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Any thoughts on what's wrong with my SE?

Hi,

My SE stopped working properly a few months ago, it won't boot system 6 or 7, freezing on the welcome screen. It can boot System 4 but the mouse doesn't move at all.

I've tried replacing the power supply with an ATX unit that has enough amps for each rail, but still no change in behaviour.

I suspect the fuse on the ADB circuit needs to be replaced, but I'm at a loss as to what would cause the newer systems to freeze, I'm thinking faulty RAM or chips but I honestly don't know.

If anyone has an idea as to what went wrong with it, please let me know

- Bionicle_159
 

Torbar

Well-known member
What are you using as your boot disk. to boot the OS's? (floppy, hard drive, SCSI2SD/BlueSCSI/etc)?
 

LaPorta

Well-known member
If I am correct, System 4 didn't look for the presence of SCSI equipment, 6 and 7 do I think. Somewhere, the SCSI and ADB are somewhat interrelated on the board if I am not mistaken. I'll take a look at some references and see if I can come with anything.
 
What are you using as your boot disk. to boot the OS's? (floppy, hard drive, SCSI2SD/BlueSCSI/etc)?
I've tried my System 6 hard drive and my FloppyEmu.
If I am correct, System 4 didn't look for the presence of SCSI equipment, 6 and 7 do I think. Somewhere, the SCSI and ADB are somewhat interrelated on the board if I am not mistaken. I'll take a look at some references and see if I can come with anything.
If the SCSI bus is broken then I'm not hopeful, it's hard enough finding ROMs and controllers for a decent price :/
 

bdurbrow

Well-known member
The machine must initialize and access the SCSI interface chip in order to scan for a bootable system disc on the SCSI bus. Because it's freezing after that process, I'm suspicious that it's not the SCSI interface chip itself; and this is compounded by the fact that it freezes when booting from a FloppyEmu.

If you disconnect all the devices (SCSI drive, FloppyEmu, etc), do you get a flashing question mark icon; and does it in fact flash?

When it's frozen, if you push the Interrupt switch, do you enter in to the ROM debugger? If so, does typing work? Can you enter the "TD" command and take a screenshot (with your phone, etc) and post that?



The SCSI chip on the SE (and plus, FWIW) is a NCR 5380.

I found this on eBay: https://www.ebay.com/itm/164880421011

This chip would have been used for more than Mac logic boards, so I would expect that there would still be new-old-stock parts out there.
 
The machine must initialize and access the SCSI interface chip in order to scan for a bootable system disc on the SCSI bus. Because it's freezing after that process, I'm suspicious that it's not the SCSI interface chip itself; and this is compounded by the fact that it freezes when booting from a FloppyEmu.

If you disconnect all the devices (SCSI drive, FloppyEmu, etc), do you get a flashing question mark icon; and does it in fact flash?

When it's frozen, if you push the Interrupt switch, do you enter in to the ROM debugger? If so, does typing work? Can you enter the "TD" command and take a screenshot (with your phone, etc) and post that?



The SCSI chip on the SE (and plus, FWIW) is a NCR 5380.

I found this on eBay: https://www.ebay.com/itm/164880421011

This chip would have been used for more than Mac logic boards, so I would expect that there would still be new-old-stock parts out there.
Yep the question mark flashes with no boot device attached.

When it's stuck on welcome and I press the interrupt switch, I tried twice on both ports but I still can't type anything. I think the fuse needs to be dealt with before we move onto debugging.

If it's safe, I can jump the circuit with a bodge wire temporarily.
 

LaPorta

Well-known member
Usually that fuse can be blown by something being incorrectly plugged or unplugged, so it normally would be ok to bypass....provided you do not do anything like that in the meantime! Another thing you can do: just run a continuity check on both ends of the fuse.
 
Usually that fuse can be blown by something being incorrectly plugged or unplugged, so it normally would be ok to bypass....provided you do not do anything like that in the meantime! Another thing you can do: just run a continuity check on both ends of the fuse.
I'll give the fuse a quick check on the multi-meter, just need to find where it is online.
 
I've been using the repair guide by Douglass High, I did a check on the RF choke/fuse and it tested good on each pin, he said there was an additional Pico fuse near it but I'm struggling to find it.

I'm guessing it's either L1 or C12, they don't look like typical fuses but I went over them anyway, L1 has continuity and C12 doesn't.

Could be wrong so I attached an image.
 

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max1zzz

Well-known member
There are no fuses on the ADB circuit on the SE
L1 is a filter inductor, I believe it connects -5V on the mainboard to the I/O area (This is what it dose on the Plus, I don't have the SE schematics to hand right now to verify this on the SE though), C12 is a probably a decoupling cap between +5v and ground
Do not short either of these, sorting C12 in particular could damage the board or your PSU.
 
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