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T a b l e 5 . 2
Problem
S o l u t i o n
1) I n s t r u m e n t blows f u s e s .
Check f u s e s i z e and l i m i t s .
Make s u r e
S 1 i s s e t f o r p r o p e r l i n e v o l t a g e .
Check
f o r any s h o r t s between S 2 and i n s t r u m e n t
c a s e .
2) I n s t r u m e n t g e t s ex-
Check C7, and CR7-8 f o r p r o p e r o p e r a t i o n .
c e s s i v e l y h o t .
F a i l u r e of t h e s e components w i l l r e s u l t i n
T X 1 warming up.
A l s o check f o r any s h o r t s
between any of t h e l e a d s of TX1.
3 ) A/D c o n v e r t e r d r i f t s .
Check p e r i o d of waveform b , T a b l e 5.1.
I f
p e r i o d i s i n c o n s i s t e n t (should be ~.8 s e c ) ,
t h i s w i l l c a u s e A/D c o n v e r t e r t o d r i f t .
T h e r e f o r e , r e p l a c e U20, and a l s o check C30.
4)
D i s p l a y seems t o f l i c k e r .
Check f o r any s h o r t s between p i n s 2 and 3
going t o t h e d i s p l a y b o a r d .
Check t o make s u r e +5 V and ground go t o t h e
on U 3 and U 5 are h i g h ( f o r example, i f 100.0
were d i a l e d i n , t h e o n l y l i n e on would be
t h e most s i g n i f i c a n t d i g i t , d i g i t
1 ) .
I f
t h e p r o p e r l i n e s are on and i t does n o t
r e s p o n d , check and see i f t h e c o n t r o l s i g n a l
i s p r e s e n t (U6 of p i n 9 ) .
T h i s should be
h i g h when c o n t r o l i s on.
I f s i g n a l i s p r e s e n t ,
t h e n problem i s i n power board
-
probably U 4 0 .
I f s i g n a l i s s t i l l n o t t h e r e , t r a c e c o n t r o l
s i g n a l back t h r o u g h U 1 9 t o t h e CPU
(U17
I/O
p o r t 2 ) .
The d i s c o n t i n u i t y of t h e
s i g n a l would b e t h e f a i l u r e of e i t h e r U 6 ,
U19 o r U17.
5)
C o n t r o l l e r does n o t respond t o
s e t p o i n t s w i t c h e s .
s w i t c h e s .
I f s o , check t h a t t h e p r o p e r l i n e s
6) Power s t a y s on all t h e
t i m e ,
Check
U 4 4 .
I f t h i s power D a r l i n g t o n i s
no m a t t e r what s e t p o i n t i s .
7) C o n t r o l does n o t respond and
b a d , t h e power w i l l s t a y h i g h a l l t h e t i m e .
Problem c o u l d b e i n c o n t r o l PROM U 1 4 .
c o n d i t i o n s 5 and 6 check o u t .
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