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Fujitsu M255XK Customer Engineering Manual page 30

5 1/4" mini-flexible disk drive
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3.3.1 TPI and TP2 Pre-Amp (Continued)
TP1 and TP2 are available for checking the characteristics of the Read/Write head
signal.
Figure 3-9 TPl/TP2 Typical Pre-Amp Waveform
3.3.2 TP3 Ground
Used for grounding test instruments. Use care when connecting a probe to TP3 to
prevent shorting nearby test points.
3.3.3 TP4 and TP5 Differential Amp
These test points are used to monitor the output from the Differential Amplifier.
The Differential Amp (like the Pre-Amp and 2nd Amp) also has two 'phase inverted
(180
0 )
outputs that ranges from several tens to several hundreds of millivolts peak-
to-peak. Figure 3-10 shows typical TP1/TP2 Differential Amp Waveforms!
~
/ \
/"f\
. / \
A
Figure 3-10 TP4/TP5 Typical Differential Amp Waveform
For accurate waveform monitoring, a dual trace (2-channeI) oscilloscope should be
used (with one channel set to the inverted ADD input mode) to monitor TP4 and
TP5 as one waveform. The oscilloscope can be grounded at TP3.
TP4 and TP5 are available for checking the overall operation of the read/write
head and amplifiers, and for checking track alignment.
3.3.4 TP6 Erase Gate
Figure 3-10 shows a typical TP6 Waveform. Current is flowing 'in the erase head
at the low level. TP6 is used to check Erase Gate to Write Gate delay
On Delay time
=
262 ±24 microseconds at 1MB (194 ±24 microseconds a,t 1.6MB) ..
Off Delay time = 776 ±24 microseconds at 1MB (524 ±24 microseconds at
1~6MB).
WRIIE GAIE input signal
Erase
gate
On delay
Off deJ..y
Figure 3;..11 TP6 Typical Eraae Gate Waveform
}-12
TS-021.013087 ••• 01

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