Tandy 1400LT Service Manual page 117

@ LCD Check
I s m o n i t o r
s w i t c h o f f ?
~~~
C h e c k p i n 2 5 o f I C 3 0
E " S
s i g n a l
(Low p u l s e
i s o u t p u t f r o m p i n 3 5 of GATE1)
1
Check IC30 a n d G A T E 1
I 1
1
C h e c k t h e LCD r e f e r e n c e v o l t a g e
A.
CN2 :
P i n 1 5 t 5 v
B. CN2 : P i n 1 7
Min. - 1 5 V
++,
o r m a l ?
A : C h e c k
TR1, TR2, P i n l 3 , 1 2
of IC56 a n d P i n 3 1 of GATE3.
B: C h e c k TR10, TR11, P i n 3 9
of
GATE3, R 1 7 , R 1 8 , R 1 9 ,
R20 a n d IC34.
C h e c k
I C 2 8 , I C 2 9 : V i d e o
RAM
I C 2 2 - I C 2 5 a n d I C 2 7
: CGROM
I
C h e c k t h e w a v e f o r m
CN2:Pin10-14
1
ICheck P i n 7 , 9, 14, 16, 181
o f IC33, P i n 1 8 - 2 1 , 5 4
o f IC30.
Q
5-8