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« Last post by GeoffB17 on Today at 00:42 »
This thread has two separate issues overlapping.
The OP may well now be sorted, I think it's been settled that he's got PCW 9512 format disks that will not read on a 6128, and it's been settled why this is, and he's hoping the get the disks he has correctly formatted, whereupon they may be fine.
The other issue from someone else related to 5.25" disks, and this is less clear.
I have a large number of HD floppies, and these usually work OK, although I've had odd ones that do not, or are not reliable. I have found that HD disks seem to be less reliable than the DD type, both DD disks used on a 360k drive, and also DD disks formatted to 730k (80 track, but still normal density) on an HD (80 track) drive.
Check the following. Hold the disk up to a bright light, so that you can see how near to transparent the magnetic material is. Compare a DD disk, and a HD disk. Looking at the DD disk, the material should appear totally, or near totally, NOT-transparent. With the HD type, depending on the approx date of manufacturer, the material will appear much more transparent than the DD disks, and in some cases VERY transparent.
As I understand it, the 1.2 Mb drives default to using the HD format, and they will try to do so unless they are explicitly told otherwise. There may well be jumpers on the drive to set this, so you COULD alter the jumper setting to force the default to 360k if required. There is no autodetect on the actual disks (unlike the situation with the 3.5" disks).
The big problem will be that the margin of error for the reading/writing is far smaller at the best of times given the thin-ness of the material, so it will not take much to cause the disks to fail. If the same disks are failing on different drives, this does suggest that the acual disks have a problem, but I'm not sure why this might be if they once DID work. But, what might have happened to them in the meantime, if they've since been formatted as DD, or on a 40 track drive, then this (wrong) format could webb be causing a problem because the 80 track format being put on top is not capable of overwriting the 40t format, you need to do the job with a magnet, and maybe a number of times.
The only thing I might suggest, if you MUST use these disks, would be to send me one so that I can try one, on the drives I have, and compare with HD disks I have which do work, and if the disk will NOT work (as you describe) check my methods (and my magnet) and see if I CAN get it to work. Also, I could send you a couple of known OK HD disks to see what THEY do on your drives.
Geoff
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