Tandy 1000 SL Technical Reference Manual page 284

( p o o l y ) , s t e e l b e l t ( b a n d ) , and g u i d e s h a f t s . The head c a r r i a g e i s
c o n n e c t e d t o t h e c a p s t a n o f t h e s t e p p i n g motor through t h e s t e e l b e l t
and i s s l i d e d a l o n g t h e g u i d e s h a f t s .
The s t e p p i n g motor r o t a t e s
2
s t e p s ( 3 . 6 " ) i n 4 8 t p i model and 1 s t e p
(1.8') i n 9 6 t p i models f o r one t r a c k s p a c e .
of
head seek o p e r a t i o n and p r e c i s i o n
of
head p o s i t i o n i n g , h y b r i d t y p e
4-phase s t e p p i n g motor i s d r i v e n i n a unique manner which brought a
s u c c e s s i n r e d u c i n g t h e h e a t r a d i a t i o n and t o o b t a i n a h i g h l y p r e c i s e
p o s i t i o n i n g .
The p a r a l l e l i s m and t h e d i s t a n c e between t h e s h a f t s and t h e c e n t e r l i n e
of a d i s k , and s h a f t s and c a p s t a n t h e m s e l v e s a r e p r e c i s e l y machined.
A l s o
t h e t h e r m a l expansion o f t h e frame, s t e e l b e l t , c a r r i a g e , e t c . a r e
t a k e n i n t o c o n s i d e r a t i o n i n t h e p r o c e s s o f d e s i g n so t h a t t h e y a r e
m u t u a l l y o f f s e t w i t h t h e expansion o f t h e d i s k .
To improve t h e c o n t i n u i t y
(7) D e t e c t i o n mechanisms
( a ) F i l e p r o t e c t d e t e c t i o n mechanism
T h i s mechanism i s c o n s t r u c t e d w i t h an
LED and a p h o t o - t r a n s i s t o r t o
d e t e c t t h e e x i s t e n c e o f t h e w r i t e e n a b l e n o t c h o f t h e d i s k j a c k e t .
When a d i s k w i t h t h e notch covered i s i n s t a l l e d and t h e l i g h t p a s s
f o r d e t e c t i o n i s d i s t u r b e d , no w r i t e
or erase
c u r r e n t w i l l be s u p p l i e d
t o t h e r e a d / w r i t e and e r a s e heads and t h e r e c o r d e d i n f o r m a t i o n on t h e
d i s k i s p r o t e c t e d from an e r r o n e o u s i n p u t of a w r i t e command.
The LED i s mounted on t h e PCBA DD motor s e r v o and t h e p h o t o - t r a n s i s t o r
on t h e
PCBA
f r o n t
O P T .
(b) Track 00 d e t e c t i o n mechanism
T h i s mechanism i s c o n s t r u c t e d w i t h a p h o t o - i n t e r r u p t e r f o r d e t e c t i n g
t h e outermost t r a c k p o s i t i o n ( t r a c k 00) o f t h e head c a r r i a g e .
The p h o t o - i n t e r r u p t e r i s mounted on t h e main
PCBA (PCBA MFD
c o n t r o l ) .
I n s i d e t r a c k s from t h e t r a c k
00
on t h e d i s k
are
used. Even i f an
-
205
-