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Kaypro 2 - 06-01.TIFF

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The
fOllowing
sections
contain
schematics,
chip
layout
diagrams,
and
IC
lists
(by
U-number)
fOr
Kaypro
mainboards.
This
is
not
intended
to
be
a
theory
of
operation,
but
rather
an
aid
to
locating
possible
problems
on
a .mai.nl::x>ard.
;
,.
Consult
an
appropriate
databJok
(TrL,
Zilog,
etc.)
if
you
need
to
find
out
the
internal
v.orkings
of
a
particular
IC.
MAINBQl\RD .TRaJBLEsHoorING
TIPS:
A
blank
EPRCM
can
be
used
to
help
troubleshoot
Kaypro
mainlx:>ards
of
series
81-110, 81-240,
and
81-180.
The
appropriate
model
of
EPRCM
(2732,
2716,
etc)
allows
a
quick
check
of
the
1:x:lard.
It
will
usually
fOrce
the
data
and
address
lines
to
toggle
at
approximately
the
same
amplitude,
allowing
the
technician
to
use
a
scope
to
spot
affected
lines.
If
the
video
display
does
not
show
a
screen
filled
with
alternating
"9'''s
and
apostrophes,
you
have
a
problem
in
the
video
RAM
or
associated
circuitry.
You
can
check
the
main
RAM
and
associated
circuitry
quickly
with
a
scope
by
looking
at
pin
14
on
each
of
the
RAM
chips.
There
should
be
a
pattern
of
signals
like
this:
For
th~
81-240
1:x:lard:
U20
(D7)
U21
(06)
U22 (D5)
U23 (D4)
U24 (D3)
U25
(D2)
U26
(Dl)
U27
(00)
ION
ION
toggle
toggle
toggle
ION
ION
toggle
The
U-numbers
0 f
the
main
RAM
chips
will
vary
depending
on
which
mai.nl::x>ard
you
have,
but
the
pattern
will
be
the
same.
6-1

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