That's probably it. The drive is not stuck, so I'll put it on the MFM tester later this week and see what's up. Does the adapter board have its' own power supply? I'm guessing it's a Shugart SA1000 to MFM interface card. On the bottom side of it it says "Perq systems", that, the little stack of washers to offset it from the drive, and the numerous wire hacks on the board mark it as yet another product from the mighty Three Rivers company :-) God my shed is getting full.... C On 1/18/2021 4:44 PM, Mattis Lind wrote:

On Mon, Jan 18, 2021 at 10:22 PM Chris Zach via cctalk <cctalk at classiccmp.org> wrote: Yes it does. It's the little white 3-pin connector on the board. From memory it's +5V, ground, -5V but do check that before powering up. A word of warning. These boards (known as 'DIB's (Disk Interface Board)) use totem-pole devices to drive the disk drive signals. If you power up the drive with this board connected but unpowered it has the annoying trick of driving said lines low. Which means write gate is asserted. Which in turn means the boot track gets corrupted. Do not ask how I found that out, Alas not. The interface back to the PERQ EIO board (the 50 pin cable) is sort-of the same signals as the SA4000, but not quite. As some of the signals were controlled by software (microcode actually) they could be re-assigned. The SA4000 has a step and direction pair of signals to move the heads. IIRC with this interface board you can load a value into a register on the board and it'll move the heads that many cylinders. It also does some of the very low level MFM encoding and decoding, clock separation, etc. The 5.25" drive DIB is covered in the PERQ 2 schematics book which I assume you've looked at. -tony