HP-85 Tapes

[Dave]

I'm trying to get some tapes to work in an HP-85. I have one which works fine which came with the machine I bought. I have 6 of the same type which came with a 9815A machine I have since parted with. The tapes from the 9815 machine all exhibit read errors and don't respond to Ctape or erasetape commands properly (one let me store but couldn't be read back without errors)

any help would be appreciated.

Thanks

Dave