lft
Registered: Jul 2007
Posts: 369 |
Call for data: Interesting 1541 stepper motor behaviour
Hi!
I ran across something interesting on my 1541-II: It appears that the stepper motor magnets are deactivated when the spindle motor is off. At least that's what happens on my particular 1541-II. I'd like to find out if this is true for all drives, so if you have the time, please see if you can reproduce the behaviour described below.
This doesn't seem to be documented in the 1541 schematics and service manual, as far as I can tell. But it could easily be implemented by the PLA chip in the drive.
Here's how to test it:
Load up the 1541 Diagnostic Cartridge V1.0 [ram version]. Press D to read the directory of a disk. This puts the head at track 18. Go to Head Exerciser and press F6 to seek to track 35. Remove the disk and insert the transit card ("head vibration protector"). This will push the head to track 1, and you'll get a feel for how much pressure you need to apply in order to physically push the head around.
However, now the drive has lost track (ha!) of where it is, so hit F8 to exit, insert a disk, then press D to read the directory again. Then go to Head Exerciser and press F6. (It is important that you re-read the directory, otherwise F6 will do nothing here, because the drive will think it's still at track 35.) Remove the disk. Now press F5 to turn on the spindle motor, and try to insert the transit card again. Be careful and don't push too hard, or you might damage the card or the drive. Notice that it doesn't work this time! The card will stick out about 1 cm. This suggests that the stepper magnets were off before, and are active now, pushing back at you.
Finally, while applying a reasonable amount of pressure to the transit card, press F7 to stop the motor. The resistance should suddenly yield, allowing the card to be inserted.
I'm looking forward to your test results! If this behaviour is reliable across all drive versions, then trackloaders probably don't need to verify that they're still on the right track after a disk flip, as long as the motor was left running during the flip (as it usually is, nowadays). |
