Apple Newton MP2100 Repair

[revo8778]

Hi. I have an Apple Newton MessagePad 2100. Inside of it is a small, battery-like device that powers the clock when the main battery is removed. However, my clock is always wiped when the main batt goes dead, so I figured this clock battery needed to be replaced. However, upon further research it seems that this battery I found might actually be a capacitor. It's labeled [M] GC5.5v0.10F. Can anyone here confirm if this is a capacitor or not?

I can provide pictures if necessary.

 

[Resqueline]

Yes, that's a so-called super capacitor, often used for memory backup etc. It tolerates up to 5.5V and has a capacitance of 0.1 Farad. They can go bad.

 

[MattyMatt]

I've seen these in some strange older laptops, there may even be some newer ones out there I think the [M] has to do with Mashushita (manufacturer) who is the main company of Panasonic.

On a side note, I think is really cool you still have a old Newton, they were fantastic!
Matty-

 

[revo8778]

@MattyMatt Yes, and I love using it too. Compared to modern devices, it's in a league of it's own.

Honestly, I'm not even sure if this capacitor is actually responsible for clock keeping, although it would make sense if it were. After I removed it to get the label off of it, the MP2100 would still boot up and work as normal. Weird...

After 11 years, could this cap have gone bad? I was under the impression that most caps last about 20 years before failing.

 

[Resqueline]

Those kind of cap's are basically chemical in nature and as such they don't seem to have much longer life than a well-tended battery.
A computer can often boot w/o the clock/cmos battery, and keep time when powered, but I don't expect the MP kept the time after you removed it (and turned off power).

 

[revo8778]

So it might as well be a battery. Huh, I wonder why they didn't put in a Li-ion button cell to begin with.

I suppose I should find a replacement then. I can't find a source for these 5.5v0.10F caps, but I've found numerous sellers of 5.5v0.22F caps. Will the additional capacity be a problem or is it a fine replacement for the old cap?

 

[Resqueline]

It's a sad fact, but I've seen big versions of these fail before 10 years of age. I'm sure they were intended by the manufacturer to last longer though.
Doubling the capacitance should not be a problem.

 

[MattyMatt]

So it might as well be a battery. Huh, I wonder why they didn't put in a Li-ion button cell to begin with.

The big reason is probably because the Lithium Ion cells at the time were not as effective as we have today (at least that's what I recall). Not to mention, size, voltage and honestly, the gain of using that chemistry vs. a decent super cap.... it was probably not very viable at the time, and it probably would have had the same problem at this point.

As far as any kind of value changing, i'd ask Res on that one, I'm more of a beginner myself... at least on certain things

Edit: Wow, never mind, Res already answered, shows i can read.... ::smacks forehead::

Have fun!
Matty-

 

[(*steve*)]

Capacitors are actually better than batteries in some cases.

In this case, you can let them go dead flat without damaging them, and aside from limiting current and peak voltage, charging them requires no special circuitry at all.

You should be easily able to find a replacement. I'd suggest that even a 5V 1F (i.e. 10x the original capacity) supercap today will probably be the same size or smaller.

Getting something that you can make fit will be the major issue.

Do you have the dimensions of the original? And where the connections were on it?