Sharp MZ-80B Service Manual

• Display Block
DO
-
I
Bus driver
07
-
AD
Al 1
0
cso
SOC
VGAT
Whole rever
H
E
se
~
I
Problem
CSOO
No sync. signal
I
No video signal
wFi-
\
/
Characters displayed but
position abnormal
\
Character generator
Vide
-/
Shift
register
Sync
/ ';".,
o signal
. signal
'----
-
Video RAM
L--
lr
Oscillator
V
Oisplay controller
f------
circuit
Address selector
~
I
Block Diagram around Video RAM
....
....
.... ,
Check Point
.
Is the correct signal present at pins 12 and 13 of IC36 ?
Yes:
Check IC36.
No: Check IC42 and I C43 and around them.
(In particular, check if the input of 8MHz, 16MHz
and other clocks are correct (Wave form is shown
on page 15.))
Is pin 16 of IC42 at a high level'
No:
Check
IC23.
Yes:
Proceed to the following.
:
Is a video signal present at pin 8 of IC46?
Yes:
Check IC31, IC33 and IC36.
No:
Check
IC42 and IC43 and around them.
(In particular, check if the input of 8MHz and
16MHz and other clocks are correct (Wave form is
shown on page 15.))
Is the signal at pins 3, 6,10 and 13 of IC37, IC38 and IC39
correct?
Yes:
Check the address of IC41 and the signals of IC37,
38 and 39 connected to it.
-9-

Sharp MZ-80B Specifications

General

Brand	Sharp
Model	MZ-80B
Category	Desktop
Language	English