EEVblog #418 - Mailbag Apple Newton Teardown

Mailbag time.
Dave tears down an original Apple Newton Messagepad 100.

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[MrYoshiDan]

Hi Dave. I know I'm waayyyy too late to respond to this. Like 4 years too late. Meh.

I collect vintage computers, and I've got a few newtons which had the exact same problem that it this one looks to have.

There's two electrolytic caps on the board that at first glance look like surface mount tantalums (actually, at 12:22 you pointed one of them out and said it was a tantalum). I found when looking closer at mine that they're actually tin cans inside of a plastic package. One is a 100uf used on the speaker output (which isn't really a big deal), and another on the rear side of the board -- you can see that one in the video near the PCMCIA slot around 15:30.

On my Newtons, I found that they had leaked pretty badly. It looks like the ones on this one have too; there appears to be a some gunk around that 100u cap near IC4. Also, what looks like flux residue near where the speaker wires are was leaked goo from that cap on mine. Can't say that that's what it is in this one, but I'd give all of that a good clean and replace those two caps. I find replacing those two as well as the big 470uf one gets them going again.

I shoehorned in some radial through hole caps on mine because I had no idea what the type of surface mount electrolytic caps are called in this form, and I couldn't find any replacement ones. Eh, if it's stupid but it works, then it's not stupid. Actually it's still stupid. But it works. Meh.

[mikeselectricstuff]

Secret blue switch is probably battery type detect - there is probably a rechargeable option to replace the AAA holder. Hence the temp sensing as well.

[Reparaturkanal]

AFAIK, it holds 4 AA batteries.
You can't slide the orange slider when you've removed the battery holder.
One of the "secret" switches recognizes if you've inserted 4 AA batteries or a rechargeable battery pack. If the latter is recognized, it will charge it when you've got the power adapter connected.
If you know how, you can display the thermistor temperature in the menu. It is quite accurate if you're not recharging the battery pack.

[SirMo]

Apple always took pride in their products. That looks pretty amazing for 1993.

[therealjammit]

Hey Dave, just a heads up:
The LTC902 was Appletalk chip. The non Apple version sold as a LTC1320.

[Lachlant]

According to MacTracker the DIN port is a LocalTalk RS422 port. The Apple Newton could charge a rechargeable NiCad battery pack, I suspect that blue switch inside the battery compartment detects when the rechargeable battery is installed and allows the Newton to recharge the battery.

[InsurgentX]

The LTC902CS appears to be an RS422/RS562 line transceiver designed for AppleTalk networks. That was apparently a custom Apple version but the commercial equivalent is the LTC1320 which you can find datasheets for.
If this info is wrong, blame the Internet ;)

[tablatronix]

The blue switch detects rechargeable battery pack or cell pack if i remember correctly, it also has a temperature sensor in the battery compartment.

[dbtest]

The Serial connector may be odd, but it should be a RS422 or RS423, so not so custom Apple stuff. Not just the typical RS232 you find on "lower class" hardware. 

[mactek]

The primary software developer on the Newton was known for constantly adding new hidden features to the software even after it was supposed to be frozen for production. One of the easter eggs was a software thermometer that used the thermistor circuit next to the battery.

[BlaineMurphy]

Use the diodes for diode-resistor-logic gates, you might have enough to make a sizable ALU.

[criggie]

I had a MP100 and later was given a MP120 and a MP2000. The battery pack was rechargeable, OR you could use primaries in that little holder. 4xAAA would last anything from 2 to 4 hours of usage, so it wasn't cheap to run. Also it wouldn't work at all on rechargable AAAs because back then it was NiCD with 1.2V. I reckon the authentic Apple pack had 5x 1.2V = 6V to keep up with 4x 1.5V disposable batteries.

The orange switchery was a lockout to prevent you from taking out both batteries at once, so to keep the memory powered. Of course both could still go flat in place.

[rfvtgbzhn]

7:20 It's interesting that an Apple device was powered by AAA-batteries. This is very different from what they do today, now you cannot even Exchange the battery on an apple device without doing an almost complete disassembly...

[morelenmir]

I cannot say how much I wanted one of those, back in autumn 1993!!!

Looking forward to the repair video - I'm guessing in this case it WON'T be the electrolytic capacitors at fault!

[pmgodfrey]

I bought one of these in 1994 and hardly used it. Still have everything boxed up and it works too! Super slow handwriting recognition by todays standards. It was a fun toy...but that was about it.

The interface cable and it's software were sold separately and from what I remember, it wasn't cheap. This was back in the day where 16 meg memory modules cost upwards of $500 USD!!!

[Wesleyrpg]

Dave, did you ever get this thing working???

[memadmax]

I remember flipping thru the apple store magazine way back in the day and wanting one of these so bad...
I even started mowing lawns non stop for a couple of months...
Ended up spending the money on parts for a 486 system lol

[retrobrw]

Hmmm. I recognize those boxed SMD Electrolytic capacitors in that Apple Newton. Those are the reason that Sega Game Gears found in the wild don't work anymore!

[Awesomepotamus]

the blue switch is the main battery detector. the black switch is part of the locking mech that won't let you switch the orange switch unless there is a battery in either the backup slot or the main slot. so to change the main battery you switch it over to replace main and swap the battery, to swap the backup you do the reverse. as you said it was part of the design to maintain data.

[Gameboygenius]

You could, but 1n4148 are signal diodes with a low reverse breakdown voltage. These are rated 70 V as you can see in the video. So they would pop long before you would reach any kind of "fun" voltage.