Wanted: Old RLL Hard Disk Drive (MiniScribe 8438, Seagate ST-225 or similar)

[n45048]

I'm appealing to the EEVblog community for some assistance.

I'm in the process of refurbishing an old Amstrad PC1512DD XT machine. Part of that is installing a hard disk drive. Since the 1512 doesn't have an on-board hard disk controller, my only option is to install one in the 8-bit ISA slot. I bought an old Western Digital 'FileCard' from eBay which is essentially a WD1002-27X hard disk controller and hard disk mounted on a card.

It appears that the hard disk is faulty. I'm getting error 1701 reported by the controller card which seems to indicate a problem with the primary hard disk.

The hard disk is a MiniScribe 8438 30MB RLL drive. The on-board LED flashes an error code which translated means "Index pulse not detected during spin up". The drive momentarily spins up when power is connected but then spins back down so it sounds to me like a sensor issue. Attempting to repair the disk is probably beyond my level of expertise and I don't really fancy removing the cover anyway.

So basically, I'm looking for a replacement drive. The controller will support "Winchester" drives with up to 16 heads and 1024 cylinders. The drive also must use RLL encoding (MFM is not supported). I've done a quick search on eBay this morning and there are a whole bunch listed, but they are expensive! I am obviously willing to pay if the offer is reasonable or happy to trade for other computer parts and cover the cost of shipping.

Alternatively, I could also use a controller that supports MFM drives (it would need to be an 8-bit ISA card though) and a suitable hard disk drive.

[ozzie72]

Hi, You do not have to remove the cover to check the index sensor, its located under the PC board, I remember the filecards and the 8438  RLL drives. Also the Amstrad 1512. Many years ago I had all the service manuals when I was repairing computers in the day's prior to "throw Away". I have some WD1002A-WX1 or DTC 5160 cards here but no small MFM drives left.

Cheers,
Chris

[Wuerstchenhund]

The drive also must use RLL encoding (MFM is not supported).

You don't really need a RLL drive, most MFM drives should work just fine. Back in the old days I've used plenty of MFM drives with RLL controllers, which also gave you the advantage of increasing the drive's capacity by (if I remember correctly) 50%.

With MFM/RLL, the drives are relatively dumb devices anyways, the encoding is fully determined by the controller.

Just make sure you low-level format the hard disk, which you should do anyways no matter if you use a MFM or RLL drive. This can be done with some low level format utility which came with the controller, or by booting MS DOS and starting debug and then entering:

g=c800:5

which should start the low level format routine built into the controller BIOS.

In addition, just be aware that the Amstrad PC1512 and PC1640 are not 100% XT compatible, which in those days caused me some issues with certain hard disk controller BIOSes.

BTW: if you want to avoid MFM alltogether then search for a Seagate ST-01 or ST-02 hard disk controller which is an ISA 8bit SCSI controller with BIOS. This allows you to use a cheap SCSI hard disk in your PC1512. The difference between ST-01 and ST-02 is that the latter also has a floppy controller but that shouldn't matter.

[n45048]

Hi, You do not have to remove the cover to check the index sensor, its located under the PC board

I pulled the board of and had a quick look, but I didn't really know what I was looking for. I'll take another look over the weekend.

You don't really need a RLL drive, most MFM drives should work just fine.

For some reason the documentation for this particular WD controller specifically stated under no circumstances connect an MFM drive to it. Not sure why, but it was quite clear about it.

I'm happy to try the Seagate SCSI controller as you suggested (it's a matter of finding one with a drive). The reason I went with the WD FileCard is that I know it's compatible with the Amstrad.

[Wuerstchenhund]

For some reason the documentation for this particular WD controller specifically stated under no circumstances connect an MFM drive to it. Not sure why, but it was quite clear about it.

Almost every RLL controller came with such a warning at that time. I guess the reason was that using MFM drives with RLL controllers was unsupported, and they didn't want to deal with that.

I'm happy to try the Seagate SCSI controller as you suggested (it's a matter of finding one with a drive). The reason I went with the WD FileCard is that I know it's compatible with the Amstrad.

I had ST-01's in PC1512's and PC1640, not a problem. Drives aren't an issue, there are tons of SCSI drives on ebay, and you can even use UW/U2W/U3W SCSI drives via a simple adapter. With the latest BIOS (3.3?) ST-01/-2 support 4+GB drives as well.