Mac SE unable to read from floppy drive connectors?

[unxmaal]

I have a Mac SE that seems unable to read from any floppy drive connected to either the external or internal floppy connectors. 

It states the disk is unreadable, and asks to initialize it.

I've tried with an Apple external FD to external, the native built-in FD to both internal ports, and with a Floppy Emu to both internal ports and the external port. 

The board looks very clean and shiny, with no cap leaks or visible corrosion. 

It's running System 7.1.

Any ideas?

 

[Dog Cow]

Your IWM chip is dead?

 

[68krazy]

Could be bad Bourns filters as well

 

[unxmaal]

How would I test for this? I have another board, that's dead in a different way. Can I pull the IWM and swap?

 

[Challenger 1983]

How would I test for this? I have another board, that's dead in a different way. Can I pull the IWM and swap?

I think

Could be bad Bourns filters as well

I think he is talking about the circuitry on the floppy drive board

 

[BadGoldEagle]

Is your SE equipped with a Superdrive (or FDHD)? If not then it cannot read high density disks or images...

How would I test for this? I have another board, that's dead in a different way. Can I pull the IWM and swap?

Yes, but it depends if your other board is also for the same kind of SE. You can't replace an IWM (from an early SE) with a SWIM (from a late SE) unless you swap the ROM chips as well.

 

[unxmaal]

This board definitely has a 344-0043-A IWM, one of the originals. I thought the Floppy EMU supported that? Am I doing something wrong there? I just picked 'macintosh' from the emu menu.

 

[Gorgonops]

I think

I think he is talking about the circuitry on the floppy drive board

The Bourns filter is an EFI suppression device that sits between the IWM and the floppy connector. Apparently it is a known fail point on these machines.

 

[BadGoldEagle]

This board definitely has a 344-0043-A IWM, one of the originals. I thought the Floppy EMU supported that? Am I doing something wrong there? I just picked 'macintosh' from the emu menu.

Oh OK. So as long as your other board has an IWM, you can swap them out. I had a similar issue with one of my SEs a couple of months ago. It was an FDHD but what happened I think was that the chip wasn't seated properly (even though it looked fine from the outside). I removed the supposedly dead chip and replaced it with a known good one. It brought the FDD back to life. I then reinstalled the old, supposedly dead chip and it kept on working...

You should definitely try with another IWM. It sits on a socket (makes it pretty easy to swap them out) while the filters are soldered to the board. But if it still doesn't work, then one (or more) of the bourns filters are bad. I know charles (aka uniserver or macapps.com) stocks replacement filters.

About the Floppy EMU: Yes, it supports 400k, 800k, and 1440k images. But 1440k images don't work on 800k machines for obvious reasons... You could theoretically get a 1440k floppy working if you put the Emu in HD20 mode... I think. As long as you're using 400k and 800k images, I think everything is all right on the F Emu side.

 

[unxmaal]

Update: finally got around to swapping the IWM, and it worked like a charm!

Reads great from the Floppy Emu. (I haven’t tried a real FD yet.)

Thanks!