IIrc the unidisk had some small complatibility issues, i wonder if this is the case with u, check rubywand's FAQ on the net to see if im right....

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You might be thinking of the DuoDisk, which requires a capacitor to be snipped out in order to avoid an issue which would cause it to trash disks.
My recommendation is to buy a Super Serial Card from an Apple II user. You should be able to get one for less than $10, and maybe even less than that. They are super-common. You could post a WTB on comp.sys.apple2.marketplace and have one by next week.