Tandon alignment

What I tried

Swapped the two full-height Tandons between machines until the problem followed one drive. Then followed the classic-computers.org.nz TM100 procedure: scope on the analog test points on the drive’s logic board, head parked on a track and reading continuously, adjust the head cam.

To park the head I wrote a small program in DEBUG with a 100 that seeks to a track and reads it in a loop. I made the track number a variable so I could move between tracks without leaving the session.

What I measured

Signal amplitude at the test points on the Siglent, on the tracks the procedure calls for. The numbers came out near what the website says they should be.

What broke or surprised me

The DEBUG loop only tells me the head is reading. It can’t tell me which track is actually under the head. I wrote a spec for a proper DOS tool that uses the FDC Read ID command for that and sweeps every track for read reliability.

Next

The aligned drive reads and writes disks from the other drive and from OEM disks. Now the hard drives.