Apple IIc cannot write to any drive

[kpcnsk]

I dug the old family Apple IIc out of storage and picked up a Floppy Emu. I inspected the board and drive and cleaned it up. Booted fine. Next I upgraded the ROM (including W1/W2 mods) from v255 to v4 so that I could read and boot from the FEMU. Also installed the BMOW Internal/External switcher for the IIc. All seemed well.

I can now boot from the FEMU or the internal IIc drive. The computer can read disks from either drive with no problem. YAY! Unfortunately, writing is another story. It seems as though disk writes from saving files isn't possible. Copying doesn't work, nor does formatting. Instead I get various disk write error, depending on the program used.

I'd appreciate any insight into the issue, including even what to trouble shoot next. I could reverse the ROM upgrade to see if the new ROM is the culprit, or start examining circuitry in either the computer or the disk drive. Thanks for your help.

 

[bibilit]

There is a switch to provide write hability or better disable it if required.

Can help ?

 

[kpcnsk]

There is a switch to provide write hability or better disable it if required.

Can help ?

Thanks, but I don't think it's the write protection switch on the floppy disk drive. The inability to initialize or write to disk even happens with other drives, including the Floppy Emu. I've tried various configurations of the drives, and the problem persists. I did refresh the solder on the floppy drive connectors, but that didn't help.

 

[tony359]

was the drive working before? The writing circuitry on the drive is driven by a write IC. Without that IC - or with a faulty one - the drive will boot fine and read fine, would just refuse to write.

If you have a spare IC, I would swap it. Or at least re-seat it if the IC is socketed.

The IC is CA3146E. There is no adjustment for the writing feature so if the drive works, chances are the IC has gone.

But if you say the issue presents itself with multiple drives, then I'd look at the motherboard. Or the flat cable, they can get dodgy over time and might need to be re-crimped.

 

[kpcnsk]

Yeah, tried refreshing the solder on the CA3146, as well as the other ICs on the drive analogue board (74LS125, MC4370, UNL2003). I don't have spares to swap out, but tried a different floppy cable. Resoldered the internal and external drive connectors, as well as the IWM.

Given that this issue happens with multiple drives, though, I'm suspecting a failed IWM. A bad IC on the analogue board of one drive shouldn't affect the others. It's pretty weird though, since it seems to read without issue.

 

[tony359]

I don’t know how the IWM works but I can tell you that if you remove the write amplifier, the drive boots and reads no problem.
So I suppose that if the writing section of the IWM is broken, you get the same.

If you tried more than one drive then I’m afraid the issue is with the main board.

 

[kpcnsk]

If you tried more than one drive then I’m afraid the issue is with the main board.

Yeah, that's what I've sadly come to suspect.