tony359
Active member
Hi all,
The same Macintosh SE I have been discussing here is showing a weird and intermittent fault.
About 50% of times it's powered up, it BONGs, the screen turns on with the grey pattern and about 17 seconds later the pattern gets brighter, I hear a click from the speaker, the mouse pointer shows up and then the system tries to boot up - or the Floppy-Question mark appears if no drives are connected.
The remaining 50% of times the Mac Bongs but the display remains grey forever (I think it's fine diagonal lines rather than the solid grey I see later at boot) no more progress. This happens with no drives connected as well so this is not a drive struggling to come up online.
Notes.
- If I press the debug button when it stalls, I have 0000000F 0000000D which I understand it's the code for "nothing to report".
- If I reset by pressing the reset switch, the system then boots up fine 90% of times. Sometimes it needs another go
- This happens when cold or hot
- I checked the power rails with scope and meter. They seem ok. Reset line starts LOW and 250ms after the voltages are up, it goes HIGH, as it should.
- Once the computer has booted up, it seems fine (but my mouse does not work for now so I cannot test much, see other thread)
- The computer had memory issues at the beginning (corrosion) so I tried downgrading from 4MB to 2MB (changing the jumper as well of course) and swapping SIMMs to make sure it was not a bad memory module.
The intermittent nature of the fault makes it a bit difficult to diagnose. Has anybody seen this happening before? I have researched a bit but I do not see anything about that. The amazing HW manual describes the booting process in details but I do not see any mention of how the process works in between the POST and the BOOT.
Any ideas are welcome!
The same Macintosh SE I have been discussing here is showing a weird and intermittent fault.
About 50% of times it's powered up, it BONGs, the screen turns on with the grey pattern and about 17 seconds later the pattern gets brighter, I hear a click from the speaker, the mouse pointer shows up and then the system tries to boot up - or the Floppy-Question mark appears if no drives are connected.
The remaining 50% of times the Mac Bongs but the display remains grey forever (I think it's fine diagonal lines rather than the solid grey I see later at boot) no more progress. This happens with no drives connected as well so this is not a drive struggling to come up online.
Notes.
- If I press the debug button when it stalls, I have 0000000F 0000000D which I understand it's the code for "nothing to report".
- If I reset by pressing the reset switch, the system then boots up fine 90% of times. Sometimes it needs another go
- This happens when cold or hot
- I checked the power rails with scope and meter. They seem ok. Reset line starts LOW and 250ms after the voltages are up, it goes HIGH, as it should.
- Once the computer has booted up, it seems fine (but my mouse does not work for now so I cannot test much, see other thread)
- The computer had memory issues at the beginning (corrosion) so I tried downgrading from 4MB to 2MB (changing the jumper as well of course) and swapping SIMMs to make sure it was not a bad memory module.
The intermittent nature of the fault makes it a bit difficult to diagnose. Has anybody seen this happening before? I have researched a bit but I do not see anything about that. The amazing HW manual describes the booting process in details but I do not see any mention of how the process works in between the POST and the BOOT.
Any ideas are welcome!