### Author Topic: EEVblog #418 - Mailbag Apple Newton Teardown  (Read 17085 times)

0 Members and 1 Guest are viewing this topic.

#### hli

• Regular Contributor
• Posts: 215
• Country:
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #25 on: February 12, 2013, 01:40:22 pm »
The LTC902 is an AppleTalk transceiver. (I found it in a Maxim cross-reference list, which lists it as compatible with the MAX216 - and there are data sheets availbale for this one).

There is a service manual for the original MessagePad available. It states the model number BO-A300, but this should be the same as the H1000. It also explains what this large ASIC does - and it has a chapter on diagnosing power-on faults (page 31ff).

#### kfitch42

• Frequent Contributor
• Posts: 300
• Country:
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #26 on: February 14, 2013, 06:07:33 am »
Caveat: I am a software guy, so anything I say here might be incredibly stupid...

With all those diodes you could make the worlds most ridiculous A2D converter

Use an op-amp to boost the input up to a pretty high voltage
Then in parallel you have 1 diode, 2 diodes in series, 3 diodes in series, 4 diodes in series ...

Each time the output of the op-amp goes up by another diode drop (0.6ish V usually, right?) another string of diodes lights up.

To make a n-bit a2d in this way would require (2^n)-1 strings. Using Gauss's summation we see that
((2^N)-1)(2^N)/2 = 2^(2N-1)-2^(N-1)

So to make a
1 bit a2d requires 1 diode,
2bit requires 6,
3bit requires 28
4bit requires 120
5bit requires 496
6bit requires 2016
7bit requires 8128
8bit requires 32640

#### EEVblog

• Posts: 32339
• Country:
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #27 on: February 14, 2013, 07:59:51 am »
There is a service manual for the original MessagePad available. It states the model number BO-A300, but this should be the same as the H1000. It also explains what this large ASIC does - and it has a chapter on diagnosing power-on faults (page 31ff).

It was manufactured by Sharp?

Dave.

#### hli

• Regular Contributor
• Posts: 215
• Country:
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #28 on: February 19, 2013, 03:36:11 pm »
It was manufactured by Sharp?

At least the original one, yes: http://en.wikipedia.org/wiki/MessagePad , though I'm not sure about the MessagePad 2000 series.

#### rain

• Contributor
• Posts: 5
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #29 on: March 25, 2013, 06:39:38 am »
Yowza.  Is that EMI at the end of the video (~19:30) messing with the camera?

#### haxtormoogle

• Contributor
• Posts: 7
##### Re: EEVblog #418 - Mailbag Apple Newton Teardown
« Reply #30 on: October 16, 2013, 08:36:24 pm »
Yowza.  Is that EMI at the end of the video (~19:30) messing with the camera?

Yeah what is up with that video distortion? looks to stop when you hit the power button?

On closer look at the video tr5 looks blown.

Looking from the service manual

tr5 is a major component in the 5V stabilizing circuit. If tr5 is burned out then it will not power on.

Would be need to see a follow up on this to see if this really is the problem
« Last Edit: October 16, 2013, 08:44:02 pm by haxtormoogle »

Smf