Atari CX - Page 60

Black Screen Troubleshooting (Cont.)
I
Is there a data
signal on Pin 14
of U18-U25?
I
I Yes
Swapout
1) Ul4
2) U15
3) U16
4) U17
J
Is there a data signal
on Pin2of U18-U25?
I
Yes Is there a good
- display?
I
b
P
Open Trace RAM
chip Pin 2 to U2
Or
replace defective RAM.
No
'
Defective:
1 ) U28 (CAO 18087'only)
2) L4-L6
n
+'
4) Open Address I
4
Repair
I line to RA,M 1
Yes
I
a b
Repair or Replace
e
1 b
is there a good
display?
I
Swapout U18-U25
4+
If only one chip is
missing signal, replace
that chip. If not,
I
proceed.
I
B Yes
Does unit function?
I
Is there 4V p-p signal
on Pin
6 of U28?
1 Yes
Is there
a 4V p-p
signal on
Pin 4 of
U18
- U25?
Paae 4-8
Swapout
1) Ul4
2) U28 or Open Pin 4
of
RAM chip(s) to
Pin
8 of U14
Defective:
1
i;fcL6
1
3) C30-33
A Repair J
or
Replace
w
c
If you are servicing a unit containing
PCB CA020108, chip designators have
been changed
from U to A.
CX5200 Field Service Manual