Sage II - Page 90

SAGE II SERVICE MANUAL
[1.0]
HARDWARX CHANGES
ON SAGE I I
CHANGES
FROM C80001
To CB0002
(cont)
A
pullup
resistor
was
added to the
IEEE488
(GPIB)
lnterrupt
line.
U66 was
too close to
U67. The can of
U66
(clock)
could
shorE
against
U67, so
U66
was
moved up. When
changing
U66
on
the
CB0001 bend
the
clock
l-ea<ls
so that
U66 sits
away from
V67
sllghtly.
Series damping
reslstors
were added
on signals
BAl, BLz,
BA3 and
AS+.
The CD+
and RG+ remote
port
interrupt
clrcult was
changed.
U59-11
was
connected to
lJ39-21
and
U61-8
was
connected to
U3q-20.
Inputs to
U52
go
through a
dlfferentiator.
Pin
27
became an
optlon
(strap
S05)
on
the
parallel printer
port
and
can
be strapped
elther to +5V
or Ground.
Vari.ous
capacitors
were
repositioned.
the Straps
were
sllkscreened and numbered.
V76
(LS00)
was
added to
allow
the user to
make a
mod
to
allow
extra data
hold
t i.me f
or slow
peripheral
chips.
See
the
mod sheet
of the
schemattcs.
AIso
one
gate
of
tJ76
was
used
for
the
optlonal
mod to allow
ram
to
be the flrst
512K
or the
second
512K.
The
mod sheet
of the
schematl-cs
also shows
a
mod
to free
up
unused
I/
O
ADDFJSS
space which
ls necessary
to use
the C80002 in a SAGE
IV.
The
morl sheet
also
shows
a
mod to allow
addressing
Ehe flrst
128K
to
cause a
Buss
error.
Chassis
ground
was removed
from
the
mounting
hole
whlch
was
closest to
the
power
connector.
The
grounrl
pj-ane
on the front
edge
was
moved back
slightly.
A layout for
an extra
unused
chlp
was
added.
81