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Apple IIGS Floppy Drive Weirdness

Joined
Dec 26, 2009
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Kelowna, BC, Canada
Hi Folks! Hope you can help with a very weird problem...

I picked up a used Apple IIGS. When I tried booting the thing, the drive would click a few times, and then I'd get the "Check startup device!" screen. Not good, but the weird thing is that after that, the disk is unreadable. I try reading it on another machine and I get "I/O Error". I reformat the disk on another machine, copy ProDOS onto it, and try booting it again on the IIGS. Same thing, after booting it's unreadable. I tried booting other disks that boot fine on other machines. Same thing, it doesn't boot and the disk becomes unreadable.

The IIGS is ROM Version 01 with no cards. The drive is an Apple 5.25 Drive (A9M0107). I'm using a Commodore 1702 composite monitor, an Apple Keyboard II (M0487), and an Apple Mouse (A9M0331). In the control panel, everything is set to the defaults.

I have another, working, IIGS and have tried swapping the power supplies, no difference. I tried swapping drives, no difference. I even tried swapping the keyboard and mouse, no difference. I checked the voltages, they are fine. I checked the battery voltage, it's fine. I did a self-test, no problem. I even tried the power supply and drive from the problem IIGS on my other other IIGS, they work fine. The disk boots and is fine afterwards.

At this point, I'm baffled. Obviously the booting problem is an issue with the motherboard but I have no idea what it is. And why is it making the boot disk unreadable? Any help on this would be greatly appreciated!

- Rick
 

SomeGuy

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It sounds sort of like the write request line that outputs to the floppy drive is stuck. Does write protecting the disks make any difference? It would be interesting to see if somehow disconnecting just the write request line would make any difference, but there may be other damage to the floppy port.
 
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I tried write protecting the disk and it made no difference - the disk still became unreadable.

Funny thing, I always assumed it was the floppy drive that dealt with the write protection, rather than it being a signal sent back the the computer. I rewrote the disk on another machine with ADTPro and it complete ignored the write protection. I guess some programs just don't care. :)

I'll check the write request and write data lines on the motherboard - maybe something shorted. Thanks for the tip!

- Rick
 

george

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I tried write protecting the disk and it made no difference - the disk still became unreadable.

Funny thing, I always assumed it was the floppy drive that dealt with the write protection, rather than it being a signal sent back the the computer. I rewrote the disk on another machine with ADTPro and it complete ignored the write protection. I guess some programs just don't care. :)

I'll check the write request and write data lines on the motherboard - maybe something shorted. Thanks for the tip!

- Rick

If a floppy drive writes to a write protected disk then the FDD's protection circuitry is either faulty or intentionally crippled.
 

retrogear

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When you swapped drives, did you swap cables? The write protect line goes thru the cable direct to the IWM chip on the motherboard. If you swapped cables too then sure seems like IWM chip is bad.
Does the media of the disk look scratched? Maybe the bad drive scratched them up first?

Larry G
 
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SomeGuy - I checked the floppy drive connector on the motherboard and didn't see any obvious problems. And seeing as the 3 1/2" drive worked (see below)...
george - I tried using ADTPro, on my Apple IIc, to format and write to a 5 1/4" disk with a write protect tab on it. The program formatted it and wrote to it without complaint. Maybe someone else should try this to confirm?
retrogear - The cables for these drives, the Apple 5.25 Drive (A9M0107), are not detachable. So yes, the cables were swapped. The media is fine - it was brand new out of a box and I tried different disks.

Here's a interesting new wrinkle. I tried attaching a 3 1/2" drive, the Apple 3.5 Drive (A9M0106), and booting GS/OS 6.0 off of a 3 1/2" disk. It booted fine! I then daisy chained a 5 1/4" drive off of it. With nothing in the 5 1/4" drive I booted it up. The 5 1/4" drive was accessed, the drive clicks and the light goes on. It boots fine off of the 3 1/2" disk. But there's no 5 1/4" drive on the desktop! Huh?

Even better, I put a bootable disk in the 5 1/4" drive and booted it up again. The 5 1/4" drive was accessed, the drive clicks and the light goes on, as before. It boots off of the 3 1/2" disk, as before. And there's still no 5 1/4" drive on the desktop. And guess what, when I take out the 5 1/4" disk and try it on another machine, it's unreadable! D'oh!

Maybe this machine just has a vendetta against 5 1/4" drives?

- Rick
 

KC9UDX

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If a floppy drive writes to a write protected disk then the FDD's protection circuitry is either faulty or intentionally crippled.

Are you sure? I thought write protection was handled in software or firmware. I seem to remember being able to write to write-protected disks. But maybe that wasn't on the Apple.
 

retrogear

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Sounds like a bad analog card in your 5 1/4" drive. It could fault and keep current running through the r/w head to do some erasing.
About the cable, I was looking at the back of my //gs drives and thought the cable was screwed on but I see it's just to chain to the next drive.

Larry G
 

SomeGuy

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Ok, so it's just this one 5.25" drive that is exhibiting this behavior. Yea, the electronics in it have to be borked. if it is in good cosmetic condition, it is probably worth hunting down replacement parts.
 
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retrogear and SomeGuy -

It's not just the one 5 1/4" drive. I've attached another 5 1/4" drive to the IIGS and it does exactly the same thing - reads the disk, doesn't boot, and then the disk is unreadable. Both drives work perfectly on both a IIc and another IIGS. I think this has to be a motherboard thing.

- Rick
 

retrogear

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> I think this has to be a motherboard thing.
Well, then we're back to the IWM chip which controls both kinds of drives. Probably not much can be done w/o a new motherboard.
I did read something interesting that whenever a motor on port is accessed on the 5.25 drive that the cpu speed is slowed from 2.8MHz to 1 MHz.
Makes me wonder what it would do to a disk if it failed to reduce speed. Like a 5.25 drive on steroids :)

PS - I suppose you could change in the control panel slot 6 to your card and add a Disk II controller but then you would need the ribbon cable type of drives.

Larry G
 
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I'm thinking I could get an Apple 5.25 Controller and stick it in slot 6. Then I could run the 3 1/2" drives from the internal floppy port and the 5 1/4" drives from the card. Does that sound possible?

Edit: Oops, I see Larry already suggested this. The Apple 5.25 Controller actually uses a 19 pin D connector instead of the ribbon connector so it should work with my 5 1/4" drive.

The Apple 5.25 Controller cards seems to be pretty plentiful and cheap (except for the shipping to Canada - Arg!). It might be worth a try.

-Rick
 

KC9UDX

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Will those work with 3.5" IIc/IIGS/Laser 128 drives? (I can't quite remember)

Yes.

It seems to me there is one drive that won't work with it but it is a rare, unobtainable one. My memory could be way off on that one though.
 

retrogear

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>I'm thinking I could get an Apple 5.25 Controller and stick it in slot 6. Then I could run the 3 1/2" drives from the internal floppy port and the 5 1/4" drives from the card. Does that sound possible?
One thing that concerns me is if the problem IS the IWM chip and the failure progresses, the 3.5 could fail eventually? You might be better off finding a controller for both 3.5 and 5.25 but probably rare.

PS - I have the hardware to test mixing the onboard 3.5 with a 820-5003-A 19 pin controller. Is it a safe idea to try this? I have an A9M0107 drive like yours but this controller is used with my A9M0104 drives
Such a mix of combinations but good information, I suppose. I'm learning just by reading up on all the "stuff" I have ...

Larry G
 

george

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Are you sure? I thought write protection was handled in software or firmware. I seem to remember being able to write to write-protected disks. But maybe that wasn't on the Apple.
Absolutely. What you seem to remember wasn't on Apples, and wasn't on PCs...You are able to write to WP diskettes if the drive is modified to ignore its write protection sensor. WP is indeed handled by software but cannot be overriden by software.
 

HoJoPo

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PS - I have the hardware to test mixing the onboard 3.5 with a 820-5003-A 19 pin controller. Is it a safe idea to try this? I have an A9M0107 drive like yours but this controller is used with my A9M0104 drives
Such a mix of combinations but good information, I suppose. I'm learning just by reading up on all the "stuff" I have ...

Larry G

Shouldn't be a problem to run the Apple II 5.25 controller in slot 6 (set to "Your Card" in the control panel) and use the built-in port on slot 5 for 3.5 drives. My developer seed prototype IIgs (aka IIBF) had a disk ][ controller in slot 6 and disk ][ drives when I received it, they worked with no problems, and a 3.5 drive on the built-in port worked fine at the same time.
 

bear

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FWIW I had this exact same problem with an SE/30 twenty years ago. I replaced the system logic board.
 
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