Commodore 1571 - Page 32

1571/C128D ALIGNMENT/REPAIR TEST
VERSION 1.2.1
+ — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — — —
| 1571 STEPPER MOTOR CONTROL LOGIC — BASIC CHART 1 |
+--------------+
-------------- +-------------------+-------------------+ ------------------------------------------ +
STP 0
DISPLAY
STP 1
DISPLAY
CHECK IC
PINS
EXPECTED
SIGNAL
INCORRECT
PROBABLE
SIGNAL
FAILURE
0
0
U7
—
25,28 0
VDC
SEE
ADVANCED CHART 1
0
0
U7
-
24,27
+5
VDC
SEE
ADVANCED CHART 1
0 1
U7 24,27 0
VDC
SEE
ADVANCED CHART 1
0
1
U7
-
25,28
+5
VDC SEE
ADVANCED CHART 1
1
0
U7 24,25 0 VDC
SEE
ADVANCED CHART 1
1
0
U7
-
27,28 +5
VDC SEE
ADVANCED CHART 1
1
1
U7
_
24,25 +5
VDC SEE
ADVANCED CHART 1
1
1
U7
-
27,28
0
VDC SEE
ADVANCED CHART 1
+--------------+
-------------- +-------------------+-------------------+ ------------------------------------------ +
* SIGNALS FROM BASIC CHART 2 MUST BE MEASURED WHILE ONE OF THE KEYS,
( + ) OR (-), IS BEING HELD DOWN AND THE READ/WRITE HEAD IS STEPPING
+------------------------------------------------------------------------------------------------------------------- +
| 1571 STEPPER MOTOR CONTROL LOGIC — BASIC CHART 2 |
+
-------------------- +------------------------------------------------------------+ ------------------------------- ++ -------------------- +------------------------------------------------------------+ ------------------------------- +
CHECK
EXPECTED
INCORRECT SIGNAL
CONNECTOR
SIGNAL
PROBABLE FAILURE
— — + - — — — — — — — — — — — — — — — — + — — — — - — — - +
| CN5 - PIN 1 | +5 VDC LEVEL WITH +12 VDC LEVEL PULSE|SEE ADVANCED CHART 2|
+
------------- +-----------------------------------------+ --------------------- +
* IF ALL BASIC SIGNALS ARE CORRECT AND THE HEAD STILL DOES NOT STEP,
A DEFECTIVE DRIVE MECHANISM IS NORMALLY INDICATED
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