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Mac SE Miniscribe Issue

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Mac SE Miniscribe Issue

by falbs » Mon Jul 28, 2014 2:27 pm


Over the past few months I've been restoring a Mac SE I saved 20-odd years ago when I was a teenage programmer doing some part-time work for a publishing company who was dumping gear. I ended up with the SE as it was only one I could carry home with me (as I didn't then have a car) and it sat around doing nothing this whole time, having surviving several house moves.

The SE still has it's original Miniscribe 8425SA HDD on which I installed System 6.0.8 off diskette that boots fine (and sounds great). However, every time I try to write to an area of the disk past 6.612Mb the drive freaks-out with the stepper motor seeking back and forward for ~4 seconds, resulting in System reporting a disk error and the write failing. As the machine doesn't lock up I can just wait a few seconds for the drive to gather itself and I can continue on, but I still can't get past this barrier.
In my research on the Internet, I can't seem to find anyone who has documented this particular issue with this model Miniscribe. It appears if people can get past the stiction issue, the drives are fairly reliable.

Would this behaviour be indicative of physical damage (or possibly degradation) of the platters?

If the platters are damaged or degrading, I guess ideally I would need to find a 3.5" SCSI-1 drive from somewhere which is now seemingly a challenge in itself. I do have some 9Gb LVD drives around, but would I right in thinking I have to do some high-bit termination in addition to obtaining an LVD to SCSI-1 adaptor to get such a drive to run on the SE (assuming the PSU could handle the power requirement)?

I hope this has turned out OK as a first post. I've never really taken to discussion Forums in the past usually preferring to figure stuff out myself or hassling colleagues directly. However I've recently found people's recollection of this old machinery is now becoming quite hazy and parts very scarce, highlighting the importance of these forums.

Thanks for any help anyone can provide!


Steven Falvey
Posts: 2
Joined: Fri Jul 25, 2014 2:51 pm

Re: Mac SE Miniscribe Issue

by mrad01 » Mon Jul 28, 2014 7:19 pm

I've "restored"a number of SEs and SE/30s over the years. When you get the drives doing that - generally it is game over. Sometimes you can use a drive formatting tool like FWB Hard Disk Toolkit to remap bad blocks - but it depends.

I have bought SCSI-1 disks off eBay and installed them into my SEs and SE/30s. Never had much luck with SCSI-II upward - or any 68-way to 50 pin conversions in the SE.

The SE PSU would manage with a LVD disk - it's the SCSI controller (and OS) which will be the issue.
Posts: 289
Joined: Sun Sep 16, 2012 6:13 pm

Re: Mac SE Miniscribe Issue

by falbs » Tue Jul 29, 2014 11:05 am

Thanks for the tip - I'll give FWB Toolkit a go, then visit eBay.

In the scheme of things, this hard drive has ended up being a reasonably minor problem. I initially had to shake out a few issues with the flyback circuit - luckily there seems to be a lot of circuit information on the internet which made diagnosis a lot easier.
On getting the machine to display something I had a few issues with the memory, which the local mac user group was able to help diagnose. I had a few intermittent faults with the logic board after that, but a thorough clean of the board seems to have resolved this even though it wasn't noticeably grubby.

Thanks again for the assistance - much appreciated.


Steven F.
Posts: 2
Joined: Fri Jul 25, 2014 2:51 pm

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