Sage II - CPU Board Troubleshooting; Troubleshooting Hints; CPU Chip Identification

SAGE rI
SERVICE
MANUAL
[1.0]
CPU BOARD
TROUBLESHOOTING
VIII CPU
BOAR,D
TROUBLESHOOTING
:
ilOTE:
Ttrese
procedures
are
intended
for
troubleshooting
a
"dead'l
system.
If the
system
boots
properly,
run
CYCLER,
clean the
disk
heads
etc.
before
startlng
thls
checkout.
When
the
power
ls
turned
on
or the reset
button
ls
pressed,
a
ttdead"
system
sends
no
output
to
the
termlnal
(except
perhaps
a
couple
of
G@
slgns)
and
stops
with
the
processor
LED
set
RED,
Most
fleld problems
are
due to
the
not
properly
seaEed
ln its
socket.
any
of
several
different
problems.
the
time
refer
to
rhe
CHECKLIST
manual.
fallure
of a
chip
or a
chtp
that is
Intermittent
operatlon
may
be
due to
If the
system
wtll
operate
most of
FOR intermittence
sectlon
of
thls
l,lhen
troubleshooting
a
"deadtt
system
experlenced
factory
technicians
:
keep
ln
urind these
hints
from
our
1.
2.
3.
4.
5.
6.
7.
TROUBLESHOOTING
HIf,TS :
Faulty
CPUs are
very
rare.
Faulty
EPROI'1s
are falrly
common.
Faulty
RAl,l chlps
are fairly
common.
A
faulty
RAM
cannot keep
the
system
from
glvlng
a
slgn-on
message.
A
faulty
EPROM
wt1l"
do lt
all
most every
tlme.
Faulty
delay
llnes
do
occur.
Faulty
chlps ln the
Tl
0
section
are
rare.
Faulty
capacitors
may work
for
awhile
but
eventually
degrade
and
cause intermlttent
problems.
These
parts
and
RAM
should
not
effect
the
sign-on
message:
U3
Rn2
u31
u2l
RNl
u63
u49
U5
u10
u62
U6
u73
u11
u46
u7
u74
UT2
u40
U8
v2
RN5
u30
u39
v29
RN4
v23
u58
u20
RN3
u64
u59
u28
Even
a
"dead"
system
will
have
slgnal
actlvity
for
a
short
tlrne
after
reset
is
pressed.
A
scope
probe
can
be
used
Eo
examLne
all
clata,
address,
and
control-
1lnes.
start wlth
the
PR0M slgnals
a8
thls
code ls
the flrst
to
execute"
Check
the
T/O
section
last
even
lf
the
slgnals
there
l-ook
suspect.
It
ls
very
unllkely
that
the
problem
1s ln
th;
I/
O
as
the
cpu
has
no
interactlon
with
this
sectlon
untll
much
later
ln
the
BOOT
routl-ne.
15