Tandy 6000 HD, Service Manual

Page: 265 / 416

D a ta re c o v e ry e le c tro n ic s in c lu d e a lo w - le v e l
r e a d a m p lif ie r , f i l t e r , d if f e r e n t ia t o r , z e ro
cro s s o v e r d e te c to r, a n d d ig it iz in g c ir c u its . N o
' d a ta -c lo c k s e p a ra tio n is p ro v id e d .
I n a d d itio n , th e d r iv e is s u p p lie d w i t h th e f o l ­
lo w in g se n so r s y s te m s :
1. A T r a c k 0 se n so r d e te c ts w h e n th e
H e a d /C a rria g e A s s e m b ly is p o s itio n e d
o v e r T r a c k 0.
2. T h e T M 8 4 8 -2 E h a s tw o in d e x sensors,
e a c h c o n s is tin g o f a n in f r a r e d L .E .D .
l i g h t so u rce a n d a p h o to tr a n s is to r , p o s i­
tio n e d to g e n e ra te a s ig n a l w h e n a n
in d e x h o le o n th e d is k e tte is d e te c te d .
T h e d r iv e c a n d e te r m in e i f a s in g le -
s id e d o r d o u b le -s id e d d is k e t t e is
in s ta lle d . T h is o u t p u t s ig n a l is p re s e n t
a t th e in te r fa c e .
3. A W r it e P r o te c t se n so r d is a b le s th e
w r it e e le c tro n ic s w h e n a w r ite - e n a b le
ta b is re m o v e d fr o m th e d is k e tte .
A t h i r d te s t m o n ito r s th e in d e x sensors w h e n ­
e v e r th e d is k e t t e le v e r is closed. A d is k e tte
m u s t be in s e r te d in t o th e d r iv e f o r t h is te s t. I f
t h e d is k e tte le v e r is closed w it h o u t a d is k e tte
in p la c e , o r t h e s p in d le m o to r f a ils to o p e ra te ,
a n e r r o r m e ssa g e fla s h e s on th e f r o n t p a n e l
L .E .D . i n th e f o llo w in g sequen ce:
3 fla s h e s , th e n 4 : N o in d e x p u ls e w i t h
le v e r closed.
O p e n in g a n d c lo s in g th e d is k e tte le v e r is
r e q u ir e d to re p e a t a te s t t h a t h a s fa ile d . T h e
d is k e tte le v e r m u s t be l e f t open f o r one c o m ­
p le te e r r o r m e ssa g e c y c le .
1.5 PHYSICAL DESCRIPTION
A r e p r e s e n ta tiv e d r iv e is s h o w n i n F ig u r e 1-1.
T h e d r iv e c a n be m o u n te d i n a v e r t ic a l o r h o r i­
z o n ta l p la n e . H o w e v e r, th e lo g ic c ir c u it b o a rd
m u s t be o n th e u p p e rm o s t s id e w h e n th e d r iv e
is m o u n te d h o r iz o n t a lly .
T h e s p in d le is r o ta te d b y a d ir e c t d r iv e , b r u s h ­
less D . C. m o to r w i t h a n in t e g r a l ta c h o m e te r.
SELF-TESTS crystal 'contr°lle(i
s e rv o c ir c u i t a n d
ta c h o m e te r c o n tr o l th e speed o f th e s p in d le .
T h e d r iv e c o n d u c ts a p o w e r o n s e lf- te s t as p a r t
o f th e n o r m a l p o w e r o n sequence. T h e tw o
p o w e r o n te s ts do n o t r e q u ir e a d is k e tte to be
in s e rte d . T h e s e te s ts a re : th e h e a d c a r r ia g e
s te p p in g i n (a w a y fr o m T r a c k 0), a n d th e h e a d
c a r r ia g e s te p p in g o u t (to w a r d T r a c k 0). F a i l ­
u re o f e it h e r o f th e s e te s ts is in d ic a te d o n th e
f r o n t p a n e l L .E .D . b y th e f o llo w in g fla s h in g
s e q u e n c e :
3 fla s h e s , th e n 2 : F a ils to s te p i n fr o m
T r a c k 0 o r T r a c k 0
se n so r is a lw a y s e q u a l
to zero.
3 fla s h e s , th e n 3: F a ils to s te p o u t to
T r a c k 0 o r T r a c k 0
se n so r is a lw a y s e q u a l
to one.
O p e ra to r access f o r d is k e tte lo a d in g is p ro ­
v id e d v ia a h o r iz o n t a l s lo t lo c a te d a t th e f r o n t
o f th e d r iv e .
T h e r e a d / w r it e d o u b le -h e a d a s s e m b ly is p o s i­
tio n e d b y a s p l i t b a n d p o s itio n e r m o u n te d to a
m ic ro p ro c e s s o r-c o n tro lle d s te p p e r m o to r . T h e
r e a d / w r it e h e a d s a re g la s s -b o n d e d , f e r r i t e /
c e ra m ic s tr u c tu r e s w i t h a l i f e e x p e c ta n c y o f
1 5 ,0 0 0 o p e r a tin g h o u rs .
T h e c o n tr o l e le c tr o n ic s o f th e d r iv e a re
m o u n te d o n a p r in t e d c ir c u it b o a rd lo c a te d
a b o ve th e c h a s s is . P o w e r a n d in te r fa c e s ig n a ls
a r e r o u t e d t h r o u g h c o n n e c to rs p lu g g in g
d ir e c t ly i n t o th e lo g ic c ir c u it b o a rd . A second
c ir c u it b o a rd , m o u n te d u n d e r th e d r iv e , o p e r­
a te s th e b ru s h le s s D . C. s p in d le m o to r.
1-3