Hi all,
Figured I would share this one as it does not come up very often.
The other day I got my SE/30 out after it has been sitting for a few months. Turned it on and got the flashing ? disk; so I figured the hard drive had died. Put in a boot floppy and the machine booted just fine, and as suspected there was no HDD shown on the desktop.
I had a spare SCSI2SD so I pulled the machine apart and fitted it. After a fair bit of back and forth with patched versions of disktools plus having to change the vendor ID in the SCSI2SD I finally got it initialised and installed OS 7.5.3. Everything went smoothly and then I figured I would try an old Asante SCSI ethernet adaptor on the machine. No sooner had I plugged it in and turned it on I got a flashing ? disk... again I booted from a floppy and the HDD was not shown on the desktop. Immediately powered down and removed the ethernet adaptor, however I still got the ? disk icon. I then pulled everything apart again, checked all connections and then reassembled. This time I got as far as the 'welcome to MacOS' screen, however shortly after I got a fatal 'BUS ERROR'. Now slightly concerned I blew the SCSI bus up I disassembled it again, checked everything, removed the PRAM battery for about 5 minutes, reassembled and rebooted. This time it worked; so I figured something in the PRAM got corrupted.
Fast forward to 3 days later; turned the machine on like normal, started working away at something and then randomly got another 'BUS ERROR'. I then rebooted only to be greeted by the flashing ? disk. Booted from a floppy, and yet again the hard drive wasn't found.
If you made it this far your probably screaming 'capacitors have failed' however I recapped everything (logic board, analog board, PSU... everything) in this machine 7 months ago. The board was thoroughly washed with a proper aqueous PCB washing solution, rinsed with deionised water and then dried with compressed air. The board itself is pristine and there was zero capacitor residue left behind.
A google search provided a small hint. 99% of problems like this were solved by capacitors, but there was one person who had problems with the SCSI chip itself. They didn't really bother with diagnostics, just launched into replacing the SCSI controller IC which turned out to fix everything. I wasn't super keen on doing this unless necessary as it's a fiddly job and on these older machines there is a fair chance that a pad or trace will be damaged in the process. The hint came from a comment someone made about how the pads were very dirty and it's possible that one had a dry solder joint......
I got out the multimeter and started probing between the SCSI IC and the SCSI header. Lo and behold one of the data lines had a resistance of about ~50kohm. On closer inspection the amount of solder between the chip and pad was minuscule; and after years of heat cycling plus the leaky caps in the past must have resulted in a bad joint. I attempted to reflow it; but without removing the chip it was impossible to clean the pad and the IC contact throughly enough and my ~50kohm turned into infinity. So rather than risk damaging something further by being too brutal I ran a jumper wire from the pin to the SCSI header. Since the jumper wire had to run from one side the board to the other I secured it with some dobs of hot glue here and there; ended up looking pretty neat actually.
Turned it on and everything now works just as it did before. There was nothing wrong with the original hard drive; it was just the SCSI bus failing.
Moral of the story - it's not always the capacitors on these things. It's definitely worth checking the IC's for bad joints; especially if the board had leaky caps in the past like mine.
Figured I would share this one as it does not come up very often.
The other day I got my SE/30 out after it has been sitting for a few months. Turned it on and got the flashing ? disk; so I figured the hard drive had died. Put in a boot floppy and the machine booted just fine, and as suspected there was no HDD shown on the desktop.
I had a spare SCSI2SD so I pulled the machine apart and fitted it. After a fair bit of back and forth with patched versions of disktools plus having to change the vendor ID in the SCSI2SD I finally got it initialised and installed OS 7.5.3. Everything went smoothly and then I figured I would try an old Asante SCSI ethernet adaptor on the machine. No sooner had I plugged it in and turned it on I got a flashing ? disk... again I booted from a floppy and the HDD was not shown on the desktop. Immediately powered down and removed the ethernet adaptor, however I still got the ? disk icon. I then pulled everything apart again, checked all connections and then reassembled. This time I got as far as the 'welcome to MacOS' screen, however shortly after I got a fatal 'BUS ERROR'. Now slightly concerned I blew the SCSI bus up I disassembled it again, checked everything, removed the PRAM battery for about 5 minutes, reassembled and rebooted. This time it worked; so I figured something in the PRAM got corrupted.
Fast forward to 3 days later; turned the machine on like normal, started working away at something and then randomly got another 'BUS ERROR'. I then rebooted only to be greeted by the flashing ? disk. Booted from a floppy, and yet again the hard drive wasn't found.
If you made it this far your probably screaming 'capacitors have failed' however I recapped everything (logic board, analog board, PSU... everything) in this machine 7 months ago. The board was thoroughly washed with a proper aqueous PCB washing solution, rinsed with deionised water and then dried with compressed air. The board itself is pristine and there was zero capacitor residue left behind.
A google search provided a small hint. 99% of problems like this were solved by capacitors, but there was one person who had problems with the SCSI chip itself. They didn't really bother with diagnostics, just launched into replacing the SCSI controller IC which turned out to fix everything. I wasn't super keen on doing this unless necessary as it's a fiddly job and on these older machines there is a fair chance that a pad or trace will be damaged in the process. The hint came from a comment someone made about how the pads were very dirty and it's possible that one had a dry solder joint......
I got out the multimeter and started probing between the SCSI IC and the SCSI header. Lo and behold one of the data lines had a resistance of about ~50kohm. On closer inspection the amount of solder between the chip and pad was minuscule; and after years of heat cycling plus the leaky caps in the past must have resulted in a bad joint. I attempted to reflow it; but without removing the chip it was impossible to clean the pad and the IC contact throughly enough and my ~50kohm turned into infinity. So rather than risk damaging something further by being too brutal I ran a jumper wire from the pin to the SCSI header. Since the jumper wire had to run from one side the board to the other I secured it with some dobs of hot glue here and there; ended up looking pretty neat actually.
Turned it on and everything now works just as it did before. There was nothing wrong with the original hard drive; it was just the SCSI bus failing.
Moral of the story - it's not always the capacitors on these things. It's definitely worth checking the IC's for bad joints; especially if the board had leaky caps in the past like mine.