Apple IIc mouse compatibility: some details, schematics, and a chip swap to fix compatibility

I have 4 Apple M0100 mice, and only one of them is compatible with my Apple IIc. There are plenty of references online to how some are compatible, and some aren't, but nothing definitive about how to identify them, or what is different about them. So I opened my mice up, and the 3 that aren't compatible are all the same internally, and the circuit board identifies them as made my Mitsumi Elec. The 1 that is compatible is made by Alps. Externally the Mitsumi mice have 2 screws, the Alps has 1 screw. Hopefully details of any other variations can be added to this discussion.

[Image: Apple Mouse M0100 Mitsumi.jpeg][Image: Apple Mouse M0100 Alps.jpeg]

Part numbers on the cords are also different, and that probably matters, as the circuit boards have different connectors. The circuit boards have a single IC on them, for the Mitsumi it is a µPC339 quad comparator (AKA LM339), for the Alps it is a 74LS14 hex Schmitt-trigger inverter.

[Image: M0100 Mitumi board top.jpeg][Image: M0100 Mitumi board bottom.jpeg][Image: M0100 Alps board top.jpeg][Image: M0100 Alps board bottom.jpeg]

To try and better understand the compatibility problems, I drew up some schematics of both mice in KiCad.

[Image: Apple Mouse M0100 Mitsumi.png][Image: Apple Mouse M0100 Alps.png]

The big difference is the µPC339 is an open collector output, and is using 3.3K pull-up resistors, compared to the push-pull output of the 74LS14. It is already pretty well known that the compatibility can be fixed with a push-pull buffer, and there are adapters that do that available. If you aren't handy with a soldering iron, or don't like the idea of modifying your vintage Apple mouse, you might want to stop reading now and go get one of those.

I did try swapping the 3.3K pull-up resistors for 1K, but that still didn't work. I was checking the voltage with my oscilloscope, and even with 1K pull-up it was barely budging the inputs on the Apple Iic that are also connected to the NE556. It might seem problematic that substantial pull-up current is needed, but I suspect it just needs to get the NE556 trigger past a threshold or something, rather than constantly needing 10-20mA or the likes.

So I did a search on Mouser, for quad comparators in PDIP-14 package with push-pull outputs. There is the TLC3704IN, which is pin compatible with the µPC339, very similar specifications, but with a push-pull output that can source or sink 20mA. Currently $2.39 each at Mouser TLC3704IN. I swapped out the µPC339 for one of these, removed the 3.3K pull-up resistors, and it worked! I've now modified all 3 of my Mitsumi mice, and have tested them with my Apple IIc, Apple IIe with mouse card, and Mac Plus.

Here is a picture of the bottom of the Mitsumi board with the pull-up resistors removed. It isn't entirely necessary to remove these resistors, but they are redundant with this modification and will be wasting a few mA of current.

[Image: M0100 Mitumi resistors removed.jpg]

That's incredible! Good write up. Thank you for sharing this.

Also just stumbled across this archived document from Apple in the references on Wikipedia Mouse Compatibility: Macintosh Plus and Apple II Computers. It refers to two vendors, one "Made in the US" that works on both, and the other "Made in Japan". That matches with the labels on the Alps and Mitsumi.

I got my hands on an older Apple M0100 that has two screws on the bottom, like the Mitsumi, but has "Made in U.S.A." on the label. It also has an older style plug. This seems to work fine with the Apple IIc. The circuit board says Apple, and it has 3 pin optical sensors that must have a push-pull output, so no buffer IC or pull up resistors are needed.
[Image: M0100 Apple.jpg][Image: M0100 Apple 820-0070-B board top.jpg][Image: M0100 Apple 820-0070-B board.jpg]

Another interesting M0100 mouse I found has the same circuitry and board layout as the Alps, but has silk screen with component markings and Apple Computer Inc.
[Image: M0100 Apple Alps board.jpg]

I also got an Apple Mouse IIe, model A2M2070, and other than the label, it seems to be identical to the Alps.
[Image: A2M2070.jpg]

>> Glenn Anderson said:

Another interesting M0100 mouse I found has the same circuitry and board layout as the Alps, but has silk screen with component markings and Apple Computer Inc. View attachment 18588 Click to expand...

Do you know if this mouse works with an Apple iic? I have one just like this, but it doesn't work on my early model Apple iic (no memory expansion pins). I have no other Hardware to test this mouse on, so I can't be sure if the mouse doesn't work or if it simply doesn't work with the iic.

>> Billgonzo said:

I just did a quick test with my early model Apple Iic (A2S4000, no memory expansion), and it works just fine. The Alps style mice all seem to be pretty much identical electrically, including the one with the silk screen with Apple Computer markings.

>> Glenn Anderson said:

Thanks, that's good to know. I have been waiting for my Floppy Emu to test software with the mouse, so I have only been able to attempt to test it in BASIC. Maybe I'm doing something wrong with my code, or maybe the mouse just doesn't work for some reason. I guess I'll have to wait until I can fully test it to find out.

>> Billgonzo said:

This is the BASIC code I'm using to test mice.

[Image: MOUSE.BAS.jpeg]

>> Glenn Anderson said:

This is the BASIC code I'm using to test mice. View attachment 21223 Click to expand...

Thanks. I used the same program and could never get the mouse to work. I did find some info on how to use the mouse as a joystick input so that pdl(0) and pdl(1) read the mouse position. I have a ROM 4x so my mouse is slot 7. So what you do is type "pr#7" , press "control+A+return", then type "pr#0", hit return, and then run your basic program that uses PDL. This worked for me, and I found that the mouse wire had a short, and I had to keep the cord bent to get a connection. This might be why the other method wasn't working for me.