Table of Contents
Advertisement
Theory of
Op
er ations
2.4
Test Point Description
Test Point
1·
(Step Pulse);
ST-506 Service Manual
Test Point 1 may be used to monitor the interface step pulses.
Only the
trailing edge of the ,pulse may be considered valid (transition from
negative to positive).
If step puises are issued at a 3.0 millisecond rate,
the signal at Test Point 1 should resemble Figure 3.1.
Test Point
2
(Step Timing);
Test Point 2 may be used to monitor the internal step circuitry.
For
each step pulse on the interface (Test Point 1), two step pulses must be
seen at Test Point 2.
Note that if the Half Step ("H") option is
activated, the second internal pulse will be defeated.
To adjust the internal step circuitry, trigger on Test Point 1 and adjust
R63 for a delay of 2.8 milliseconds (+0.0, ....05) at Test Point 2.
Only
the tr ailing edg e of the pulses may be considered valid. .If step pulses
are issued at a 3.0 millisecond rate, the signal at Test Point
2
should
resemble Figure 3.2.
Test Point
3
(Track Zero Sensod;
Test Point
3
may be used to monitor the Track Zero sensor.
A low logic
level is a valid Track Zero indication.
Test Point
4
Ondex Sensod;
Test Point 4 may be used to monitor the Index sensor.
A highlogic
level is a valid Index indication.
Only the leading edge of the pulse may
be considered valid.
The typical signal at Test Point
4
should resemble
Figure 3.3.
Test Point 4 may be used to adjust the spindle motor speed.
Monitor
Test Point 4 and adjust R3 on the :Motor Control P.C.B. (accessible
through the side frame) for a period of 16.67 milliseconds, ±1%.
Test Point
5
(Seek Complete Timed:
Test Point 5 may be used to monitor the Seek Complete timer.
The
timer should go true approximately 18 milliseconds after the last
interface step pulse is received.
To observe the Seek Complete timer,
trigger on Test Point 1 and monitor the delay at Test Point 5.
Only the
trailing edge of the pulses may be considered valid.
The typical signal
at Test Point 5 should resemble Figure 3.4.
Seagate Teclmology
PAGE 22
5/1/82
Advertisement
Table of Contents
