo ne nts rated f or hig he r voltag e, watt ag e, etc. Rep lacemen t
p arts whic h ha ve these sp ecial s afet y ch aract erist ics ar e
identified in the parts list of Servic e manual. El ec trical
components having su ch features are identified by shading
on t he sche matics and by (!
!!
! ) on the parts list in Service
manual. The us e of a sub stitute rep lacemen t which do es n ot
h ave th e same saf ety ch aract erist ics as t he reco mmen de d
replac ement par t sh own in th e p ar ts list of S ervice man ual may
cause shock, fire, or other hazards .
4. Do n't short between the LIVE side ground and ISOLATED
(NEUTRAL) side ground or EARTH side ground when
repairing.
Some model's power circuit is partly different in the GND. The
diff erenc e of th e G ND is sho wn b y th e LIV E : (") side GND, the
ISO LATE D(NEUTRAL) : (#) side G ND and EARTH : ($) side
GND. Do n't sh or t b et ween th e LIV E side GND an d
ISO LATE D(NEUTRAL) side GND or EARTH side GND and
n ever mea sur e wit h a m ea sur ing a ppa r atus (oscilloscop e etc.)
th e LI VE sid e GND an d IS OLA TED(NE UTRAL ) side G ND or
EARTH side GND at the s ame 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 checke d or adju sted ( See
ADJUSTMENT OF B 1 POW E R SUPPL Y).
6. The high voltage app lie d t o the pictu r e tu be mu st con form wit h
th at sp ecified in S er vice man ual. E xcessive h igh vo lt ag e ca n
cau se an incre ase in 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 ever e arc in g occurs, remove t he AC power
immed iate ly and de termine th e ca use b y visua l insp ect io n
(in correct in stallat ion, cr acked or melte d high vo lt age har n ess,
p oor soldering, et c.). To m aint ain the p r ope r min imu m le vel of
sof t X-Ray emission, c omp on en ts in th e high voltag e cir cuitry
includ ing t he pict ure tube must b e t he e xact rep laceme nts or
alte rnat ives ap prove d b y the manuf act urer of th e c omplet e
prod uct.
7. Do n ot c hec k high volt ag e b y drawing an arc. Use a high volt ag e
meter or a hig h v oltag e prob e wit h a V TVM. Discha rge the
picture tube before attempting meter connection, by connecting
a clip lead to th e grou nd f rame and c onn ectin g th e oth er end of
the lead through a 10kΩ 2W resisto r to the an od e b utt on .
8. W hen ser vice is requ ired, ob ser ve th e or igina l lea d dress. E xtra
prec aut ion sh ou ld b e g ive n t o assure correct lea d dress in the
high voltage circuit area. W her e a s hort circuit has occu rre d,
th ose compon ent s tha t indica te evide nce of ove r hea ting sho uld
b e re place d. A lwa ys use th e ma nuf act urer's rep lacemen t
components.
9. Isolation Check
(Safety for Electrical Shock Hazard)
Af ter re-ass emb lin g th e p r odu ct, always per f orm an isolat io n
ch eck on the expo sed me tal par ts of t he cabin et (a nte nn a
ter m ina ls, video /au dio input and ou tput t ermin als, Con trol kn obs,
metal cabin et, scr ewhe ad s, ea r ph one jack, con trol shaf ts, etc.)
to be su re th e p rodu ct is s af e t o o pe r ate with ou t dan ger of
elect rical shoc k.
(1) Dielectric Strength Test
The isolation be tween the A C prima ry circu it an d all me tal p ar ts
exp ose d t o th e us er, p articular ly an y e xp os ed met al p art h aving a
retu 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 plianc e
rate d up to 12 0V , an d 3 00 0V AC ( r .m. s.) to an ap pliance r at ed
200V or more, for a period of one second.)
This method of test requires a test equipment n ot generally found
in t he servic e trad e.
(2) Leakage Current Check
Plug th e A C line c ord d irect ly into th e A C ou tlet (d o n ot use a lin e
isolatio n transf or mer during this ch eck.) . Usin g a " Lea kag e
Current Teste r", me asur e th e lea kag e cu rre nt f rom each exp osed
metal p art of the ca bine t, p art icu larly 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
grou nd (wa ter pipe, e tc.). Any leaka ge curren t must n ot exceed
0.5mA AC (r.m.s.).
Howeve r, in tr op ic al ar ea , th is mu st no t exce ed 0.2 mA AC
(r.m.s.).
"
""
" Alte rnate Che ck M et hod
Plug th e A C line c ord d irect ly into th e A C ou tlet (d o n ot use a lin e
isolatio n tran sfor mer during t his che ck.). Use an AC vo lt me ter
h aving 1 00 0 oh ms pe r volt or m or e sens it ivity in th e fo llowing
mann er . Con nec t a 1 50 0Ω 10W res ist or para lle led b y a 0 .15µF
AC-type c apa cit or bet ween an exposed met al pa rt a nd a kno wn
g ood e ar th gro un d (wa ter pipe , etc.). Meas ure th e A C vo lt ag e
across th e res ist or with th e AC vo ltmeter. Move the r esistor
con nec tion to e ach exp osed metal par t, part icularly a ny exp osed
metal p art havin g a r etu rn pat h to t he ch assis, and m easu r e th e
AC voltag e ac ro ss the res ist or. No w, re ver se the plu g in th e AC
ou tlet and re pe at eac h mea sur emen t. An y volt ag e me asure d
must not exc eed 0.75V AC (r.m.s.). This c orresponds to 0.5mA
AC (r.m.s.).
Howeve r, in tropica l area, this must n ot exce ed 0.3V AC ( r.m.s.).
This corresponds to 0.2mA AC (r.m.s.).
0.15μF AC-T YPE
1500 Ω 10W
GOOD EARTH GROUND
PLACE THIS PROBE
ON E A C H EX PO SE D
ME T AL PA R T
AC VOLTMETER
(HAVING 1000 Ω /V,
OR MOR E SENSITIVITY)
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