TLDR, after repairing and reinstalling AP68 stepper motor in Apple IIC, disks from other IIC's won't read. Not sure how to re-calibrate track 0.
Hi folks, inherited a very clean A2S4100 Apple IIC but it wouldn't read disks. The head would not move. After much troubleshooting and tracing, did a continuity check into the four phases of the stepper motor. One phase did not give continuity. Removed the stepper motor, dissassembled it, and found a bad connection on the "orange" wire where they had soldered it to the varnished winding wire under a heatshrink. That manual soldered connection failed. Replaced the connection, re-installed the stepper motor and voila! The carriage is now returning to the track zero mechanical stopping point.
HOWEVER... the sad news. When the stepper motor was broke, I could kind of finger it along and get my fleet of disks to read the first track or two and give me the loading screen of some of my disk before getting Error 40. Now, no disks will read at all. I did bootstrap with ADTPro and create a new disk successfully.. and that disk can boot. So, we have that situation where the computer and drive are fully functional, but it can't read disks from other computers. I'm not sure how to recalirate - everyone says to go read speedy's guide - but it's for Apple II and not IIC. There's a few things that look weird and different and I get lost in the shuffle. I find a different guide elsewhere that talks about measuring oscilloscope signals - that sounds more like up my alley.
Does anyone have information on Apple IIC disk drive calibration that might help out a guy that has his AP68 stepper motor fail, so the guy had no choice but to yank it and repair it, but now he's up the creek without a paddle because a calibration is needed? By the way, let me know if you want to see photos of an AP68 stepper torn apart, I took lots of photos.
[Update, yes I'm at 299 RPM's verified by 60Hz strobe light, incandescent in N. America, and MECC computer inspector (created by bootstrapping with ADTPro). Remember that I pulled the entire stepper motor so we can skip the basics like drive speed and head cleaning, it can read/write a-ok but can't be compatible with disks from other drives.]
Looks like I've got a shot at doing this with APTEST (if I can find the disk), without retyping the whole thing, there's a good thread going here on how to deal with alignment issues: https://forums.atariage.com/topic/327327-calibration-and-alignment-of-duodisk/
Will update as I go. If anyone has APTEST or a link to buy, let me know, much obliged!
Found and A2R version of APTEST but I don't have a Macintosh in order to try to convert the A2R to .DSK so I can write a disk to my Apple IIC. https://archive.org/download/Antoine_Applesauce_Vignau/APTest%20-%20131%20%28Apple%20Pugetsound%20Program%20Library%20Exchange%29/
Ok, on the atari age forums they found a great way to get into the "approximate ballpark" of track zero. Here's the steps, thanks to those guys:
10 ONERR GOTO 20
20 PRINT CHR$(4)"CATALOG,Sx,Dy": REM "x" is the slot and "y" is the drive number of the questionable drive
30 GOTO 20
Then type RUN
Ok, initially you're going to just see a list of files on your DOS disk. At this time go ahead and remove your DOS disk and hit Enter, and your disk will start cranking and grinding away trying to find a disk catalog. Put in a KNOWN GOOD DISK from a computer with a properly aligned drive (sorry if you don't have any, you'll have to buy one, rent one, borrow one, etc. or maybe some of the guys here can mail you one)
We assume you already physically positioned your floppy disk safely in a way where you can adjust the two screws holding the AP68 stepper motor. I had barely enough room to leave my apple IIC case open and was able to "flip" the drive over and lay it down on the table so it wouldn't short circuit on anything inside my computer case. Note that you don't have to remove the two stepper motor securing screws, just loosen them until you can start turning/rotating that AP68 stepper motor.
Now it's a pure guessing game. Keep slowly turning and moving your stepper motor until your DOS BASIC program can catalog your known good disk. Once you're happy, secure those screws. Voila, you're in the ballpark and ready to do some fine tuning using the APTEST disk. (I'm still searching for a working copy so I'll update this post once I find one and do more fine tuning).
Ok, APTEST is officially here: https://mirrors.apple2.org.za/ground.icaen.uiowa.edu/Collections/Buggie/
However, if you're like me, you're probably used to using .dsk images. This thing is a .sdk image which I don't even know what that is. I installed CiderPress from here to convert it from a .dsk to a .do which ADTPRO can handle. https://a2ciderpress.com/
Now for the really frustrating part. Despite this computer passing all other ROM tests, booting disks, playing disks, and pretty much working great, I still want to do the fine tune calibration with APTEST, but the APTEST image is bugged. When I go to enter the drive calibration feature, it just says "ROM TEST BAD" and reboots the machine.
So... back on to the hunt for working APTEST... I've tried several from the internet wayback machine but they all just say "ROM TEST BAD" when trying to run the drive calibration functions. And I've tried this software with two different working ROM's and same error. So not sure what's up. The ROM ain't bad :-)
Allright a little trickery required to use APTEST on Apple IIC. When you boot the APTEST disk and you see the ], immediately hit CTRL-RESET to drop to the command line. Then type:
CATALOG
And you should see a list of stuff. Then type
BRUN ALIGNMENTTEST
Run the test and make adjustments as necessary, be sure to use known good disks or even better yet factory disks. Don't use disks that you created with the same drive that you are calibrating/diagnosing.
Maybe the APTEST disk is good, but just doesn't know your ROM version, hence the test fails. Maybe your ROM is too new and unknown to APTEST (or vice versa, maybe APTEST required newer ROMs). Which ROM version of the IIc do you have?
See here:
All right, I'm going to deem this drive repaired and calibrated. I've run the APTEST's drive alignment tests and for the most part they're inconclusive. They do give really bad results if your drive is completely out of alignment. I ran the APTEST drive alignment on a known good untampered drive and it gave results all over the board, within the same range as the drive I've been trying to calibrate.
The most useful thing to me was the BASIC program that looped through pulling the catalog. That really helped me get the drive close enough. Last note. I tried very hard to get the set screw for the stepper motor's hub back in the same exact place as before. Not sure how big of an effect mistapping that set screw would have if you ever find yourself in the same boat of having to pull out your stepper motor and then put it back in later. You could do yourself a favor and mark everything carefully with a fine marking pen before you remove any screws so you can try to put it back together exactly how it came apart.
I solved by dumping myself to the DOS prompt before going into APTEST's menu and just running "BRUN ALIGNMENTTEST" and voila I was in. I may never solve the mystery of AP TEST being angry about ROM version. I pulled the factory rom before checking; I put in a ROM 4X that identifies as a "4" with the PEEK command. You can't actually access the alignment test from APTEST's boot menu anyway. At least I couldn't find it as an option.