Replacement IWM chip

[dmu...@gmail.com]

Hello --

I have an Apple IIc that I think has a blown IWM chip. The floppy drive spins constantly while the machine is on. I don't have any floppy disks to try with it, but I wouldn't be surprised to find out read/writes don't work either.

That said, is there is good source to purchase replacement IWM chips anywhere? I did a quick Google search, but nothing jumped out on the first couple of pages of results.

I know some of the early Macs used IWM chips as well. Were these in the same packaging as the ones in the Apple IIc? Can I just pull one out of a broken Mac like a Plus or SE and swap it into a IIc?

Thanks!
dennis

[Michael Black]

On Thu, 18 Sep 2014, dmu...@gmail.com wrote:

> Hello --
>
> I have an Apple IIc that I think has a blown IWM chip. The floppy drive
> spins constantly while the machine is on. I don't have any floppy disks
> to try with it, but I wouldn't be surprised to find out read/writes
> don't work either.
>

Aren't there still buffers between the IC and the drive connector? If so
(and I don't know), you might try replacing those first, they'd be
cheaper.

Make sure the connector is the right way. Again I'm not sure about the
Apple II, but on "regular" floppy drives, one side of pins are at ground,
so if you get things backward, you end up turning on a bunch of things,
including the motor. I mangled a few disks that way.

> That said, is there is good source to purchase replacement IWM chips
> anywhere? I did a quick Google search, but nothing jumped out on the
> first couple of pages of results.
>
> I know some of the early Macs used IWM chips as well. Were these in the
> same packaging as the ones in the Apple IIc? Can I just pull one out of
> a broken Mac like a Plus or SE and swap it into a IIc?
>

What's in the IIC? Memory says the IWM in the Mac Plus is a surface mount
kind of IC, a square package with fine pins to solder to the board on all
sides. I don't know what the IIC is like.

If you look and get the part number in the IIC, I have a Mac Plus board
that I think is easy to get to, and I'd check to see exactly what's on it.

Michael

[David Empson]

Michael Black <et...@ncf.ca> wrote:

> On Thu, 18 Sep 2014, dmu...@gmail.com wrote:
>
> > Hello --
> >
> > I have an Apple IIc that I think has a blown IWM chip. The floppy drive
> > spins constantly while the machine is on. I don't have any floppy disks
> > to try with it, but I wouldn't be surprised to find out read/writes
> > don't work either.
> >
> Aren't there still buffers between the IC and the drive connector? If so
> (and I don't know), you might try replacing those first, they'd be
> cheaper.
>
> Make sure the connector is the right way. Again I'm not sure about the
> Apple II, but on "regular" floppy drives, one side of pins are at ground,
> so if you get things backward, you end up turning on a bunch of things,
> including the motor. I mangled a few disks that way.

Yes, I'd investigate the drive before assuming the IWM was faulty.

> > That said, is there is good source to purchase replacement IWM chips
> > anywhere? I did a quick Google search, but nothing jumped out on the
> > first couple of pages of results.
> >
> > I know some of the early Macs used IWM chips as well. Were these in the
> > same packaging as the ones in the Apple IIc? Can I just pull one out of
> > a broken Mac like a Plus or SE and swap it into a IIc?
> >
> What's in the IIC? Memory says the IWM in the Mac Plus is a surface mount
> kind of IC, a square package with fine pins to solder to the board on all
> sides. I don't know what the IIC is like.

The IIc has a dual-in-line chip, at least in 1984-1985 models I've seen.
I don't have one handy to check the specifics.

The IIgs (late 1986 or 1989) has a surface mount IWM, as do the Mac SE
and II (early 1987) - those two can be upgraded to a SWIM so the IWM is
socketed.

It so happens that I have a naked Mac 128K board here, and it has a
dual-in-line IWM soldered to the board. It should be possible to pinch
one of those and use it in a IIc. The chips are not specific to the Mac
or Apple II: an input tells them whether to operate from a 7 MHz or 8
MHz master clock.

The one on this Mac 128K board is labelled (after removing the dust):
344-0041-A � Apple 1983, with a date code of 8417.

I expect the 512K Mac is the same as the 128K. I don't think I've seen a
Mac Plus motherboard so I'll defer to Michaels recollection in that
case.

--
David Empson
dem...@actrix.gen.nz

[Michael Black]

My memory is wrong, so I must have been picturing what I saw when I looked
at a IIGS or some later Mac.

Yes, on a 512EK board (basically the original Mac with a daughter board
and 512K of RAM) the IWM is clearly marked, and the IC number is
344-0041-A and it's soldered in, but as you say, a 28pin DIP.

On the Mac Plus board, it's also properly marked "IWM" on the
silkscreening, and the IC is marked 344-0041-B. It's also soldered in.

Sorry about that.

Michael