Commodore 1571 - Page 35

1571/C128D ALIGNMENT/REPAIR TEST
VERSION 1.2.1
C128D STEPPER
MOTOR CONTROL LOGIC — BASIC CHART !
X X
L
STP 0
DISPLAY
STP 1 1 CHECK
DISPLAY | PINS
IC
EXPECTED
SIGNAL
INCORRECT SIGNAL
PROBABLE FAILURE
0 0
U109
_
12,14
+5 VDC
SEE ADVANCED CHART 1
0
0
U109
-
13,15 +1 VDC
SEE
ANVANCED CHART 1
0
1
U109
13,15 +5 VDC
SEE
ADVANCED CHART 1
0
1
UI09
- 12,14
+1 VDC
SEE
ADVANCED CHART 1
1
0
U109
_
13,14 +5 VDC
SEE
ADVANCED
CHART 1
1
0
U109
-
12,15 +1 VDC
SEE
ADVANCED
CHART 1
1
1
U109
_
12,15 +5
VDC
SEE ADVANCED CHART 1
1
1
U109
-
13,14 +1
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
+
+
C128D STEPPER CONTROL LOGIC -- BASIC CHART 2
+
--------------- +
I CHECK I
I CONNECTOR |
+
--------------- +
| CN15 - PIN 1|
+ --------------- +
EXPECTED
SIGNAL
+
----------------------- +
INCORRECT SIGNAL I
PROBABLE FAILURE |
,+
--------------------- +
+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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