separated printed circuit boards, the motherboard, the CPU PCB, and
the RAM Memory PCB. Previous Troubleshooting paragraphs, Procedures
One, Two, and Three have already isolated a failing printed circuit
board. The following paragraphs will provide additional information
to isolate the failing integrated circuit (Chips).
RAM MEMORY BOARD
The test results and chip replacement procedures are the same for
either the 8K or 16K RAM Memory boards. Chip replacement for both the
8K board and 16K board will be the same, all boards will be repaired
with 16K chips.
This procedure assumes that the RAM Memory board has already been
cleaned and lubricated according to the procedures outlined in para-
graph 5.2.1. If this has not been doner do so at this time, and rerun
the System Check-Out to verify a failing RAM Memory board.
Before beginning to replace chips, check both 74LS158 chips
(Z503 and Z504) to ensure that they are identical, refer to
Figures 5-12 and 5-13 for reference:
• Same Date Codes
• Same Manufacturer
Figure 5-12. RAM Memory Board Locations, 8K
Review the notes you made during the RAM TEST, rows D and E of the
test indicate which RAM chip was failing during the test, for
example:
ATARI Personal Computers 5-24
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