Here is the Adaptec board I mentioned. There are two cables coming from the Winchester Disc, a 20-way data cable and a 34-way control cable, and a 50-way cable going from the Adaptec contoller to the Acorn host adapter underneath which then goes to the BBC micro via the 1MHz bus.
This Adaptec board is an ACB4000, which is an MFM density board. In my other Acorn Winchester Disc, the board is an ACB4000A and my Technomatic Winchester has the RLL density ACB4070 so I think I've got a full set of Adaptec ST-506 controller boards!
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