Commodore 1571 - Page 41

1571/C128D ALIGNMENT/REPAIR TEST
VERSION 1.2.1
C1-28D DATA BUS WRITE CHART
CHECK FOR DATA LINES HELD HIGH
--- INPUT HEX CODE '00'
DATA BUS
DISPLAY
CHECK IC
PINS
EXPECTED
SIGNAL
SCOPE
MODE
INCORRECT SIGNAL
PROBABLE FAILURE
00000000
00000000
00000000
00000000
U104 - 2,3,4,5
6,7,8,9
U105 - 35
U113 - 8
Ulll - 6
LOW
LOW
LOW
HIGH
DC
DC
DC
DC
U104 - U105
U105 - U113 - Ulll
U113 - Ulll
Ulll - U108
DATA BUS
DISPLAY
CHECK 1 EXPECTED
CONNECTOR | SIGNAL
SCOPE I INCORRECT SIGNAL
MODE [ PROBABLE FAILURE
00000000 | CN12 - 1,9 | 0 V ANALOG | AC | U108 - BAD DRIVE
CHECK FOR DATA LINES HELD LOW
--- INPUT HEX CODE 'FF'
NOTE: HEX 'FF' DATA IS APPROXIMENTLY DOUBLE HEX '55' DATA
X X X X
DATA BUS
DISPLAY
CHECK IC
PINS
EXPECTED
SIGNAL
SCOPE
MODE
INCORRECT SIGNAL
PROBABLE FAILURE
11111111
11111111
11111111
11111111
U104 - 2,3,4,5
6,7,8,9
U105 - 35
U113 - 8
Ulll - 6
HIGH
SERIAL DATA
SERIAL DATA
SERIAL DATA
DC
DC
DC
DC
U104 - U105
U105 - U113 - Ulll
U113 - Ulll
Ulll - U108
DATA BUS
DISPLAY
CHECK
CONNECTOR
EXPECTED
SIGNAL
SCOPE
MODE
INCORRECT SIGNAL
PROBABLE FAILURE
11111111 | CN12 - 1,9
ANALOG DATA | AC
.+
--------------- + -------- + ---------------------------- +
| U108 - BAD DRIVE |
CHECK FOR ALTERNATING DATA LINES
--- INPUT HEX CODE '55'
NOTE: HEX '55' DATA IS APPROXIMENTLY HALF HEX 'FF* DATA
----- + --------------- +--------------+ ------- +-------------------------
DATA BUS
CHECK IC EXPECTED
SCOPE
INCORRECT SIGNAL
DISPLAY
PINS
SIGNAL
MODE
PROBABLE FAILURE
01010101 U104 - 2,4,6,8
HIGH DC
U104 - U105
01010101
U104 - 3,5,7,9
LOW
DC
U104 - U105
01010101
U105 - 35
SERIAL DATA DC
U105 - U113 - Ulll
01010101
U113 - 8
SERIAL DATA
DC
U113 - Ulll
01010101
Ulll - 6
SERIAL DATA
DC
Ulll - U108
DATA BUS CHECK
EXPECTED
SCOPE
INCORRECT SIGNAL
DISPLAY
CONNECTOR SIGNAL
MODE
PROBABLE FAILURE
I
I
01010101
CN12 - 1,9
ANALOG DATA |
-------------+.
AC
U108 - BAD DRIVE |
----------------------+
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