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Floppy Drives

Revision as of 16:18, 13 June 2011 by Tdiaz (talk | contribs) (Drive Head Cleaning)
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Apple ][ Floppy Drive Reference

A2 5.25 Drives (20 Pin) 20 Pin - Internal Connected Drives
A2 5.25 Drives (19 Pin) 19 Pin - External Connected Drives
A2 3.5 Drives Apple II Specific 3.5" Drives
3.5 Drive Compatibility Chart
A2 Floppy Controllers Internal Cards

Daisy Chain explained

The term daisy chain is where each device in a system plugs into the previous device, thus eliminating the need for additional interfaces. Each device contains a connector to plug the next one in. On the back of the Apple UniDisk 5.25", AppleDisk 5.25", Apple UniDisk 3.5" and the AppleDisk 3.5" is a DB-19 Connector identical to the one that the drive is plugged into. In a drive chain on an Apple II Computer, ANY 3.5" device(s) must always come before any 5.25" device(s)

Other things that use daisy chaining on the Apple are SCSI hard disks and AppleTalk (LocalTalk) networking and Ethernet networking. Although Ethernet and AppleTalk to don't quite 'look' the same, it's still a daisy chain system.

35 vs. 40 or more tracks

The default capacity on Apple 5.25" DSDD floppy storage is 35 tracks, 16 sectors per track. Some drives, including most of what Apple offers are actually capable of 48 tracks per inch. There are mods for DOS 3.3 to make it format up to 40 tracks, but keep in mind, these disks may not work in another drive. If there is a problem it is usually within the last 5 tracks, the additional ones, that can't be read as they are beyond the normal range. However this is usually only the earliest 5.25" drives as the industry standard was 48 tracks per inch. For clarification, the track layout on all drives is identical, the 'extras' are added to the end, the spacing, layout, beginning on the disk, etc- does not change.

13 vs. 16 Sectors per Track

When the Apple Disk ][ was first offered it was 13 sectors per track. Shortly after introduction this was increased to 16 sectors. Apple used to provide little round stickers that had an Apple logo silhouette in red with a '16' on white type. What Apple should have actually done was provided the same sticker with a '13' for those few disks you would have left over, not for all the new ones you were going to format.

DOS 3.3 Maximum Capacity

The largest volume size Apple DOS 3.3 can handle without any modification what so ever is 400K. The VTOC (Volume Table of Contents) directly supports up to 400K of tracks/sectors in a 32 sector per track maximum. This is what the Sider uses for a "Super Volume" and several of the popular DOS 3.3 on a 3.5" disk methods do.

720K ProDOS Volumes

If you have an DSDD (Double Density) 3.5" MFM drive via a PC Transporter, Blue Disk or Urphi controller, you can format 720K disks as ProDOS volumes. These disks CAN NOT be read in ANYTHING that is 800K only with exception of an AppleDisk 3.5" hooked up to a PC Transporter. If it's an Apple or compatible 800K drive hooked to ANYTHING other than a PC transporter you CAN NOT READ THESE 720K DISKS. They are MFM. These drives can NOT do MFM with exception of the PC Transporter is doing something specific since it has a hybrid version of the IWM integrated with it.

Blank Media 5.25" / 3.5" Disks

Common Media use by disk size/capacity

Disk Size / Type Capacity Compatible With:
5.25" DSDD 140K Disk ][, DuoDisk, Disk //c, UniDisk 5.25"
AppleDisk 5.25" & Other 5.25" Drives
3.5" SSDD 400K Apple External 400K Drive on UDC / Laser 128
3.5" DSDD 800K AppleDisk 3.5", UniDisk 3.5", AE 3.5" Drive
AMR & Laser 3.5" Drive
3.5" DSHD 1.44MB Apple FDHDSuperDrive, AE 3.5" HD Drive
3.5" DSHD 1.6MB Applied Engineering HD+

Common Media use by Computer

Computer Common Disk Type Alternate / Note
Apple ][+ 5.25" DSDD 3.5" DSDD
Apple //e 5.25" DSDD 3.5" DSDD, DSHD
Apple //c 5.25" DSDD 3.5" DSDD
Apple IIc Plus 3.5" DSDD 5.25" DSDD
Apple IIgs 3.5" DSDD 5.25" DSDD, 3.5" DSHD

Substituting DSHD (1.2MB or 1.44MB) for DSDD (360K or 720K/800K) media. DON'T!

DSHD (High Density) Disks SHOULD NOT BE SUBSTITUTED for DSDD (Double Density) Disks. In simple terms, the density (amount of) magnetic particles on the disk per inch is different for the two disks. That means that the disks are not 'optimized' for other than the format they were designed. While they may work, you WILL loose data, and most likely, WILL loose data over time. The proper disks can be found. You may have to mail order them, but they can be found. Again, you WILL loose data. Thats a promise. It's not a matter of it, but only when.

Other Media Formats

QIC-80 34 pin tape backups are supported by the BlueDisk controller.

There were 8" controller cards made by several companies, 2 of the being Lobo Drives, and Sorrento Valley Associates. Storage on 8" disks in Apple format can be as much as 3 MB.

The AmDisk drive uses 3 (Three Inch) format floppy disks. These disks don't seem to be available anyplace.

Rana, MicroSci and Kodak each made a type of High Density disk drive for use with any slotted Apple II. These drives use industry standard "AT" disks, or 5.25" DSHD disks for capacities up to 1.2 MB per disk.

The MicroSci A80 and Rana Elite 3 drives require High Density disks.

Additional IWM/technical information: http://www.stockly.com/forums/showthread.php?t=9

Drive Head Cleaning & Alignment

Clean drive heads make a huge difference in drive performance. 95% of problem drives can be fixed with cleaning the read/write head(s). Yes, 95%.

Before you whip out that cleaning disk and the alcohol, consider this. There is a pretty good chance that the heads on that drive you have right there have never been cleaned and as much, that the drive is probably at least 20 years old by now. If a cleaning disk has not been used regularly it's not going to do much good. It may not even make a dent in the issue.

The next sections you will find information of a general nature on cleaning the heads in various types of common drives. 5.25 in. drives will stand up to much more abuse and handling. 3.5 in. drive on the other hand are considerably more fragile.

The methods covered here may seem extreme, but the end result is a squeaky clean drive head. Some purists may cringe at what they are about to read. From my personal experience, I've never killed a drive. Thats about as simple as I can put it.

Disk ][ / 5.25 Full Height Drives


Cleaning the drive head on the Disk ][ and similar drives is actually very easy. The head assembly is very easy to reach, only "6 screws deep", and one connector. The image above is that of a Disk ][ drive with the cover removed. To remove the cover, remove the four screws on the bottom and slide the cover off the drive.

The PCB (Printed Circuit Board) you see on top is called the Analog Card. The Motor control PCB is the smaller one to the rear of the drive assembly. The next thing you need to do is remove the analog card. Start by removing the drive head connection cable. It is the white connector that is toward the front of the Analog Card. To remove the connector, use two fingers and wiggle it toward the front of the drive. It will slide back about 3/8ths of an inch.

Remove the two screws holding the Analog Card in place. One is just next to the connector you just removed and the other is at the other front corner. Slide the Analog card forward to get it out of the notches and then flip it backwards over the rear of the drive and out of the way.

You should now see the drive door/centering hub assembly. There may be a metal 'lid' over the head assembly. This just snaps down on the sides. Pop it off by lifting one side, then the other.

The drive head assembly will have a pressure pad on a hinged spring loaded lever that is lifted out of the way when the drive door is opened, and when the drive door is closed it is lowered onto the disk and this keeps positive pressure on the moving media so that it maintains constant contact with the head. The label is actually on the opposite side of the disk than the data. In the case of a double sided drive, instead of the pressure pad you would find another head that would by default also act as the pressure pad.

The exception to this would be the Apple FileWare ('Twiggy') drive that was offered in the Lisa computer at time of introduction. It's heads were horizontally opposed and thus each has it's own pressure pad. This allowed the FileWare drive to simultaneously read/write on both sides of the disk for increased performance. An image of the Twiggy Drive / Diskette is shown below.


Just lift the pressure pad and you will see the drive head.

The head should be shiny like glass, white with a small black dot or slash in the middle.

What you will probably find is a black or brown blob which represents years of use built up on the head. If it's brown then it's disk particles from deteriorating disks. This is especially hard for the cleaning disk to ever get off. You could let that spin for days and it would never do a thing to it.

The disk head is made of glass and is very dense. When someone asks me how to clean a drive head, I generally say "spit shine it" and I'm not kidding. I open up the drive and get down to the head, lick a finger and rub on the head, take a shirt tail and wipe it off. Done. Don't be afraid, there's nothing you can do to that head with your finger thats going to harm it. Sometimes that buildup on there can be pretty stubborn and you can be convinced it really belongs there. It does not. That surface should be mostly white and any black you see should be absolutely centered and below the surface.

Again, this is why the cleaning disk will never work and in some ways it's worse, if the cleaning disk is setup for a double sided drive and you place it in a single sided drive- it can tear up the pressure pad and then the drive will have a harder time working.

The head is very durable. The surface of a disk may look smooth, but it's actually super fine magnetic particles. In effect, it's sand paper. The disk head has to put up with this constant friction so it can't be made out of anything that is going to wear down. The disk itself is the weak link in this equation.

You can use Bounty and alcohol, Q-tips and alcohol, etc, too. It needs to be clean and shiny. If it's really bad it will harm disks.

When thats all clean- put the analog card back, plug in the head connector and test it out.

Other 5.25 in. drives

Other drives that use a full height assembly are usually very similar in make up. Half height drives made up around the Alps assembly like the Apple //c internal / External drive, the Unidisk/Duodisk 5.25 and AppleDisk 5.25 are very similar as well and the same instructions without the image generally work. On some of these the pressure pad may not lift much farther off the head meaning you can't see straight down at it, in this case- Q-Tips and alcohol are generally the way to go.

5.25 in. Drive Alignment

In my personal experience, it's a rare circumstance that leads to a Disk II drive, or similar full-height drive actually needing any alignment. Dirty drive heads tend to be the problem. But if alignment is an issue, it's usually because someone else messed with it already.

How do you know if your drive needs alignment? You cleaned the heads the spit shine way and the drive still does not read any other disk you have, or most of them, .. but you can format disks with it, and it's go no problems with stuff written to it. Likewise things written on this one, will not work on others. Once you have figured out with the best process of elimination you have, which drive is actually mis-aligned, you can align the drive that needs correction.

With that, the odds of you having all the "special" tools to align a disk drive are probably slim and none. Have no fear, though. You can do it with .. another disk drive! What you say? Yes. you can do it with another disk drive. Or just a known working disk.

Create a bootable DOS 3.3 disk, and then put some entries in the CATALOG.

Boot a DOS 3.3 System Master and when you get to the ']' prompt, remove the disk and insert one to be initialized.

Type in:


When it's finished, you will see the blinking cursor again. Type in this small BASIC program:




Save it a few more times, too. So that there are some entries on the disk. Preferably, about 20 entries. So


, then SAVE B, .. C, THIS, THAT, THE OTHER THING, etc. About 20 entries and you know you are using more than one sector worth of data. Ideally you do not want the HELLO program to be the alignment aid as you want to just boot first. Thats why we did NOT type in the program first.

Now that you have the disk you need, if you have not already done so, you'll need to remove the case from the disk drive. As described above, and in addition once you have removed the top cover, there will be four more screws holding the bottom cover in place. The ribbon cable is also connected to the bottom cover, unsnap that clip so that the bottom cover can be completely removed from the work area. After the drive case is disassembled place the disk drive on it's side so that you can see the bottom. You will see a large round motor, this is called the Stepper Motor. It's called this because unlike a traditional motor, this one only goes in steps when voltage is applied. Instead of like the Drive Motor that spins consistently, a Stepper Motor takes a step of a specific amount. Depending on the capability of the disk drive, this may vary, but the Disk II and compatible hardware are between 80 and 160 steps per inch. If the disk drive can not do quarter tracks, it's 80 steps per inch. Some odd clone drives won't do this, which means they will not work with some copy protected disks.

There are two 'ears' on the stepper motor that are usually secured with some form of thread lock. Nail polish is an acceptable household replacement for this when you are done. Loosen the two screws you see just slightly, enough to break the grip so that you can rotate the motor in place. You do not need to move this very much at all. Attach your drive to the #2 position on the controller card and boot your floppy in drive one. When you get to the basic prompt, type


and then remove the disk and place it into the drive to be aligned. Type


If the drive shows a directory then your alignment is probably really close anyway. Or if it didn't work earlier and now it does, just loosening the screws might have moved the motor just enough. As I said, you don't have to move this very much. Type ]RUN ALIGN and the drive should start spinning.

The program you are running is simply a looping disk catalog command. As you move the motor from side to side you will hear the drive recalibrating. (Making that 'grinding' sound), when the alignment is proper you should see the catalog data. You want to move the motor from side to side ever so slowly that you find the limits of each direction and then you can center the motor between these two points.

To aid this, we're going to make some marks on the drive itself, so center the motor on the bottom of the drive with the screw heads, and make a scratch with an X-Acto blade or similar. That is your center line. Do it just on the motor ear portion at first. Then when you rotate the motor to one end, just when the catalog reading starts to get to where it's hesitating, not coming in as fast, and eventually you should hear nothing but recalibrating, come back in just a little to where it first reads the catalog again and now make a mark opposite the center of the motor ear, on the disk drive chassis itself.

Now do the same thing in the other direction and make the second mark. These are your extreme points. If you put that marker on the motor in the middle of these two points you drive is now aligned well enough and in the real world, will work just fine. The term, 'Good Enough for Government Work' comes to mind. I probably wouldn't run a nuclear power plant, or warp drive system on this type of setup... well, then again, maybe *I* would. ;) But you get my point. If you have no other tools, you can still do this.

When you have it centered, and you are happy with it, tighten the screws and see that it still works. Now you can hit CTRL-RESET and at the prompt, swap the disk in the drive with some other DOS 3.3 disks and catalog them, you should see a catalog track right away.

The next test is to swap the drive to the #1 position and boot that alignment aid disk you created. Shut off the computer, swap the cables, and turn it on. The disk should boot to the prompt. As a final test, boot a ProDOS disk now, as ProDOS is a bit more particular. If thats all good, you're done. Put some nail polish on the screws and re-assemble everything. Clean the drive head one more time since you are inside, though. It can't hurt. :)

This process works on pretty much any 5.25 inch disk drive, full or half height. Though the motor arrangement and movement may be totally different. In some cases there is an eye that sets where track zero is, and then the drive counts from there. The theory is the same, but it's a little more time consuming as you have to wait for each recalibration for the results. But you would move the eye point. Others use a metal ribbon wrapped around a spindle and have anchor points. By moving the anchor points, changes the alignment. However I will say that drives that tend to use these alternate methods are usually way more resilient and generally don't have this issue. Particularly with Half Height Drives. But exploring mechanical things is fun, too. So.. have at it!

Adjusting Drive Speed

With the drive disassembled as specified above, if it's a Disk II or similar drive, there is usually a smaller PCB (Printed Circuit Board) located on the rear of the drive assembly. There will be a potentiometer on there that usually controls the speed. With the drive on it's side, you should see a wheel with a black and white patterns on it, similar to a turn table (record player). With the aid of a fluorescent light in the vicinity, you can set the speed to the default using just the light and the spinning drive. You may also use and older version of Copy II Plus . You generally are aiming for 300 RPM, if there is a counter. Or the "center" of whatever the software says the range is. If you are using the fluorescent light, just turn on the computer with the drive hooked up and no disk inserted. Turn the pot until the spot you have focused on, is stable. Not drifting. It will become evident to you when you see it the motor actually spinning. There are usually two bands. Sometimes labeled 50 and 60. In the US, you'll use the one labeled 60, or 60Hz. In part of Japan you might use the 50Hz, where as the rest of Japan you would use the 60Hz. .. and most of Europe, you'd use the 50Hz. Generally, if your TV standard is PAL, it's 50Hz, if it's NTSC it's 60Hz.

If you are using software as the aid, just center it. In the circumstance where you can use software and the light method, the light method over-rules and will usually dis-agree with the software method. Thats the way it is.

Other disk drives, particularly Half Height ones have the speed setting screw in other locations, and some of them are even labeled and accessible from the exterior. You just have to look around for it first.

3.5 in. Drives

Cleaning 3.5 in. drive heads can usually be accomplished with the cleaning disk with far far more success than the 5.25 in. drives.

But in those cases where it's not working, the concept is similar but you may need to take apart less or far more to get to the heads themselves.

But .... read on:

3.5 in. drives are generally FAR MORE fragile than 5.25 in. drives.

I'll say it again. 3.5 in. drives can be far more susceptible to damage by handling.

3.5 in. drive also don't generally get as bad as 5.25 in. drives because the disks are shuttered. But should you need to clean heads..


I can tell you for a fact that most double sided 3.5 in. drives will not work again if you simply reach down and lift up that drive head. They are made of tensioned brass or copper sheeting and not a spring that just snaps back. They will actually bend and not go back when you let go. The image above is of one side of a typical 3.5 in. drive head.

Now I have been able to re-tension most of these when thats all that has happened, but the same way those are made, the heads themselves are actually floating on tensioned thin metal. That means if you push down on them extensively, they will most likely come out of alignment. Disk drives are all about alignment - that way they are all .. "on the same track".

As you can gather from the image above, some due diligence is in order when handling 3.5 in. drive heads. Alcohol and Q-tips are generally the best to use and with one hand only.

Do not re-use the Q-tip, dip it once, put it in, twirl it around a few times, take it out and look at it. Turn it around and do it again. Do not re-use them because it will start to have threads hanging off and those can get caught on the head and when you pull it out, by the time you feel the tension and stop- it's probably too late. You've already pulled the head.

3.5 Drive Alignment and Speed Settings

Because of the nature of 3.5 drive assemblies, and the advanced state of construction alignment is generally not an issue. If alignment is a problem it's most likely not a correctable issue without additional parts. The Sony auto insert drive assembly has an optical method of head alignment and works using the "from track zero" method. The drive heat itself, (pictured above) has a tab hanging off it at the rear of the lower half the head assembly, (Similar to that tab in the above picture, but it would be at the rear, and on the lower one only) and the eye assembly is movable. This sets the reference point. Due to the way that 3.5 inch drives work it's not as easy to set this using the above methods for the 5.25 inch drives, but it's not impossible either. It's just a lot more unlikely that it needs to be messed with at all.

Speed settings is a non-issue with Apple compatible 3.5 inch drives as the motor speed is controlled by the drive itself and varies according to track position. 3.5 inch drives tend to be variable speed. There isn't much you can do here.

Security by Obscurity

So, you want to store some data on some disks that you want a fairly good chance that no one else can read? Understanding the above procedures on the 5.25 inch drive, set the drive head alignment to some extreme end of travel and when you format any disk in that drive it will not be readable anywhere else. Just make sure you mark all the disks accordingly to indicate that they are of some type of 'special' format. Likewise, with a double sided drive, swap the head positions so that they are reversed. Of course, all data will need to be written to these drives as read from a normal one. But... you see the possibilities here. :)

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