Chapter 6. Failure Diagnosis; Outline Of Control; Check Mode Of Defrost Heater (Forced Defrosting); Re-Setting Of Microcomputer At Power Failure - Sharp SJ-C20 SL Series Service Manual

SJ-C19SS/C20XX

CHAPTER 6. FAILURE DIAGNOSIS

[1] OUTLINE OF CONTROL

1 . O N/ O F F C o n t r o l o f C o m p r e s s o r
• O N / OF F o f t h e c o m pr e s s o r wi l l be c on t r olled depend o n t he t em pe r a t u r e de t e c t e d b y t he R- t hermis t or . (Nor m a l c oo l ing con t rol )
• W h en t he rapid ice ma k i ng i s r eques t ed by user du r i ng t he opera t i o n , t h e c o mpr e ssor will be O N and c ool i ng o p e r a t ion wil l b e s t a r t ed
r egardles s o f t he de t ec t ed t e m pera t ure b y t he t her m i s t o r s . Howeve r , i f reque s t ed d u ring t he de f ro s t ing ope r a t ion , t he r e que s t wil l be e x e cu t e d
a ft e r t he c o mple t i on o f de f ros t i n g and O N o f t he c o mp r e ssor migh t b e delayed .
• D uring 5 minu t es a f t e r t he co m p res s or s t o p s , i t w i ll no t s t ar t regardle s s o f t he de t e c t ed t e m pera t ure by R - t he r mis t or.
2. Defrosting
M i c r oco m pu t e r c a l c ula t es t he appr o p ria t e t i m i ng o f de f ros t ing and de f ros t i ng is made au t o m a t i c al l y . T here f o r e no manu a l opera t i o n b y us e r i s
require d . T he c y cle o f de f ros t ing v a ries depend o n t he u s age c o nd i t ion o f t h e re f r i g e r a t o r . ( M aximu m t i me abou t 50 hours , m i n i m um t i m e 40 minutes. )
3 . T h e r m i s t o r
T her m i s t or s a r e ins t alled in 2 place s ; in t he r e f r igera t or , an d clo s e t o t he E v apora t o r . ( R - t he r mis t o r , De f - t he r m i s t o r )
R- t her m i s t o r de t ec t s t he t e mpera t ure i n t he re f r igera t or co m p ar t m en t r e spec t i vely and c on t r o l s O N / OF F o f com p resso r .
De f - t h ermis t or de t e c t s t he t e mpe r a t ure around t h e eva p ora t o r and show s t he p r ogress o f de f ros t ing .

[2] CHECK MODE OF DEFROST HEATER (Forced Defrosting)

T h e o p e r a t i on o f t h e de f r os t h e a t e r c a n be c he cke d b y s t a r t i n g i t .
I n c a s e t h e f ailu re o f d e f r o s t in g is s u sp ec t e d , t h i s i s a n e f f e c t i v e in sp e c t i o n me t h od .
1 . S t a r t i ng M e th o d
A t t he p o we r O F F c ond i t i on .
1 ) K e ep t h e do o r o f t h e r e f r ige ra t o r c o m p a r t m e n t ope n .
2 ) S e t t he T e m p . C o n t ro l K n ob in t he r e f r i ge r a t o r c o m p a r t m en t t o t h e center po s i t i on .
3 ) K e e p t h e d o or o pe n a n d s up p l y p o we r s o u rc e .
2 . N o rm a l O p e r a t i o n
1 ) A p pr o x i m a t e l y 3 sec o n d s a f t er p o w er s uppl y , t he r e la y o n t h e P W B will b e t u r ne d O N a n d t h e d e f r o s t he a t e r will b e e le c t r i f i e d f o r 5 s e co n ds .
2 ) A ft e r 5 s e c ond s , i f t he t e m p er a t u r e o f De f - t h e r m i s t o r r e aches h i g h e n ou gh (o v e r 1 0 ° C ) and j udg e d a s d e f ro s t i ng c o m pl e t i o n , t h e c o m p r e s s or will be
wait 5 seconds before r un s f o r 5 m i nu t e s a nd t h e n r e t u r n s t o t h e no r m al c o n t r o
O n t h e o t h e r ha n d , i f t h e t e m p er a t u r e o f De f - t h e rm i s t o r i s s t ill l o w (u nd er 1 0 ° C) , t he de f r o s t hea t e r w ill b e e l e c t r i f ie d u n t il t he t e m p e r a t u r e o f D e f -
t h e r m i s t or r e ac h e s t he s p e c i f i e d t e m per a t u r e o r h i g he r .
A ft e r c o m p l e t i on o f e l e c t r i f ic a t i on , t h e co m p ress o r r u n s f o r 5 m i nu t e s and t hen r e t u r n s t o t h e no r m a l c o n t r o l .
* I n t he ca s e t h a t a n y a b no rm ali t y in Do or Swi t c h , V o l u m e , R - t h er m i s t or o r D e f - t her m i s t o r , or t h e T e m p . C o n t ro l K no b i s n o t i n t h e po s i t i o n c o rr e -
sp ond i ng t o t he v al ue o f t he ra t i n g v ol t age s e t t l e d t o t h e P W B i t se l f , t h i s m o d e will n o t be en t er e d n o r t he d e f r o s t h e a t e r is e l e c t r i f ied .

[3] RE-SETTING OF MICROCOMPUTER AT POWER FAILURE

• At the power failure for over 0.25 second, the control of the microcomputer will might be reset.
• Microcomputer might continue to operate for approximately 10 seconds maximum at power failure depending on the load at the operation. Approx-
imately 30 seconds is necessary for the definite power OFF condition.
• When the power is re-supplied, the normal cooling will be resumed.(If cold enough in the cabinet, the microcomputer will begin defrosting in 40
minutes according to the condition.)
• The temperature and operation mode set by user will be maintained even if a power failure occurred.
(However defrosting, rapid ice making, and timer will not be maintained.)
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