I have an Apple //e with a DuoDisk Card and Drive Unit. I haven't used it in many years, preferring modern solid state; however, I wanted to get the drive going again. I tested it as-is and found speed issues. I performed maintenace to clean the heads, correct the speed, clean up, etc. Drives are operating as they should (speed check, etc.).
However, I purchased a box of new DS/DD disks to use with the setup. I tried to format every one of the disks in both drives, and spun up, moved the head to track 0 and tried to format, but failed immediately with "Track $00 Error". I tried formatting as ProDos and AppleDOS. Since both drives are doing this, I assume it is the duodisk controller board in the drive.
I pulled the board from the drive, removed the capacitors and tested them. One was out of spec, but I replaced them all. I tested the IC's that I could (all of the 74' logic chips), and found the 7407 was not working. So, I replaced the 7407. Tried it all out again, but still get the "Track $00 Errors" .
Any suggestions? Is there a common failure I should inspect on the drive controller card? Should I look instead at the DuoDisk card in the computer?
You said, "Drives are operating as they should." Please confirm that you can read and write existing disks. What did you use to set the speed?
Thank you for the reply. Unfortunately, I do not have any disks, other than the blanks. As such, I can't test reading/writing. I can't format to begin with.
When setting the speed on each disk separately, I used a 60Hz flourescent with the timing sticker on the motor to make the macro adjustment. I then used (IIRC, Copy Disk ][) to run a speed test with a floppy in the drive to do the fine adjustment to get as close to 300rpm as possible.
If you were able to set the speed with a program (Copy II Plus?) then the drive probably can read and write disks. Maybe try a different program to format the disks?
If you have the Apple 5.25 floppy controller in slot 6 and a blank floppy in drive 1 of the DuoDisk, and you boot up from a solid state media in another slot using a disk image like the Apple DOS 3.3 System Master, can you do this:
NEW
10 PRINT "HELLO"
INIT HELLO,S6,D1
?
Thank you for the suggestion. I dug out my Disk II card and floppy emu and booted from DOS 3.3 since I normally just boot from a ProDOS smartport hard drive image.
I ran it and the disk started spinning with light on, slammed the drive head a few times to get to the beginning, spun some more, then beeped with:
I/O ERROR
Thanks. I have tried a few different utilities with format to no avail. Also, the test given by softwarejanitor below.
As you said, the speed test requires a disk and it just spins but the disk is unformatted and blank. I tried "The Disk Repair Kit" by Dave Winzler, which tries to repair a diskette. It begins by reading the catalog (an empty disk in my case), but it just keeps reading and progressing (see screen shot below). So, it seems that the drive talks to the computer, but I just can't format (or presumably write) to a disk.
screenshot.jpg
After an hour, it has scanned about half of the disk, but it tells me that at a minimum the disk is moving to different tracks, etc.
As a curiosity, what kind of disks are you using? You want single or doube density media at most, the high density floppies used in later PC clones usually won't work. Getting good disks these days can be an issue as a lot of media has gone bad over time. It has been quite a while since most 5.25" floppies were made.
Also just for grins, try putting the blank disk into drive 2 and change the test to
INIT HELLO,S6,D2
If you haven't already done that, of course.
If it works with drive 2, it might be worth opening up the drive and swapping the drives, as at least you'd have a sort of usable setup that way, albeit you'd still need to deal with the other drive at some point of course.
Thank you.
I am using double density disks, and the same happens with drive 1 or 2. This is why I was stating in my original post on my suspicion of the DuoDisk board itself. While it did have a faulty 7407, I replaced it, but the issue persists. I don't have reason to doubt the duodisk card in the computer as I can use the floppyemu connected to it with two simulated drives without fail.
I am curious about what diagnosable errors there may be for the actual controller board in the duodisk. I am unsure of how to test the non 74-series chips on the board or whether there may be a known fault.
As a followup to working with the Disk Repair Kit software, it always fails in trying to read track $00, but can read the other tracks. If I try to format individual tracks though, it fails for any of the 35 tracks.
Could you post a photo of the disk controller card and the board from the duodisk that you worked on.
Apologies for the holiday delay...
Interface Card
DuoDisk Analog Board
When it comes to issues with reading/writing due to the controller card, more often than not the 74LS174 is the culprit.
One issue reported in the past was a missing -12v.
I have a TIF image of the schematic for the duodisk analog board. I don't know how to share it here but one sleeper is it does require minus 12v supply which I assume wouldn't be needed by a drive emulator.
Looks like -12v comes in pin 23 of the cable ?
Larry G
https://bitsavers.org/pdf/apple/disk/5_inch/050-5014-D_Duodisk_Analog_Bo...
Do you have any electronic test equipment. eg multimeter, oscilloscope?
You could test the input to 74LS125 Pin 1 to see that it goes low during writes.
Thank you for the suggestion. I checked each of the power pins, and all were the appropriate voltages. 23 was -12.2 V.
Thank you, I think you may be on to something. Hooking my oscilloscope to pin 1 of the '125, it is always held high. I tried to format a disk, I tried to save a BASIC program, etc. It would never go low. I'm not sure though if it tries to read something prior to either of those tasks though that prevent it from switching to /W. I had previously tested the stock 74LS125 and it checked fine with my tester. I have some HC125's in my parts bin. I swapped one in, and the behavior was identical: no ability to format. So, the original '125 is confirmed working.
Looking at the schematic you sent, pin 1 of the '125 is connected to R/W on pin 4 of the MC3469; however, it appears that is a different schematic from my duodisk analog board. There is no MC3469 anywhere on my board (see pic above). Tracing pin 1 on the '125, it goes to pin 5 on the 74LS32 and pin 11 on the 7407. I have to say that I don't understand the circuit. Pin 1 of a '125 is an input pin to enable/disable pins 2 and 3. But it is connected to input pins on the '32 and '04. So, I don't know what is driving that pin.
atomicham it appears you have the later revision of DuoDisk analogue board 676-[ ]107.
There doesn't doesn't appear to be any schematics for this card and while the parts around the MC3470 appear to match the schematic I linked to previously, there are noticeable differences with completely different IC's being used.
I would be happy to try and document the schematic from photo's of both sides of the DuoDisk analogue board.
If you want to try and document the board, could you remove the board and disconnect all cables before taking photo's.
Could you also provided the any component identifying markings on Q3 - Q9 and DA1 - DA5.
Thank you. I greatly appreciate your help with this. I am happy to help tracing things with a probe. I will take the board home as it will hopefully allow me to find extra time (though my son gets back from University tomorrow, so it may be hectic).
For DA1-5, the writing on those is very faded and extremely difficult to decipher, but what I can get:
DA1 - DAN201A
DA2 - DAN201A (I can only make out what appears to be the top of an A)
DA3 - I cannot see/make out any writing on it
DA4 - DAN201B
DA5 - DAN201C
Q3, Q4, Q5 - 3906
Q6, Q7 - 3904
Q8, Q9 - 1205
The images are shown as preview, but I uploaded full resolution if you click through and download to your machine.
top.jpeg
bottom.jpeg