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.. etc. ) rather than the RAM itself. I verified that ROM HIGH - chip 342-0352-A. ROM LOW - chip 342-0353-A, IWM - chip 34-0043A are in the correct slots and oriented correctly in their sockets. All pins are clean and sockets are clean. I have a known good board and swapped out good ROMs and IWM and still the same problem on the troubled board. The swapped good ROMs and IWM still produce checkerboard & noisy lines on the troubled board. The problem still persists.
Has anyone run into this specific noisy/speckled checkerboard symptom before, and if so, what ended up being the fix?
Thanks, litriSE
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.. etc. ) rather than the RAM itself. I verified that ROM HIGH - chip 342-0352-A. ROM LOW - chip 342-0353-A, IWM - chip 34-0043A are in the correct slots and oriented correctly in their sockets. All pins are clean and sockets are clean. I have a known good board and swapped out good ROMs and IWM and still the same problem on the troubled board. The swapped good ROMs and IWM still produce checkerboard & noisy lines on the troubled board. The problem still persists.
Has anyone run into this specific noisy/speckled checkerboard symptom before, and if so, what ended up being the fix?
Thanks, litriSE
