I have a Macintosh SE 820-0176-B, 1986, 630-4125 logic board that shows a checkerboard pattern with random noise/static (speckled dashes) displayed on boot, with no audio boot chime — just a single speaker click. I've installed the suspect board into a known-good SE chassis (proven analog board, PSU, and BlueSCSI), so the fault stays with the logic board regardless of chassis. I'm running 4MB of RAM (4 SIMMs), and I've confirmed this isn't a RAM issue — I've swapped in multiple different sets of tested, known-good SIMMs (different brands/batches) and get the identical noisy checkerboard every time, including after moving all 4 SIMMs into different physical slots.
The board is very clean — I've inspected the RAM sockets, solder joints, and surrounding traces closely and everything looks great, no visible cracks or corrosion.
Given the fault is consistent across all SIMM combinations/positions and isn't chassis-related, I suspect it may be in shared RAM-adjacent logic (GLU chip 341-0538-A, ROM chips, or the BBU) rather than the RAM itself. Has anyone run into this specific noisy/speckled checkerboard symptom before, and if so, what ended up being the fix?
The board is very clean — I've inspected the RAM sockets, solder joints, and surrounding traces closely and everything looks great, no visible cracks or corrosion.
Given the fault is consistent across all SIMM combinations/positions and isn't chassis-related, I suspect it may be in shared RAM-adjacent logic (GLU chip 341-0538-A, ROM chips, or the BBU) rather than the RAM itself. Has anyone run into this specific noisy/speckled checkerboard symptom before, and if so, what ended up being the fix?
