I'm having issues with my IIc drives. It reads from all the drives without issue, but not write to the internal, extrenal, or Floppy Emu in either location. Based on some forum sleuthing and my own investigations, I suspect that the issue is with the IWM. I'd love to have a second opinion on that diagnosis.
The story so far... I rescued my family's old Apple IIc from my mother's basement last month. It hadn't been used in at least 15 years, but was stored in a dry, climate controlled environment. Once I got it, I opened it up to take a look at the internals to make sure there wasn't any obvious damage. Other than being a bit dusty, it looked good, so I tried booting from floppies, and was successful. Played a few games and opened Appleworks successfully. It did not occur to me to try saving a file at the time, but since it seemed to be in order, I ordered a Floppy Emu. I also ordered a ROM upgrade (ROM 4), and installed that without any issues as mine had the original version ROM 255.
Once the FEMU (and BMOW's IIc internal/external switcher) came, I set it up and tben booted with the FEMU without any issues. It worked as expected, so I decided to start by copying files from the old floppies to the FEMU. Immediately I encountered various issues whenever what I did required writing to the drive (formatting, saving files, copying files, etc.). Also tried writing on the internal and external floppies for the first time, but encountered the same issue.
Things I have tried:
- Cleaning the drives.
- Using a different SD card in the FEMU
- Using various drive setups, in isolation and in combination.
- Swapping out the FDD cables
- Resoldering the internal and external drive connections on the motherboard. Continuity tests with a multimeter are fine.
- Resoldering all the ICs on the internal analogue board. Continuity tests with a multimeter are fine.
Things I have not tried:
- Redoing the capacitors on the main board or the drive board.
- Swapping out any ICs, other than the ROM.
- Swapping out other known working drives, as I don't have any
- Doing any tests of the installed ICs
At this point the testing (and solutions) are becoming more expensive, and I'm unsure how to proceed. Because this happens with multiple drives, I suspect an issue with the motherboard, likely the IWM. I'd like to test it to be more conclusive, but am unsure how. I welcome any advice on things I may have overlooked or next steps. Thanks!
Hopefully it isn't the IWM, as that's a nearly ubobtanium chip. The only source for replacements is generally other machines being parted out, which means not many available out there.
It's another chip that it would be great if someone made a replacement for based on a CPLD or FPGA. The other two that I'd love to see being the IOU and MMU chips. There are already FPGA based replacements for the keyboard chip and a few others, so it is probably doable. The IWM may be easier than some others even because Steve over at BMOW did a lot of work duplicating the IWM functionality for the Yellowstone card and he released a lot of it as Open Source.
Unfortunately as far as troubleshooting this the 4 things you note that you haven't tried are really where you need to go. Perhaps there is someone who can help you out. Since you mention a basement I'm assuming you're probably not close to me. I'm in Texas and basically we don't have them down here because most places the ground is too hard to dig and many places where it isn't like a lof of the Houston area the ground water level is too high for basements to be practical.
Anyway, finding someone close by that could help you would be best but you may end up having to do some shipping at least if it involves having stomeone else look at things or borrowing hardware to test with. And of course there would have to be a level of trust on both sides for that kind of thing.
Yeah, I know it wouldn't be an easy fix if it turns out that's the case. I wish I knew how to test to see if it is indeed the culprit.
My mom's house is in Nebraska where basements are standard-issue. I'm actually also in Texas, so just down the street, so to speak. ;)
I also grew up in the north where you couldn't give away a house without a basement due to the (not entirely unreasonable) fears of Tornadoes.
Texas... you could be right down the street or 8 hours away, depending on where. I'm in the Austin area... but it's 4+ hours to DFW from here, 3+ to Houston and 2+ to San Antonio... If you are in the Austin area or near enough to travel here I might be able to help you out. I at least have a few of the things you don't to try.
I'll PM you.
As I said in the PM, I don't have a //c or an extra IWM to try, but what I can do is test your drives in a known working computer and I have known working drives that can be tested on yours. Also I may have some of the other chips to try, although I'm not sure how much in a //c is socketed. I've never actually owned a //c. I started out with a ][+ and I have a bunch of //e units, a IIgs and some clones, including a couple of Laser 128s. For whatever reason I never got a //c. I guess one didn't happen along at the right price or something.