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step time - Printable Version

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+---- Thread: step time (/showthread.php?tid=476)

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step time - hwrdmltn - 02-14-2018

In some of my restorations, I have a BASF 5.25 drive SSDD (I believe the DEC Rainbow used these) - my problem is that the drive is the older type stepper, similar in fact to the Disk ][ stepper arrangement, very slow and cumbersome to overcome it's stand-still inertia - it needs more time between steps as is programmable in the WD17XX series chips. Is there any way this timing can be changed through the config file?
Thanks

W1ARQ  Howard


RE: step time - admin - 02-15-2018

No, there is no way through the config file.  The SuperCard Pro can have the step delay and track 0 delay changed, but they are really long right now.  8" floppy drives work with the default delays, and they are really slow.  What makes you think that the step delay is too short?


RE: step time - hwrdmltn - 02-15-2018

(02-15-2018, 12:22 AM)admin Wrote: No, there is no way through the config file.  The SuperCard Pro can have the step delay and track 0 delay changed, but they are really long right now.  8" floppy drives work with the default delays, and they are really slow.  What makes you think that the step delay is too short?

Because when I select alignment mode and change tracks to several tracks from where it is, it misses steps and does not arrive at the expected track, or stepping to track 39 then to 0 does not yield the expected result. Or after a media test or erase disk, the head never makes it back to track 0. OTH sequential stepping in or out works ok.

Thanks


RE: step time - admin - 02-15-2018

Something else is wrong.  When the drive steps to track 0 it will continue to step (forever) until the track 0 sensor is detected.  The delay won't matter, the head would be trying to move until track 0 is found.  This sounds like a drive or power problem.


RE: step time - hwrdmltn - 02-16-2018

I agree about the drive or power problem, but in both cases I eliminated those theories as I checked power while the drive was engaged and stepping, and used a logic probe to determine if trk0 is active and in both cases it is. I believe that this drive (1980 vintage) requires a nearly 20ms step rate when moving to random tracks - something the 8" drives can overcome by virtue that they require 24vdc to overcome inertia and seek times are not speced that low - 8ms track to track, but the r0, r1 values in the 17XX can be set for:
r1,r0 = head track-to-track stepping rates. (all)
r1 r0 1770/3 1772
0 0 6 ms 6 ms
0 1 12 ms 12 ms
1 0 20 ms 2 ms
1 1 30 ms 3 ms
so the SA8XX drive would have to use the 12ms. This BASF with a mere 12v stepper of not high specs says it needs 12ms track to track.
Not a show stopper because the SuperCard does what it is supposed to do. Just an observation, Jim. Appreciate your input.

W1ARQ Howard :-)


RE: step time - SomeGuy - 02-16-2018

What system did this drive come from? Does it work in that system? (if you have the system and it works.)

Have you tried the drive on an MS-DOS machine using ImageDisk? ImageDisk has a command line parameter that will let you choose a different step rate.

I hate to say it, but you probably want to use a better drive with the SCP. Or were you just using the SCP to test the drive?


RE: step time - admin - 02-17-2018

Like I said, the step delay will not matter when the head is moving from anything above track 0 to track 0. If you manually move the head up to the middle of the disk, the SCP will drive the head towards the track 0 sensor until it finds the sensor. It will repeat the step process literally forever until track 0 is found. You can use the editor/analyzer to test this easily. Just set the track to read to be track 20 and click the READ TRACK button. The head will step to track 0 and then to track 20 every time you click the button.


RE: step time - hwrdmltn - 02-20-2018

well it seems to have developed a new trouble - the SCP will not step tp track 0 now, - all drives now have only 39 tracks, and when I start it with no drives connected, it reports two drives connected. Whebn I have one drive driv connected it still reports 2 drives connexted, when I go to do a media test, i'm told there is no index pulse. YOWSA....when it rains it pours. Is there a procedure to re-program the micropic? I think it got corrupted somehow.

Thanks W1ARQ Howard


RE: step time - admin - 02-20-2018

If the board powers up, then the PIC is fine (there is a self test done on power up, including a checksum of the code). It's more likely that you have damaged one of the buffer chips. Look at each of the chips (Huey and Duey) for a burn spot.


RE: step time - hwrdmltn - 02-21-2018

While I see no burn spots, I tend to agree. Are these standard 245 8 bit bidirec buffers that can be had by Mouser or Jameco or Digikey? Thanks