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Thread: Kaypro 4/83 questions...

  1. #1

    Default Kaypro 4/83 questions...

    I picked this up from a forum member and it is great. Couple of issues/questions so far:

    Can I read/write the disks from a PC? If so, what tools do I need? I've got a Compaq 486 Deskpro with a 5.25" drive (1.2M/360K) so I'm not sure if that is good enough, or I've got a PC/AT 5170 with both a 1.2M/360K and 360K drives. What I'd like is to be able to read/write a disk image to a PC file and then perhaps use cpmtools or the like to modify the PC file. I could use this to transfer files to/from the system.

    The guy who sold it to me said the B: was a bit hit or miss, but so far B: has been working great. A: will boot CP/M, but I tried to do a "DUMP DUMP.COM" command on it and it would just hang trying. B: did this just fine. I tried on A: a number of times with no luck. Then I found the COPY command and made a copy of the CP/M disk from A: to B:. I expected it to fail, but it worked. I then did a verify which also worked. Then I went back to the dump test and now it works on A: as well. Not sure if it just needed warmup or something else - any ideas on what I can do with drive A: - cleaning? checking anything?

    When either or both drives are accessed, you can see a sight flicker in the screen width perhaps indicating a voltage drop from the additional current of the drives. Is this normal or a capacitor issue I should look at? Also, sometimes you can see the font get a little I don't want to say blurry, but not clear during disk activity as well.

    A third issue is that the drive LED never goes out. Access drive A: and it stays on. Try B: and it will then go out on A, light B:, but then B: stays on even after the motor times out and shuts down. Could that be normal? If not, what should I look at?

    I love the old green display, so crisp!

  2. #2


    As I recall, the drive LED does not go out because Kaypro CP/M never deselects the drive.

    I seem to recall that there was a DOS program to access "external" disk formats, but not sure if it would read/write CP/M files. One problem you have is that the DOS drives are probably 96tpi and if you write Kaypro disks there you'll potentially have trouble reading that on the Kaypro 48tpi drives since the written data is much narrower than the 48tpi heads and the signal-to-noise ratio comes into play.

    Not sure why A: has problems, but it might relate to the location of the file on the disk. If it is too close to the hub (larger track numbers) you might be running into a problem reading those inner tracks. When it hangs, is it continually trying to read the disk, or is it just idle?
    - Doug

  3. #3


    The Kaypro copy utility didn't have a verify disk command that just reads one disk (it does have one that verifies two disks), so I tried to write a quick one that would read all sectors using the BIOS. It steps on every other track so I am assuming that it has tracks 0-79 representing both sides. Also the sector in the BIOS function is 0 biased so sectors 0-39 were readable (10 real sectors x 512 bytes each). I can hear it then stepping on even tracks (0, 2, 4, etc.).

    It seems to hang up near track 21 or 22 for some reason though, there is a delay, but then it does do it without returning an error code.

    Does anyone have the service or technical manual for these drives? They are full height Tandon or something I think. I'm going to pull them and try to lubricate them as they are a bit squeaky.

  4. #4


    I've pulled the drives, they look pretty clean. The head situation is interesting to say the least. The floppy pops over top of the bottom head with looks like a six sided black thing coming up from the bottom and then the top head comes down with the door closing and seems to have to pressure/spring to it. If I am getting marks on disks should I try to carefully clean these with a Q-tip and alcohol? Also, these drives are very squeaky, what places can they be safely lubed with oil or grease?

  5. #5


    It is certainly possible that the heads have accumulated dirt, even just in storage. If the diskettes surface is getting marred, you definitely want to stop using them until you've fixed that - you may be scratching the oxide off the media. Also, old (cheap) media may start to lose oxide, so that can make dirty heads worse.

    I'm not familiar with those particular drives (my Kaypro had Epson drives), but you want to be careful cleaning the heads as to not damage alignment. And while lubricating mechanical parts make certain to keep the oil away from any part that contacts the diskette. The grease tends to harden over the years, so you want to apply just enough oil to soften that - or else clean it all off an re-apply new grease. I'm no expert, but that's what I did to mine to get it working again.
    - Doug

  6. #6


    It seems crazy to me that they would release a system where the drive LED doesn't go out. Did all the Kaypro's do this?

  7. #7


    Well, on (most) 5" drives there is no "head load" solenoid, so with the motor off it really doesn't matter. The motors were typically DC, so turning them off was important.
    - Doug

  8. #8


    I also noticed that when either drive is being accessed, both motors are running - is that also normal?

  9. #9


    Yes, the motors are controlled by a common signal.
    - Doug

  10. #10


    Thanks Doug!


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