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The s i g n a l l e v e l a t t h i s TP i s o p p o s i t e i n phase t o t h a t of t h e TRACK 00
(TOO) o u t p u t s i g n a l .
When t h e head i s on t r a c k 00 o r around t r a c k 00
p o s i t i o n , TP3 goes t o H I G H l e v e l .
The v o l t a g e o f TP3 should be more than
4 V
a t t r a c k
00
and l e s s than
0.5V
a t t r s c k 04 ( 9 6 t p i ) o r a t t r a c k 02 ( 4 8 t p i ) .
4.0V, M i n .
0.5V, Max.
TP3 (Track 00 s e n s o r )
Track
Track 04
02 ( 9 6 t p i )
( 4 8 t p i )
7p_
Track 00
(Fig.217) Typical waveform
of
TP3
Notes:
1.
The TRACK 00 o u t p u t s i g n a l goes t o TRUE (LOW l e v e l ) only when
t h e phase A ( P A ) c o i l o f t h e s t e p p i n g motor i s energized and
t h e d i r e c t i o n l a t c h
i s
s e t t o t h e step-out d i r e c t i o n .
Therefore, t h e l e v e l change timing of t h e
TRACK 00
s i g n a l i s
n o t c o n s i s t e n t with t h a t o f t h e TP3 s i g n a l .
2 . Sense timing of t h e t r a c k 00 p o s i t i o n w i l l change i f you loosen
t h e f i x i n g screws o f t h e PCBA MFD c o n t r o l .
T h i s
i s
because t h a t
t h e t r a c k 00 s e n s o r
i s
mounted on t h e PCBA.
Be s u r e t o r e a d j u s t
t h e t r a c k 00 s e n s o r timing according t o item 3-4-14.
( 4 ) TP4, TP5 ( P r e - a m p l i f i e r )
Test p o i n t t o observe t h e read p r e - a m p l i f i e r o u t p u t s i g n a l s .
The p r e - a m p l i f i e r
has two o u t p u t s
of
t h e o r d e r of s e v e r a l dozen t o
s e v e r a l hundred mVp-p,
and they d i f f e r i n phase by 180° ( o p p o s i t e p h a s e ) .
Both o u t p u t s a r e observed a t TP4 and TP5 r e s p e c t i v e l y .
For an a c c u r a t e
o b s e r v a t i o n of t h e read waveforms, use two channels of an o s c i l l o s c o p e
with one channel s e t t o I n v e r t mode and Add both channels.
Use TP6
( O V )
t e s t p o i n t
for
t h e o s c i l l o s c o p e ground.
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250
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