Tandy 1400LT Service Manual page 139

lCheck
P i n 4 8 1
'C hec k
IC55,
STEPG5 ( P i n 4 7
of
GATE5)
D I R E C G 5 ( P i n 4 6
of
GATES)
FDC37
( P i n 3 7 o f IC54)
a n d
FDC39 ( P i n 3 9 of IC54)
lof GATE5.
I
Check IC54
a n d IC55
1
Check I C 3 .
Check t h e STEP/ (5. 25)
s i g n a l ( P i n 5 of IC55)
1
a n d DIRECTION/ (5. 25)
I s i g n a l ( ~ i n 3
of '1c55j
1
P e r f o r m
a WRITE o p e r a t i o n
Check WRITE DATA/ (5. 25)
s i g n a l ( P i n 7 of IC55)
I
I
5-30