Diagnosis Method Of Failure - Sharp SJ-C20 SL Series Service Manual

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SJ-C19SS/C20XX

[4] DIAGNOSIS METHOD OF FAILURE

C h e c k b y t h e f o ll o wi n g pro c e d ur e ;

1 . D i s c on n e c t pow er s upp l y a nd c h e c k t h e f o l l o wing p o i n t .

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I s t he r e an y f a ilu r e p or t i o n in i n s e r t i ng co n n e c t o r s ?

2 . De t a c h t h e P W B a nd c h e c k t h e app e a r a nc e .

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I s t her e a n y b u rn i ng o r ab n o r ma l da m ag e ?

3 . Check t h e co n d i t io n s o f t he f u s e a nd t h e v a r i s t o r . ( F u se an d v a r i s t o r a r e l o c a t e d a t t he pos i t i on i n t he f i gure . )

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M e l t i n g i n t h e f use c an n o t b e c h e c ke d v i su all y ( a s t h e sa f e r o n e t h an t r a ns p a r e n t g l ass t u be i s u s ed) . B e s u re t o de t a c h t h e c o nn ec t o r "CN1 "

be f ore mea s u r i n g t h e r e s i s t a nce b e t w een t h e b o t h e n d s o f t h e f us e by t h e t e s t e r .

•

N e x t , m e a s ur e t h e r e s i s t a n c e v a l u e b e t we e n t h e b o t h l ea ds o f t h e v ar is t o r .

CN2

CN3

V a r i s t o r →

F u s e ↓

F l o w o f e x c e ss i v e c u r r e n t i s co n s i dera bl e f o r so m e r e a -

s on s .

M e l t i n g

C h ec k f o r a n y p o r t i on t o c a u s e s hor t c i r c u i t s e s pe c i all y

o n t h e p r i m a r y c i r c u i t .

F u s e a n d va r i s t o r a r e n o r m a l .

Po s s ib i li t y t o b e ca u s e d b y e x c e s s i v e c u rr e n t o r vol t a g e

C o nd uc t i o n

ne a r t he powe r s u p pl y i s lo w . P r o c eed t o t h e n e x t c he c k

i t e m .

4 . Check wh e t he r t h e t e m p er a t ur e ( r esis t a n c e v a l u e ) s h o w n by R - t herm i s t or i s c o rr e c t or n o t . ( Re f er t o t h e t a b l e b el o w . )

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D e t a c h t h e c on ne c t o r " CN3 " o n t h e P W B a n d me a s ur e t h e r e s is t an c e va lu e be t w e e n 2 a n d 4 p i n s .

5 . Check wh e t her t h e t e m pe ra t u r e ( r e s is t a n c e v a lue ) s h o w n by D e f - t h e r m i s t or i s co r r ec t o r no t . ( Re f e r t o t h e t ab le b e l o w . )

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D e t a ch t he c o nn e c t o r " CN 2 " o n t he P W B a n d m e a s ur e t he r e s is t a nc e v a lu e be t w ee n 1 an d 2 p i ns .

No r m a l ( s e v e r al hu n d re d s Ω ~ s e v er al K Ω

)

T here is a pos sibili t y o f e x c e s s iv e v o l t a ge a p p l ie d f r om o u t -

sid e w i t h t he f a c t o r su c h a s t hu n d e r e t c . W h e n r e p e a t e d

wi t h a f ac t or o t h er t h a n t h u n de r , t her e m i gh t b e t h e a p p a r a -

t u s ne a r by g e n era t in g n o i s e s .

—

6 – 2

CN1

F1(Fuse 8A)