Horizontal
and
Vertical
Adjustment
After
components
in
the
Sync
Generator
are
replaced
or
after
other
repair work,
the
hori-
zontal
and
vertical centering shou
Id
be con-
firmed.
Enter
the
following sample program:
1.0
CLS
2.0 FOR
X=.0
TO
127
3.0
SET
( X,
.0
)
:
SET
(X,47)
4.0 NEXT X
5.0
FOR
Y=.0
TO
47
6.0
SET
(
.0
, Y )
SET(127,X)
7.0
NEXT Y
8.0
FOR X
=
62
TO
65
9.0
SET
(X,23)
:
SET
(X,24)
1.0.0
NEXT
X
11.0
GO
TO
11.0
You can load
th
is
program
on
a
tape
several
times
(for easy use). It will run
on
both
Level I
and Level II machines.
The
re-centering program draws a large graphics
rectangle
on
the
outside
boundaries
of
the
cell
array. It also draws a
center
rectangle. Adjust
R20
and
R21 so
that
there
are equal boundaries
on
all
sides
of
the
large rectangle. Use a non-
metallic screwdriver so
body
capacitance
does
not
interfere with
your
adjustments.
76
It Doesn't Work
......
Sometimes
There
is
a well
known
rule
of
Murphy's
Law
that
states:
"A
device will
function
properly
when-
ever
the
operator
is
in
a position
to
correct
a
malfunction".
There
may
come
a
time
when you find
your
TRS-80
operates
just
great when it
comes
near
a
test
bench.
But
when
the
moon
is
just
right
and
the
Computer
is
away from
the
schematics
and
test
equipment,
the
memory
listing looks
like
some
unknown
language and
the
Relay
keeps
time
with
the
garbage
.on
the
display.
The
only
logical
choice
you have
is
to
burn
it in.
Set
up
the
computer
in
some
unused
corner
and
run
the
memory
part
of
SCQATS. Hopefully,
after
a few hours, SCQATS will
root
out
a
spastic
memory
location.
Try
to
keep
the
unit
in
the
case
for
maximum
heat
retention.
If
all
else
fails, replace
the
RAMs as a set. Maybe replacing
an
entire
set
of
RAMs will be less costly
on
your
nerves
than
fighting a losing war with
one
bit.
If
the
problem appears
to
be
in
some
other
sec-
tion
where SCQA
TS
is
not
effective,
try
to
gen-
erate
a program
that
will cause a
constant
failure.
The
only
chance
you have
to
fix an
erratic
problem
is
a faithfu I duplication
of
the
malfunction.
If
the
problem
is:
For/loop
state-
ments
crash
part
of
the
video
section,
then
use
For/loop
commands
in
your
program.
Maybe
there
is
a cold solder
joint
that
opens
every
once
in
a while.
Expect
one
of
these
when
you
find a
problem
that
exists
only
if
you
flex
the
Board a
certain
way. See if you can localize
the
bad
joint
by
tapping
the
Board with a non-
conductive
rod. Maybe you have a solder ball
rolling
around.
Sometimes
you can jar it
out
from
under
a
socket
by
tapping
the
Board. If
you're
lucky,
the
ball
may
lodge somewhere and
stay. Once
you've
got
the
problem
to
stay still,
you've
almost
got
it
fixed.
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