Editing Atari 800XE Troubleshooting Guide (section)

=== "Black Screen" (No Boot) Diagnostic Flowchart ===

# '''Verify +5 V''' at the CPU, ANTIC, GTIA, and RAM Vcc pins.
# '''Listen for a brief click or beep''' at power-on. If present, the CPU and OS ROM are likely executing code.
# '''Check the system clock''' — probe pin 39 of the 6502C (Sally) for the 1.77 MHz PAL clock signal using an oscilloscope or frequency counter.
# '''Check the RESET line''' — CPU pin 40 should pulse LOW briefly at power-on, then remain HIGH (+5 V). If stuck LOW, check reset circuit components.
# '''Swap or reseat''' GTIA, ANTIC, CPU (6502C), and POKEY in turn (if socketed).
# '''Reseat or substitute''' OS ROM and BASIC ROM.
# '''Test RAM''' chips (see RAM Fault Diagnosis below).
# '''Inspect for''' shorted decoupling capacitors, burnt resistors, or cracked traces near the power input and bus lines.