I finally got back to looking at this. Using a logic probe, I can see that the Density Select line is low, as it should be. But, Drive Select 1, Motor Enable 1, Disk Change, and Ready are all high. They should all be low. I tried jumpering Ready to ground at the 8520, but the drive would not come up at all. In what order should the controller pull these lines low in order for the drive to read a disk? On Fri, 17 Apr 2015, David Ross wrote: > It’s been a long time since I did this mod, but I had to put a resistor on the disk change line. I don’t know if any particular value is needed and I don’t have a 1581 to test on anymore. I just grabbed something out of my parts box. > >> On Apr 17, 2015, at 4:32 PM, William Levak <wlevak@SDF.ORG> wrote: >> >> On Sun, 29 Mar 2015, William Levak wrote: >> >>> After lookin through all the specifications on the 1581 and PC connectors, I have concluded that it is not necessary to alter the 1581's system board. All that is necessary is to modify the cable connecting the drive mechanism to the system board. >>> >>> PC 1581 >>> disk change 34 2 >>> density select 2 not available, connect to signal ground >>> (any odd numbered line except 1) >>> >>> Line 3 is not connected on the PC, but it might be on a drive mechanism, so it is best to avoid that line. >>> >>> Lines that are connected to +5V have a pull up resistor; lines that are connected to ground do not, so I do not need a resistor on "density select". >>> >>> In addition, the PC interface has lines for a second drive which are not connected to anything on the 1581, but the corresponding signal grounds are connected to ground (13, 17). The PC does not use lines 4 or 6, but their grounds are connected (5, 7). >>> >>> Line 5 looks like the best choice for grounding "density select". >> >> I have tried several variations on this and it does not work. >> >> Maybe someone out there can see what I am doing wrong. >> >> This is what I have tried: >> >> PC floppy 1581 board >> line 2 ground puts density select in DD >> line 34 line 2 connects PC disk change to 1581 disk change >> line 34 Ready line >> >> I have tried several ways of connecting 1581 line 34 to ground, but the drive says "drive not ready" >> >> Any suggestions? >> >> >> wlevak@sdf.lonestar.org >> SDF Public Access UNIX System - http://sdf.lonestar.org >> >> Message was sent through the cbm-hackers mailing list > > wlevak@sdf.lonestar.org SDF Public Access UNIX System - http://sdf.lonestar.org Message was sent through the cbm-hackers mailing listReceived on 2016-08-20 05:00:03
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