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The 21X has
and three ho
chips and as
APPENDIX
E.
CHANGING RAM OR PROM CHIPS
sockets for
memory chips. Five sockets hotd 8K Random
Access
Memory
(An@
9lttps
prigi^^"firc
neid
Onty
tttemory
FROM) chips.
Older
21Xs may have two PROM
'ew
as two RAM
chiPs.
2.
Lay
the micrologger face down
on
a padded
surface. Remove the four Phillips head
screws
from the corners of the aluminum
back plate. Lift the back plate up and away
to expose the 21X CPU
board.
Figure
E-l
shows
the CPU card; the memory chips are
in
the lower right hand
corner.
The
locations numbered
1-5
hold RAM chips.
Locations 8,
7, and 6 hold PROM
chiPs.
E.l
DISASSETI'IBLY OF 21X
1.
Turn
pourcr
off, remove the two Phillips
head
scr4ws located near the edges
of
the
front pan$l of the micrologger. Carefully lift
the microfogger
up
and away from
the
battery
P{ck and disconnect the plastic
power
cofnector.
6
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51 t
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I
P
t:ta
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hN
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i.:,JO
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il
FIGURE
E-1.
Memory
Sockets on
CPU
Card
E,2
INSTALLING NEW RAM CHIPS
The standard 21X has the maximum memory
allowable.
In
the unlikely event that a RAM chip
fails,
the 21X can detect the bad chip during its
power-up mernory check (Section
1.5).
As a
iesult
of
this
OhecktheZlXdisplays the
status
of
the
memoil
chips as a sequence
of 1s and
0s,
each reprfsenting
a
chip with
the status of
chip
1
on the feft and
8
on
the right; 0 indicates
a bad
chip.
flor example, 11011111 indicates
that chip
3 (Flgure
E-l)
is bad.
To replace a RAM chip carefully
pry
the old chip
with a
smallflat
blade screwdriver, start at one
end and
then loosen the other, alternating until
the
chip
is
free.
The new chip should be
installed with
the notched end
in
the same
direction as the other chips, to the right side of
the
card in Figure
E-l.
Before pushing
the
chips into the socket, make certain that
allpins
are
conectly
seated.
After installing the chip,
check
for pins that may be bent or
not
firmly
seated
in
the
socket.
lf there is
a bent pin,
remove
the chip, caretully straighten the pin and
reinstall the
chiP.
E-1
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