My system is an Apple IIe ][ with a DuoDisk controlled by a 655-0101 IO card. After years of reliable operation a problem has developed.
I get false "remove write protect tab" messages when trying to read Visifile or Appleworks data discs even though these discs are notched with no tabs. These data discs cannot be read. The message also appears when trying to initialize blank discs with DOS or ProDos masters, again notched with no tabs. Discs cannot be initialized. These problems exist on both drives.
However, both drives will catalog data discs. The names of files on the data discs can be read but the data in the files cannot be read. But programs that require no disc writing are not a problem for either drive. This is includes games. They operate flawlessly.
I have removed the IO card and cleaned the contacts. I also pulled, cleaned and reseated all of the chips on the DuoDisk analog board. Also, both ends of the connecting cable appear to be normal after examination for corrosion, missing pins etc. Unfortunately I do not have a second known good IO card or a second known good cable to help isolate the problem to the IO card or cable or DuoDisk analog board.
Any suggestions to remedy the problem will be appreciated.
Micro (invisible to the human eye) corrosion develops on connectors, female and male. Use contact cleaner on ALL the connectors. Anhydrous Isopropyl alcohol is the standard, but I prefer DeOxit, as that keeps things working longer. You can also scrub with the cleaner and a clean old tooth brush.
Never considered that corrosion may not be visible. I will give your suggestion a try.