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SECTION V
T r o u b l e s h o o t i n g
5.1
I n t r o d u c t i o n
T h i s s e c t i o n c o n t a i n s t h e i n s t r u c t i o n s f o r m a i n t a i n i n g and t r o u b l e -
s h o o t i n g t h e
DRC-7/70
s e r i e s of i n s t r u m e n t s .
5.2
T e s t Equipment and A c c e s s o r i e s
A h i g h i n p u t impedance d i g i t a l v o l t m e t e r a n d o s c i l l o s c o p e ,
a f i f t y ohm,
t e n w a t t r e s i s t o r t o s i m u l a t e a h e a t e r element ( i n t h e c a s e of c o n t r o l l e r s )
and a p r e c i s i o n r e s i s t o r connected t o s i m u l a t e t h e d i o d e w i r e d a c c o r d i n g t o
F i g u r e 2 . 1 ( c ) are n o r m a l l y s u f f i c i e n t t o test t h e
DRC-7/70
i n s t r u m e n t s .
5.3
General Remarks
On i n s t a l l a t i o n , one of t h e major problems i s a n i m p r o p e r l y connected
t e m p e r a t u r e s e n s i n g d i o d e .
It i s a d v i s e d t h a t o t h e r p o r t i o n s of t h e c r y o g e n i c
system b e t e s t e d b e f o r e t h e i n s t r u m e n t i s t r o u b l e s h o o t e d .
Some checks t h a t
could b e made are:
1)
Open o r s h o r t e d s e n s o r o r h e a t e r l e a d s ( e s p e c i a l l y i n a n
2) Leakage p a t h s between h e a t e r and s e n s o r l e a d s t h a t i n d u c e
area of f r e q u e n t d i s a s s e m b l y ) .
e l e c t r i c a l feedback i n a d d i t i o n
t o
t h e r m a l feedback.
I f t h e m a l f u n c t i o n p o i n t s toward t h e i n s t r u m e n t , more d e t a i l e d t e s t s
s h o u l d b e made.
5.4
I n s t r u m e n t Tests
The f i r s t check t o b e made would b e t o check t h e i n p u t l i n e f u s e .
A
3 / 4 Ampere, 250 V , f a s t - b l o f u s e
i s recommended.
I f t h e i n p u t l i n e v o l t a g e
and s e n s o r i n p u t v o l t a g e have been checked, t h e f o l l o w i n g sequence should b e
followed :
1) Check a l l t h e power s u p p l i e s f o r p r o p e r o p e r a t i o n .
The 5V s u p p l y
f u r t h e d i s p l a y s h o u l d b e between 3 . 8 and 5.0
V.
T h i s i s a n un-
f i l t e r e d b u t r e g u l a t e d s u p p l y .
Power s u p p l y l i n e s are i n d i c a t e d
on F i g u r e 6 . 4 .
w i l l r e s u l t
i n
your DRC i n s t r u m e n t n o t o p e r a t i n g p r o p e r l y .
5 . 1
f o r waveforms
The f a i l u r e of any of t h e s e s i x power s u p p l i e s
2)
Check f o r t h e waveforms
a t
t h e f o l l o w i n g p i n s and r e f e r t o F i g u r e
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