Campbell TGT1, Operator'S Manual

Page: 60 / 64

Appendix I. Changing the 21X's RAM or PROM Chips
I-2
I.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. 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 I-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 I-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.
The earliest 21Xs were shipped with only two 4K RAM chips. Current
software does not check for this condition; if an old 21X is being upgraded to
new software PROMS, five 8K RAM chips (CSI Model number EMX8) should
also be installed.
The older 21X has jumpers at locations M15, W20, and W27 (Figure I-1).
With 8K RAM chips installed, M15 should be jumpered on the right set of pins
and W20 and W27 should be jumpered on the left set of pins.
After changing RAM chips reassemble the 21X, turn on the power and confirm
that the power-up check shows all good RAM.
I.3 Changing PROM Chips
PROMs are installed at locations 6, 7, and 8 in Figure I-1. The procedure for
changing a PROM is the same as for a RAM chip, carefully pry out the old chip
and insert the new one, being certain that the notch on the chip is toward the
close edge of the card and that all pins are correctly seated in the sockets.
In general, the PROM chip with the lowest number is inserted in socket 8 and
the PROM with the highest number in socket 6, but check the documentation
received with the PROM update to be sure.
After changing PROMS, reassemble the 21X and turn on the power. Confirm
that the power-up check indicates that all PROMS and RAM are good. Then
check the signature in the *B Mode to be certain that they match those sent with
the documentation for the PROMS.