Sharp MZ-80B Service Manual page 14

• Clock! Audio Block
07
I
DO
,
-I
IRO
Programmable
counter
18253)
CS
GO
Al
Gl
AD
-cc
',,'
"
-~;
troblem,. .,;, •..
Clock tunction is
abnormal.
Audio output is
abnormal.
~
31.25kHz
07
I
DO
IRO
IWR
CS
Peripheral
interface
182551
PC2
Counter #0, #1,
eset signal
,
Al
AD
RESET
Block Diagram around Clock! Audio Block
.'
.
'
....
'
" Check Point
-
Is there a 31.25kHz signal present at pin 9 of
IC19 ?
Yes:
Check IC19 (8253) and around it.
No:
Check IC42 and around it.
Is an output signal present at pin 4 of IC31?
Audio output
.>~;
Yes:
Check amplifier section in the display board.
No:
Check IC23, IC31
-12 -