Image Map Image Map
Page 4 of 11 FirstFirst 12345678 ... LastLast
Results 31 to 40 of 105

Thread: Aligning Floppy Drives

  1. #31

    Default

    I'm still trying to understand why one needs a digital scope.
    I used to set the track alignment with a regular 100MHz scope.
    When I had access to alignment disk, I used both the one with the burst and
    the ones with the wondering track.
    Now, if I was looking at the bit streams, I'd use a digital scope.
    As chuck mentioned, azimuth is a different thing. Most drive don't have an adjustment
    for that.
    When I was trying to recover some poorly recorded 5.25 disk, I modified a drive so I could adjust
    the right and left of the head assembly. It didn't help much but was fun to try. It was just that there
    wasn't enough signal recorded on the inner tracks. It may have been an issue with theAnyway timing compensation
    but the signals looked stable, regardless of the data, it was just a really low signal ( it was a double
    density hard sectored disk ). You don't see to many of those.
    Anyway, if you have a drive you don't mind butchering, after you align it, you can make the wondering track
    by putting the hub that the disk centers on, on a lathe and make it a little loose. Mount the floppy so that it
    is off centered. You only want to make it off by about 1/8th to 1/4 track some place.
    Dwight

  2. #32
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    32,222
    Blog Entries
    18

    Default

    I think the DSO is useful if you're not used to looking at a traditional analog scope. A lot of us old guys have developed the skill over the years to watch a trace wander across a screen and remember what we saw. Consider that 300 RPM is only 5 traces per second (200 msec.). If you're not used to it, you might find it disturbing.

    Although I don't own a DSO, I've been considering getting one on and off for quite some time. But I've gotten this far with my Tek 465, so unless a DSO falls into my lap for cheap, I'll probably stick with it. OTOH, a logic analyzer is far superior when you're looking at digital signals...

    I recall that reading a PPU P-counter on a CDC 6600 using a scope took a fair amount of squinting. If you had a hung PPU, that was the only way to figure out where it was hanging. No front panels, blinking lights, etc.

  3. #33
    Join Date
    Dec 2011
    Location
    Dallas, TX
    Posts
    241

    Default

    Quote Originally Posted by Dwight Elvey View Post
    I'm still trying to understand why one needs a digital scope.
    Same here. Especially because great analog scopes have aged much better than the digial scopes of the same vintage. A good analog scope can be had for less than $100; and excellent one for less than $200. If one has the space to store it, a vintage analog scope would be a much better choice than a vintage digital unit.

    Dave

  4. #34

    Default

    Quote Originally Posted by Chuck(G) View Post
    I think the DSO is useful if you're not used to looking at a traditional analog scope. A lot of us old guys have developed the skill over the years to watch a trace wander across a screen and remember what we saw. Consider that 300 RPM is only 5 traces per second (200 msec.). If you're not used to it, you might find it disturbing.

    Although I don't own a DSO, I've been considering getting one on and off for quite some time. But I've gotten this far with my Tek 465, so unless a DSO falls into my lap for cheap, I'll probably stick with it. OTOH, a logic analyzer is far superior when you're looking at digital signals...

    I recall that reading a PPU P-counter on a CDC 6600 using a scope took a fair amount of squinting. If you had a hung PPU, that was the only way to figure out where it was hanging. No front panels, blinking lights, etc.
    The older boat anchor tube scopes had higher persistence. One could still do a lot with the hold-off and delayed sweep. The one thing I miss on most analog scopes is being able to look at negative time. I've been using a 100MHz Leader I got for $75 about 20 years ago.
    I have an HP scope that I mean to fix some day. The trigger is dead. It is a 1740A so mostly just a pile of transistors. I got it cheap as well. It should be relatively easy to trace down.
    Delayed sweep is a must though.
    Dwight

  5. #35
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,306

    Default

    Quote Originally Posted by Chuck(G) View Post
    I think the DSO is useful if you're not used to looking at a traditional analog scope. A lot of us old guys have developed the skill over the years to watch a trace wander across a screen and remember what we saw. Consider that 300 RPM is only 5 traces per second (200 msec.). If you're not used to it, you might find it disturbing.
    To 'show the folks', I put a short video at [here] showing what the main output ("cats eye") of the Dysan 224/2A alignment floppy looks like on an analogue CRO.
    Note: Wait for entire video to download before viewing, otherwise you will get the wrong impression.

    I must retry my DSO. I remember trying it once with the Dysan 224/2A, but could not get a display !

  6. #36
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,306

    Default

    Quote Originally Posted by modem7 View Post
    I must retry my DSO. I remember trying it once with the Dysan 224/2A, but could not get a display !
    Done. Short video at [here].

  7. #37

    Default

    It clearly shows the shutter speed of your camera on the analog scope and clearly shows the effect of sampling noise on an analog signal, with a digital scope.
    I don't see any clear advantage to either.
    Dwight

  8. #38
    Join Date
    May 2006
    Location
    Melbourne, Australia
    Posts
    6,306

    Default

    Quote Originally Posted by Dwight Elvey View Post
    I don't see any clear advantage to either.
    I am happy with either, with a personal preference for the DSO.

  9. #39
    Join Date
    Jan 2007
    Location
    Pacific Northwest, USA
    Posts
    32,222
    Blog Entries
    18

    Default

    My point was that an analog scope would seem to be a bit peculiar and probably harder to read to someone used to a DSO.

    I still remember using an old Tek storage scope. A rack-mount 564 Dual-beam, so you could erase the upper or lower half of the display. It was miles away from what's done with DSOs now. I spent many unhappy hours squinting at the storage display.

  10. #40

    Default

    Quote Originally Posted by modem7 View Post
    Done. Short video at [here].
    modem7,

    Thanks for both of those videos. I now have a better understanding of what the issue would be as far as display goes and why you may have to "remember" a trace on the analog scope.
    Current Wish List: 1. IBM 7531 Industrial Series PC 2. NEC MultiSync XL (JC-2001) Monitor 3. MicroSolutions MatchPoint AND/OR UniDOS card 4. Compaq 14" VGA CRT Monitor (the one that came with the SystemPro). 5. Stacker HW CoProcessor Board MCA BUS. If you have any of the above for sale please PM me. Thank you!

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •