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M0100 no up/down movement


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So I recently acquired an Apple M0100 mouse to go with my recently acquired Macintosh Plus. I can move the mouse from left to right, and I can click, but I cannot move the mouse up or down.

 

I disassembled the mouse and gave it a good cleaning. I also checked the continuity for all of the pins and verified that the cable is good. I also checked all of the traces, and they all seem to be good. The only thing I can think of is that the actual sensors that detect the movement for up/down may be bad? But is seems like quite a coincidence that both up and down would be bad... I don't see anything visibly wrong with them.

 

I'm not entirely fluent in electronics, but the readings I am getting across the resistors and the sensors match what the working left/right ones are giving me.

 

Does anyone see anything on the board that I'm missing?

 

If the mouse is good, then the alternative is that there is something wrong with the computer. Unfortunately, I have neither a spare Plus nor a spare mouse. Any advice is much appreciated!

 

IMG_0936.thumb.JPG.aa659c9182bb515f7359ea6d63fa7457.JPG

 

 

Edited by nightingale
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“Up” and “Down“ is kind of a misnomer. It’s more like “Y1” and “Y2”: two sensors, slightly offset, watching the same (I think) LED. They’re not independent, and the computer can’t detect vertical motion unless both sensors are working. I’m not sure if you can get useful readings off the pins without powering up the mouse (and LED and sensors).

 

I haven’t opened up my M0100, but I think that if you were to plug the mouse in while opened up, you could observe:

  • the LEDs light up (possibly through a cell phone camera)
  • the Up/Dn pins go high and low as you roll the ball (I’m not sure I’d be confident enough in the steadiness of my hands to try this, though)

There’s not a lot of electronics in the M0100, so I think it would have to be the LED or one of the sensors.

 

I don’t know what you have available for testing. If you could wire the mouse to a breadboard, that would make things simpler.

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My understanding is that x and y-axis are generated through two sensors (sort of hall effects units)

 

So either the sensor is bad or the y-axis wheel is not turning freely when the ball is rotating.

 

try to rotate the wheel by hand when connected to the Plus.

 

Both shafts are driven by a rubber ring and contact is maintained by a metal spring, both can be bad.

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10 hours ago, bibilit said:

try to rotate the wheel by hand when connected to the Plus. 

  

Both shafts are driven by a rubber ring and contact is maintained by a metal spring, both can be bad. 

Agreed; I'd check mechanical things before trying to troubleshoot electronics.  Anecdotally, the optical sensors are very reliable, but the plastic rollers and springs can be questionable, and old age and grease can make the wheels seize up entirely.

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Thanks for the suggestions, everyone.

 

Mechanically, everything is working fine. I've hooked the cable back up to the board and booted the computer. I can move the wheel for left/right movement and it works, but when I move the wheel for up/down it still gives nothing.

 

I tried looking through the phone camera to see if it could see the sensors lighting up, but it didn't work.

 

I guess that narrows it down to the sensor(s) -- does anyone know if this was a common component in mice that might be widely available from any old donor mouse, or were they Apple specific? It's hard to tell from the photo below, but it looks like there is a little black clip holding it in place, in addition to being soldered to the board. It looks very difficult, though not impossible, to remove. I may attempt to use the multimeter while it's powered on, but like you said, it will take a very steady hand.

 

Before I go to that extent, can anyone think of any common issues with the Plus that might be causing this?

 

IMG_0937.thumb.JPG.7f0462295d3a89d782f0305fcb205ce6.JPG

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Okay, so I think I'm making some progress. As I'm not an electrical whiz, I'm hoping someone can tell me if I seem to be on the right track.

 

I powered on the Plus and checked some readings on the mouse. I'm getting 5V on the 5V pin. So far so good. The power for the LEDs go through 620 ohm resistors. Three of the four LEDs are reading approximately 1.2 volts, so the resistors seem to be doing their job. However CR2 ("UP") is getting 5V. So it is getting too much voltage.

 

However, when I test the resistance on the four resistors, they all read 607 ohms, which is within the 5% tolerance of the resistor, so that means they should all be good, right? If the resistors are okay, then the only conclusion I can come to is that there is something connecting one of the 5V traces to the trace that goes from the resistor to CR2. Except they aren't even close to each other, and I don't see anything that would be connecting them.

 

If the resistor is in fact good, can anyone explain why 5V is going in and 5V is coming out?

 

If I can figure out the voltage, I guess the next question will be did the extra voltage fry the LED...

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On 8/6/2020 at 9:46 AM, nightingale said:

No, I don't...

Sorry, I meant to reply to this yesterday but didn't get time.  I was going to say that you could work out which sensor was dodgy by putting 5v and ground into the mouse and looking at the signals coming out of the sensors, but it looks like you've already worked out which sensor is dodgy.

 

11 hours ago, nightingale said:

Okay, so I think I'm making some progress. As I'm not an electrical whiz, I'm hoping someone can tell me if I seem to be on the right track.

Yes, this is definitely progress.

 

It sounds a bit like it's gone open circuit to me?  How much voltage is dropped across the resistor will depend on how much current is flowing (Ohm's Law).  If very little current is flowing then the change in voltage across the resistor will be very low.  If the circuit is open, the only current flowing through the resistor will be through your multimeter, which will be a minuscule amount, and so there will be no noticeable voltage drop.

 

So—a good first step might be to resolder that component to see if it's just a joint that's gone bad, and check that there's actually a circuit between +5v and GND involving that LED.  Failing that, you might be looking at replacing the LED.

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So I just gave everything a good cleaning with 99% IPA. What a difference, there was much more gunk on there than I realized. Much easier getting readings now. Double checked everything. Still getting 5V between CR2 and GND instead of the expected 1.2V. I don't believe anything is shorted anywhere.

 

15 hours ago, cheesestraws said:

It sounds a bit like it's gone open circuit to me?  How much voltage is dropped across the resistor will depend on how much current is flowing (Ohm's Law).  If very little current is flowing then the change in voltage across the resistor will be very low.  If the circuit is open, the only current flowing through the resistor will be through your multimeter, which will be a minuscule amount, and so there will be no noticeable voltage drop.

 

And I'm now about to butcher all the proper terminology here, but hopefully everyone can get my meaning...

 

If I'm understanding you correctly, there may not be enough current flowing through the trace, which results in the voltage not dropping through the resistor.

 

There is one trace that goes from the 5V pin to everything that needs power. In order, it's:

5V > R4 > R3 > R1 > R2 > U1 > U2 > U4 > U3

 

Then the resistors send power to the LEDs.

 

I used my meter to measure current, but I'm not entirely sure I'm using it right. I checked across R1, R3, and R4 and got a reading of 1, and when I check across R2 (the problematic resistor) I get a reading of zero. I suspect I'm not using my meter correctly, but clearly there is something different about this resistor.

 

R2 is the resistor that is problematic, and it is the last resistor in the chain from 5V. So could it be that the current is dropping along this trace, so it has enough current for the first three resistors to work properly, but then not enough for the fourth? The optical sensors are all after R2, and are working fine (left/right anyway), but maybe the drop in current is not an issue for these?

 

Thank you for your patience as I try to figure this out!

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Um, that's not entirely what I meant.  I am not very good at this stuff, so if I am wrong, hopefully someone else will correct me.

 

What I meant was, if you put a voltage (in this case 5v) on one end of a resistor, and leave the other end flapping about in midair, and measure the voltage between the loose flapping end of the resistor and ground, it will be your original voltage (5v, in this case), because the voltage drop across a resistor is proportional to the current flowing through it, and if it's disconnected on one side, the current will be 0.  So, if you're seeing 5v between the bottom end of the resistor and ground, it means that that end of the resistor is effectively not connected to anything.  So it looks like the LED has failed in such a way that it's acting just like an air gap.  This could either be because one of the solder joints has gone bad on the LED itself, or because the LED itself has failed.  I'd try touching up the solder joints on the resistor and the LED first, personally, before trying to work out what to replace it with...

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Posted (edited)

Okay, I'm getting you now. I also talked to my brother-in-law who is an Engineer, and he helped me understand some of the principles at work here.

 

When I put my meter on the resistor and the ground pin, my meter was completing the circuit, not the LED, which is why there was minimal current, and why I was getting the 5V reading. I get what you're saying about the LED opening the circuit.

 

So I am quite confident now that the problem is with the LED. I will try just resoldering this one in case it's a bad connection, otherwise I'm off to go find some other mice to see if I can find a donor LED that is the same as this one... Hopefully Apple was using some standard parts in these mice that are common to other mice from that era.

 

Thank you for all your guidance, @cheesestraws, it was very helpful. If nothing else, this has been a valuable learning experience.

 

On a side note, since I had the mouse apart, I made my first attempt to retrobrite something. I used the oxiclean method that a few people have been experimenting with lately. I left it out in the sun for two days of about 30 degree Celsius (~86 F) weather. It came out a bit splotchy, but the extra white areas appear to be where the texture of the mouse is worn down from use, so the results may have been the same with any method. It's definitely still a bit yellow, so I may try it again with another method at some point, but I'm happy enough with it.

 

20200806_203120.thumb.jpg.4e3e8d5553247ad92376bd2dd7d3b61b.jpg

Edited by nightingale
fixing @ mention
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13 hours ago, nightingale said:

Thank you for all your guidance, @cheesestraws, it was very helpful. If nothing else, this has been a valuable learning experience.

You're very welcome.  I'm sorry my explanations leave a certain amount to be desired; I'm not good enough at this to explain it really clearly.  I'm glad you've learned stuff; for me, at least, that's half the point of this hobby to start with.

 

You may well find that Apple used a pretty standard infra-red LED in there; there's no reason why they would use something particularly special or magical.  So you might well be able to get a reasonable new replacement.  This would probably last longer than one from another mouse (though would not be so "authentic", whatever that means), and probably easier to get hold of for cheap.

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I opened up my ’84 M0100 to take a look, and found it to be rather different:

 

MVIMG_20200810_120750.thumb.jpg.85bfb7e517c757c59cf1e5760de530e8.jpgMVIMG_20200810_120940.thumb.jpg.807768c848df352feb4d1a04ff1f9937.jpg

 

The most notable difference is the addition of the chip on the upper right, but also significant is the replacement of your 3-pole U1/2/3/4 with two-pole Q1/2/3/4. I’m not very knowledgeable about circuitry, but based on a little searching, my chip seems to be an inverter, and my guess is that your mouse has four phototransistors, whereas mine has four photoresistors (and an inverter to bring the signals to logic level). I’m not sure what the component on the left of mine is (labeled “DALE 1-103G 8434”).

 

Unfortunately, the differences probably make it harder to diagnose problems by comparison. Your mouse is impressively old—I was surprised to see ©1982 on the circuit board. Mine is serial G447M010009998 (mid-November 1984) which I already thought was plenty old.

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On 8/10/2020 at 2:30 PM, sfiera said:

The most notable difference is the addition of the chip on the upper right, but also significant is the replacement of your 3-pole U1/2/3/4 with two-pole Q1/2/3/4. I’m not very knowledgeable about circuitry, but based on a little searching, my chip seems to be an inverter, and my guess is that your mouse has four phototransistors, whereas mine has four photoresistors (and an inverter to bring the signals to logic level). I’m not sure what the component on the left of mine is (labeled “DALE 1-103G 8434”).

 

When I opened up my mouse, I was surprised by the simplicity of it. The 1982 date would mean this mouse was used for the Apple II series. I assume the additional components on your model must be intended to improve the accuracy of the mouse. Every other mouse I've looked at the inside of has at least one chip, so presumably this was an improvement over the earlier design. It does appear that the IR diode remained the same in later models, so hopefully that means it will be easier to find a replacement.

 

I picked up a new soldering iron this weekend, so I'll be attempting to deconstruct this thing this week, although it looks as though the component is clipped in somehow, so hopefully after the solder is removed it will be come apparent how to remove it.

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