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1
1
ERROR CODES
6.8
PowER SUPPLY
UNIT
I
7.
.
The
Twlsï terminai
using
a
switching
Power
1
§-_ÉçÖu_§§E§§Üu'5RR0R
Supply which
is
housed
in
an
aluminium
case
and
3
DISPLAY
MEMQRY
FAULT
mounted
to
the inside
of
the terminal
at the
6
EPROM CHECKSUM ERROR
rear panel.
The
PSU
is
made
in
two
versions:
230V
AC
+/-
15%
47-63Hz
I
115V
AB
+/-
15%
47-63Hz
Incoming
AC
voltage
from the
power
line
passes
through
an
RFI
filter
designed
to
prevent con-
tamination
of
the
AC
power
line
by
switching
transients
generated
within
the
power
supply.
The
filtered
AC
is
converted
to
DC
by
a
bridge
rectifier
and
is
filtered
stored
in
a
capaci-
v.
7.1.2
REMEDY
7.1.2.1
Error
code
2
EAROM
checksum
error,
indicates that
the
D64
and/or
D65
are
faulty.
NOTE
Check
also the
-23V
control
circuit,
as
this
circuit
may
cause
the malfunction.
tor.
This unregulated
DC
voltage
is
chopped
by
7.1.2.2 Error
code
3
the
switching
element,
Power
MDS
transistor
BUZ
42,
to
about
45kHz.
The
output
from
this
power
Display
Memory
Fault.
The
error
code
3
will
switch
is
passed
through
a
transformer
and
rec-
tified
to
the
different
secondary
output
volta-
ges.
A
feedback
circuit
controls
the
switching
frequency
and
provide
shortcircuit
protection.
The
voltage
adjustment
potentiometer
affects
also
give the
memory
address
information
so
that
the
faulty
memory IC
can
be
identified,
the
read/write
data
informs about the
memory
contents. Information
about
the
memory
contents
is
insignificant
in order to select
the
bad
all
the output voltages,
and
should
be
set
so
imemory IC
during
this test
sequence.
that
+5V
measured
at
the
MLB
connector
(27
pin
7,8
indicates 5.1V).
7
S
E R V
I
C
E
GENERÅL
This
section
suggests
methodes
for
determining
which
circuit
is
faulty
in
a
malfunctioning
unit.
The
primary
objective is to
determine which
sub
assembly (Main
logic
board,
Power
supply, Moni-
t0r
control
board
or the
Keyboard)
is
faulty.
7.1
POWER-UP
SELF TEST
Upon
power-up,
or
when
the
reset
command
is re-
ceived
by
the
terminal,
the
power-up
self test
is
performing
a
check
of
the
following:
EPROM
checksum
(screen
is
blank)
display
memory
Replace
IC
D89
(screen
is
blank)
scratch
pad memory
Replace
IC
D86
To
select
which
one
is faulty,
run the
special
test
program.
3
address
C803
read/write
XX/XX
Replace
IC
D88
3
address
0003
read/write
XX/XX
Replace
IC
D87
3
address
E003
read/write
XX/XX
Replace
IC
D73
3
address
E803
read/write
XX/XX
Replace
IC
D72
3
address
F003
read/write
XX/XX
Replace
IC
D71
3
address
F803
read/write
XX/XX
Replace
IC
D70
7.1.2.3 Error
code
6
Indicates
that
D79
or
D80,
or
both
contains
wrong
data.
Replace
both
EPROM's,
with the
latest
program
version
if
this failure
occurs.
NOTE
The
first
version
of
the
TWIST
terminal
can
not
use
the
same
program
as
the
later
ver-
sion
of
the
terminal.
See
Service
Bulletins
for
further
information.
EARQM
checksum
.
1,2
_fIELD
SELE TEST
DESCRIPTION
Display refresh
RAM,
and
scratchpad
RAM.
If
during
this test,
the
terminal halts
because
the processor
has
determined
that
the
scratch-
pad
RAM
is
at
fault,
no
further testing of
the
terminal
is
performed
but the
keyboard
burn-in
test
will
start
running.
If
any
error is
detected, the
bell
will
ring
five
times
and
the
error
code
will
be
displayed
in the
upper
left
portion of
the screen.
A
special
test
program
for
the
Facit
TWIST
ter-
minal
is available
as
a
"tool" for
the
first
version
of
the
TWIST
terminal
and
will
be
a
part of
the
normal
firmware
when
the
new
etch
revision is
released
to
the production
(MLB
1142 46
10-30).
7.2.1
HANDLING
INSTRUCTION,
FIRST
VERSION
The
special testprogram
is
stored
in
an
2764
EPROM
marked 5536
20
90-01/5
this
EPROM
should
be
inserted at
IC
position
D80
on
the
Main
Logic
Board.
It
is
not necessary
to
remove
the
IC
D79
during the
test.
T
š
s
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