Atari 130XE - S/N A1 1122117
18 September 2016
When the system is switched on, the power indicator lights and the display monitor indicates it has a signal, but there is only a blank, black screen. The built-in memory failure diagnostic display does not start.
One or more of the Micron 4264-20 DRAM chips have failed. Replace the failed parts with 200ns or faster 4164-type DRAM.
The 130XE needs only the eight chips closest to the edge of the logic board (bank 1) installed to start up. The eight chips closest to the center of the logic board (bank 2) provide extended memory from 64 KB to 128 KB. The "piggyback" technique may or may not allow the machine to progress past the black screen and thereby provide information about which chips in bank 1 have failed. In this case, it did not, even when piggybacking the entire memory bank. All the DRAM was removed from the board, and sixteen 16-pin sockets were installed. By inserting eight known-good DRAMs into bank 1 and substituting the original chips one at a time, five out of sixteen of the original DRAMs were found to cause the black screen symptom, and one was found to cause a blank light-yellow screen. None of the failed parts would allow the built-in diagnostic to execute if installed.