First post, by mima85
- Rank
- Newbie
Hello, this is my first post here. My name is Michel, I write from Switzerland, from the southern italian-speaking part, so excuse me for my engRish 😀.
I'm an IT guy who's also into retrocomputing, I have a quite sizable collection of old machines which I restored and maintain myself and I occasionally attend retrocomputing events with items from my collection. I have a strong connection with music, synthesizers and sound synthesis too. Music is a very important part of my life since tender age and, of course, you make me very happy if you talk to me about the various incarnations of OPL3 (Yamaha, ESS, Crystal, etc...) and the differences in their implementations, the waveshapes of the SID chip or the intrications of analog circuitry in vintage analog synthesizers. No surprise that I lurked this site for a long time on threads about these topics 😀. I have a collection of such staff too and I occasionally shamelessly put myself on Youtube while playing my synths: https://www.youtube.com/@mima85.
I also have a long-time fascination (read: obsession) with hard drives, matter of fact I'm collecting them since the late 90ies and right now I have something around 200-300 drives in my collection. I actually lost count of them 😁.
In the last years I'm "daring" to do some repairs on very old MFM, stepper-driven units. Matter of fact some time ago I was succesful at reviving a couple drives by swapping their ruined platters with other healthy ones and low-level format them with the controller's onboard utility (you know, debug -> g=800:5, the usual stuff).
Now I'm trying to revive one of my old PS/2-30 hard disks. Those WDI-325s are well known in the retrocomputing spaces to suffer from internal contamination. Most believe that it's the seal that gives up, but by opening a couple of ones I found that the actual source of the contamination was not the seal, which was still intact, but a piece of plastic that holds the head stack's flex PCB where the head amplifier chip is soldered, that is going thru a decomposition process.
Check these images:
1) wdi325_1.jpg - Platter contamination
2) wdi325_2.jpg - Details of plastic piece's decomposition
and you can clearly see that. That white dust is the material coming off the plastic piece, and I think that during this process some gases are being produced too, raising the internal pressure, blowing out from the breathing hole and carrying those plastic particles with them. And actually, if you take a look to photo #3 (wdi325_3.jpg - Dusty spot on platter matching the breathing hole/filter) you can clearly see that most of the dust accumulated in the exact same spot on the platter that for years was sitting still under the breathing hole.
Some days ago I picked out from my collection a 60MB WDI-387 hard disk (the voice coil-driven, MCA-attached unit that's used in PS/2-55sx, 70 and other models) which some years ago was already in the verge of dying most probably due to fading out magnetic signals. It had a lot of bad sectors, they were constantly raising and now it reached the point where track 0 became unreadable. So I decided to open it to assess for internal damage and I found two things:
1) There was no actual physical damage to the platters (that's why I'm thinking about fading-out magnetic signals)
2) Platters were the exact same thickness and iron-oxide coated like the WDI-325's ones.
So I decided to use it as a donor drive and I transplanted two of its three platters to one of my WDI-325 units, the right one in the last photo which is the one I'm trying to revive. I thorougly cleaned the chamber from the dust, cleaned the heads with isopropyl alchool, removed all the dust from the plastic support and covered it with insulating tape to prevent, or at least try to, further particles leaving it and I gave it a spin with my PS/2-30. The drive spun up nicely and, to my suprirse, with the heads pulled toward the platter's outer diameter they were actually able to do a full sweep-in-sweep-out seek, a thing that a WDI-325 drive in working condition would always do at power up (with the heads towards the inner my unit just tries to push them further in for 2-3 times, hitting the stop pin, then it gives up).
Of course the drive was still confused as the layout on those platters, or at least the remainings of it, is from another drive with a completely different geometry, not to mention that the relative alignment between the platters themselves is lost due to me moving them, so the machine unsurprisingly threw out a 1701 error at boot and the disk's LED was blinking a 4-[pause]-4-[pause][...] pattern. As said, all to be expected.
Now comes the part where I want to LLF the drive, and this is where I'm stuck. I tried the PS/2-30 diagnostic disk, I tried speedstor/hardprep, I tried diskmanager both in automatic and manual mode, none of them were succesful. And no, there's no debug -> g=800:5 format routine available as the drive's logic board is an integrated, proto-IDE proprietary IBM controller thatt connects directly to the machine's 8-bit ISA bus. The drive gives signs of life when those programs try to LLF it, it can be heard seeking its heads a handful of times trying to orient itself, but then it gives up and the LLF utility throws whatever error it feels at the moment (bad disk command, disk not ready, unrecognized error, etc...).
This is a stepper drive, so like with any normal MFM stepper drives there should be a manner to low-level format it without specific devices available only for the manufacturer, as no servo orientation signals are required here unlike what happens with voice-coil units. I just want the drive to slam the heads towards the outer stop pin, and step its actuator thru the platters to blast a new geometry onto them regardless of their actual content, like it can be done with normal MFM disks. There should be a manner to do this, perhaps with some obscure software tool or assembly routine that skips the controller's internal data integrity checks: after all when the drive was built in first instance the platters were empty and in some way it had to write down cylinders and sectors on them.
So, after this long post the question is: what I'm missing? There's someone here experienced with those units, who knows specific software tools or procedures to treat this drive like a freshly built unit which needs its initial LLF before leaving the factory?
Thanks to all who'll be eager to help 😀
P.S. The same thread was opened also on hddguru.com, I hope this is not a problem for the site's admins.
