Hello group,I have a disk ii drive that I can’t set the speed on. I use the Apple dealer disk alignment aid software as I always do. If anyone’s not familiar with this program 0 is in the center representing 300rpm. Either side of the zero will represent positive or negative. It shows a -1500 (which I know is not near accurate). Turning the variable resistor it will jump to +1500. Then bounce back and forth between the two positive and negative extremes without touching the resistor. I’ve replaced the variable resistor, as well as the 3 tantalum capacitors on the board as well as making up a new cable. Turning the potentiometer I can hear the drive IS speeding up and slowing down (It’s clearly not spinning at 1500) but it is responding to adjustments. Kind of at a loss here now as I hoped changing those things would have corrected the issue. Any direction would he greatly appreciated.
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Could be a bad belt. Console5 sells new belts for both Shugart and Alps drives. The Alps one is listed as a Commodore 1541 belt. But I've seen both an Apple and 1541 Alps chassis. They are the same from the spindle motor standpoint (even use the same motor speed board). I see no reason a 1541 Alps belt wouldn't work on an Apple Alps drive.
Unless anyone else has any ideas, that's all I can think of. You could also try some of the other drive speed adjustment programs as well just to confirm the behavior. Most diagnostic software disks have them, as well as Locksmith and Copy II+. Locksmith I believe gives you a visual indicator that accumulates each pass where it believes the speed is. There is also the "look at the sticker on the spindle under a 50hz or 60hz light while it's spinning" method to get a visual indicator of speed.
Can you verify the speed stroboscopically?
Is there a stroboscopic disk printed on the bottom of the spidle (remove the drive's bottom cover)
Using a "strobe" app on your smartphone set to 60 Hz you should be able to dial the speed that way (or at least verify that it's bad).
If your speed is stable using that method you should then look for read/write issues with the drive head circuitry on the drive's analog board.
Or at least you can verify that the speed is totally out to lunch.
I do know that Alps speed control boards have gone bad in the past (the Shugart speed boards never seem to go bad) but you should verify speed mechanically before proceeding.
If you don't have the stroboscopic disk on the spindle, then use a marker and draw a vertical line on the spindle.
Then you can use an "RPM" type camera app on your smarphone set to 300 RPM to verify that the speed is constant (using the app you will see that the line would be stationary on your phone's screen with the RPM app set to 300 RPM)
Measuring the speed mechanically like this is the first thing you should do anyway. The software is just to do the final tweak to what the computer expects.
Both RPM style apps and strobe type apps can be found for free on both the Apple App store or Google Play.
For reference, here is the bottom of a typical Alps type mechanism:
IMG_7402s.JPG
Underneath a Shugart looks like this:
shugart.jpeg
Thanks for the reply’s Baldrick. I appreciate you joining in my threads. The belt looks fine. I cleaned both wheels and I flipped the belt. I did download an app with the strobe and I set the speed with that. My ear wasn’t too far off but still readings are the same. Copy ii plus gives me a reading of 000.6 but nothing is steady. I tried a known good analog board just to say I did and same things. But I expected that. I also changed the analog board because this drive has a problem formatting blanks. And a disk verify shows bad sectors in several known good disks and track zero shows bad on all disks. I’m wondering if this is a read/write head issue?
So I'm going to assume that your speed is stable because you verified it with a strobe app on your smartphone. Or am I missing something? Your explanation isn't all that clear.
Do you still have a speed issue scanning it with your smartphone? If your speed is stable we need to address the read/write problem or track seek problem.
If it's not stable we need to figure out why.
Incidentally, is it an Alps drive or a Shugart drive mechanism?
I’m sorry if I was vague, yes I was able to dial in 300rpms with the app on the phone. This is an Alps drive.
So if the speed is stable then you need to look at the read/write head and the stepper motor mechanism.
A good way to check for smooth stepper motor operation is with Locksmith 6.0 which has a qick format function that can sweep the stepper motor through its range of motion.
Also, I presume that the read / write head on your drive is clean?
Yes the head has been cleaned. I am able to boot disks. The 3.3 system master, copy ii plus etc. just when I go to format the blank with copy ii plus it tells me error writing to track zero and if I try to format after booting the system master using “init hello” it says I/O error. That’s why I was curious why when I verify the disks they all seem to tell me there’s something wrong with track zero, which is probably why it’s not formatting. The disks are good and will formst in other drives, just this drive doesn’t like formatting them.
Just an update on this subject. It appears there’s a problem with the head. Testing the 4 wires the black has continuity with the white but the green has no continuity with the red. Nor anything else like a properly working drive does.
Yup, there it is...
This is the second time now in 40 years that I've heard of a failed read/write head.
Maybe you could cannibalize an otherwise dead or damaged parts drive from a Commodore 1541?
The head from an Alps drive frame from a 1541 should work as far as I know. However, 1541s aren't really much cheaper than Disk ][ or Unidisk 5.25 on eBay so it may be easier to just get another drive and save this one for other parts.
Did you double check whether indeed the head is dead - or could just the cable be broken? The rear part of the cable bends with every movement of the head carriage. It's a thin and flexible wire, usually very reliable - but not impossible that stress may cause it to break over time. If there was no continuity, I'd cut the affected wire to the right of the bracket (see photo), where it is fixed to the carriage assembly, and check for continuity there.
DiskII_HeadCable.jpg
I checked for continuity on all 4 wires from the connector down to the solder points on the head itself and all 4 wires show good continuity. I had a spare head I tried. I know the alignment is out on it but I got it real close with feeler guages so it gives me a steady -8 when I check the speed and it formats and writes to blanks. I know the alignment is out because other drives won’t read what it wrote, but I expected that from this other head. I just wanted to confirm the other head was in fact the issue and I’ve proven it was. Now I’ve got to just get this head fine tune aligned.
Head issues aside, the best way to do a field-repair algnment is with APTEST.
It's the only tool that allows repeatable and reliable alignment without the use of an oscilloscope and an unobtanium test diskette.
Yep, APTEST is great software. Alignments are a pain no matter how you slice it. I’ve only aligned one disk ii and it was tough. But I got it to boot disks it didn’t make and other drives read what it wrote. Hopefully I’ll have a similar success.