Operator`s manual

E-1
APPENDIX E. CHANGING RAM OR PROM CHIPS
The 21X has 8 sockets for memory chips. Five sockets hold 8K Random Access Memory (RAM) chips
and three hold Programmable Read Only Memory (PROM) chips. Older 21Xs may have two PROM
chips and as few as two RAM chips.
E.1 DISASSEMBLY OF 21X
1. Turn power off, remove the two Phillips
head screws located near the edges of the
front panel of the micrologger. Carefully lift
the micrologger up and away from the
battery pack and disconnect the plastic
power connector.
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-1
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.
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 memory check (Section 1.5). As a
result of this check the 21X displays the status
of the memory chips as a sequence of 1s and
0s, each representing a chip with the status of
chip 1 on the left and 8 on the right; 0 indicates
a bad chip. For example, 11011111 indicates
that chip 3 (Figure E-1) is bad.
To replace a RAM chip carefully pry the old chip
with a small flat 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-1. Before pushing the
chips into the socket, make certain that all pins
are correctly seated. After installing the chip,
check for pins that may be bent or not firmly
seated in the socket. If there is a bent pin,
remove the chip, carefully straighten the pin and
reinstall the chip.