Read Data Circuits - Tandy 6000 Service Manual

READ DATA CIRCUITS

T h e re a d e le c tro n ic s c o n s is t o f:
1. R e ad O n ly a n d S id e S e le c t c ir c u it
2. R e a d A m p lif ie r
F i l t e r
3. D if f e r e n t ia t o r
4. C o m p a ra to r, T im e D o m a in F ilt e r , a n d
D ig it iz e r
a n d L in e a r P hase
FIGURE 4-9
READ BLOCK DIAGRAM
T h e R e a d o n ly c ir c u it s a re used to is o la te th e
re a d a m p lif ie r fr o m
across th e h e a d d u r in g a w r it e o p e ra tio n . T he
sid e s e le c t is u sed to
r e a d /w r ite heads.
T h e o u tp u t s ig n a l fr o m th e r e a d /w r ite h e a d is
a m p lifie d b y a re a d a m p lif ie r , a n d f ilt e r e d b y
a lin e a r phase f i l t e r to re m o v e no ise . T h e
lin e a r o u tp u t fr o m th e f i l t e r is passed to th e
d iff e r e n t ia t o r , w h ic h g e n e ra te s a w a v e fo rm
w hose zero crossovers c o rre s p o n d to th e p ea ks
o f th e R ead s ig n a l. T h e n , th is s ig n a l is fe d to a
c o m p a ra to r, tim e d o m a in f i l t e r , a n d d ig itiz e r
c ir c u it r y . S u b s e q u e n tly , th e s ig n a l is s u p p lie d
to th e L S I c h ip , th e n to th e in te rfa c e .
4-9
th e v o lta g e e x c u rs io n
e n a b le one o f th e