Warning: This post is a little long. And occasionally a
bit technical. Then again, maybe the info is interesting for
you. I do think that even if it isn't, it might be nice to
read.
The following production has cost me one solid week's worth of nights...
##### Cast listing: #####
Frank Slightly dumb hobby service technician who earns
his living
by pretending that he is a programmer
Paul The incredible Guyot, technical adviser
Dale Mainboard provider
Andreas Mainboard provider
Martina Amazingly patient wife, who has every right to expect
other
activities at Easter
##### Crew listing: #####
Misc. Apple Newton hardware developers who could have
prevented all this
Microscope Located in Florida. Bought from Germany in an
eBay auction,
sent to a colleague's sister's house in Florida,
picked
up there on the occasion of a holiday trip and
lugged back to Germany
Weller WSD 50 Frank's wonderful soldering station
Voltcraft 3650 Frank's multimeter
BeeOne, BeeTwo 9 Volt batteries for multimeter
BeeThree 9 Volt battery, because two aren't enough for
such a project
Reddy and Blacky Tiny test probes bought for this very project at
EUR 15.00 each (ugh...)
Gossen Model 1 Frank's decades-old adjustable laboratory power supply
##### Awards: #####
None
##### Home video releases: #####
None
##### Plot summary : #####
(Spoiler warning: This will unravel one of the most mysterious Newton
mysteries).
Set in 2006, the story begins with Frank's getting yet another Newton on
his workbench that
shows a classic defect: The Newton tries to power up, chimes, changes
his mind,
switches off again and starts over. Usually this is repeated twelve
times, then the
Newton gives up.
The defect in question used to be repaired by David Watson, also known
as Dr. Newton.
Unfortunately, David seems to have dropped off the surface of this
planet, making it
impossible to get at information that would be necessary to fix this
problem.
Up to the day that marks the beginning of the story, Frank has never
been able to fix
such a board. He has always had to replace them. The result is a small
cardboard box
containing 5 Newton 2000 / 2100 mainboards that all suffer from the same
disease.
Frank briefly contemplates making the 6th one join its 5 unfortunate
pals in the box,
but changes his mind. Preparing and accomplishing a large-scale
expedition to fix one
single Newton mainboard would of course make no sense whatsoever. Frank
could make much
more money in much less time by pretending to be a programmer.
On the other hand, preparing and accomplishing a large-scale expedition
to fix SIX
Newton mainboards would make no sense whatsoever, either. Frank could
still make much
more money in much less time by pretending to be a programmer.
As a consequence, Franks starts preparing a large-scale expedition
into the depths of Newton hardware. Comparing every single component on
a dead board
to it's respective component on a working board isn't exactly a
professional way of
doing service, but with no technical information whatsoever at hand it
is the only way
available to dumb service technicians.
The next day sees Frank putting a Newton mainboard on his employer's
copy machine
and experiment with different settings until he has a decent photocopy
of each side of the
board, enlarged to a size of about 0.4m by 0.3m. After all, even a dumb
service technician
is aware of the danger of forgetting which of the hundreds of components
has
already been tested and which hasn't, so he wants to mark the tested
ones on the copy.
On his way home Frank secures himself to BeeOne, BeeTwo, BeeThree, Reddy
and Blacky.
0.24 square meters of table space not being available close to the
workbench, Frank
tacks the copies to the wall, resulting in his wife's tendency to frown
with the
facial expression of someone suffering whenever she passes them, which
happens approximately
twelve times per hour.
To save time Frank decides that, while he is at it, it would make sense
to not only compare
two boards, but three, the third one being one that has another standard
defect: The Newton does
not start up. Brainwipe works, but the Newton never starts up after it.
Frank has an inkling
that these two defects are only two different results of basically the
same problem.
Equipped with three 2100 boards and a pen Frank fires up his trusty
multimeter and sets out
on his leap in the dark. For a start, he decides to measure and compare
only standard
semiconductors like transistors and diodes. Resistors die far less
often, the death of electrolytic
capacitors is usually visible and smellable, small capacitors hardly
ever die at all, and the
sheer amount of pins of integrated circuits is likely to make him give
up before he started.
Two and a half nights later all diodes and all transistors have been
compared. Unfortunately,
nothing out of the ordinary has been found.
The logical choice would now be to start comparing the integrated
circuits. But the amount
of pins dejects Frank, so he decides to have a go at the resistors.
He strikes gold at about 3am during night #3. R120, which should have a
resistance value of
36kOhm, has a resistance value of 70kOhm. Replacing it fixes this
particular mainboard, which
will make cast member Dale G. very happy because Frank has promised to
fix his Newton for
free if his mainboard happens to be involved in a successful outcome of
Frank's crusade.
Overwhelmed by his success, Frank decides to call it a day and sleep a
bit for a change.
As of then there's one mainboard less to compare. The bad news is that
there's still
one left, because R120 is perfectly healthy on the boards with the
repeated boot attempts,
of which Frank still has six.
However, one leg of R120 is connected to a bit of circuitry around a
Maxim MAX1771 chip, which
is an adjustable high-efficiency DC-DC controller. The design around it
is in exact accordance
with one of Maxim's application notes for this circuit, which allows
Frank to determine that the
Newton developers have intended the output voltage of this circuitry to
be 5 Volt.
This voltage is missing. Unfortuntately, it's missing on the working
board, too. It
doesn't seem to be THAT important. Hgrmpf...
Now the incredible Paul Guyot enters the picture. Having always admired
his amazing knowledge
of the internals of the Newton OS, Frank has a long time ago asked him
if he has an idea what
exactly happens at the end of the startup chime (remember that the
Newton always powers off immediately after the chime). Back then the
incredible Paul Guyot had
answered that the Newton is checking the presence of a voltage required
for the PCMCIA card
slots. Back then Frank had compared the slot connectors of a dead and a
working board and handn't found
any difference.
But...
5 Volt is a voltage that IS required for some types of cards. So Frank
checks if there
are any PCMCIA specific ICs on the board that might handle the slots'
voltages. This is a rare
streak of genius for a dumb technician, because he finds one SI9712 chip
for each PCMCIA slot.
This is basically a switch matrix that routes 3.3 Volt, 5 Volt or 12
Volt to the card slot pins.
Frank measures that the 3.3 Volt and 12 Volt are present, but the 5 Volt
aren't. Unfortunately,
they aren't present on the working mainboard, either. Hgrmpf...
By another rare streak of luck Frank has another look at Maxim's
application note and notices
that the MAX1771 has a shutdown pin. Since the Newton usually shuts all
unneeded voltages off
to save power, it would make perfect sense to shut card-related voltages
off until they are
needed. Which leads to the third streak of luck, namely Frank's
measuring this voltage while
the Newton is powering up instead of when it has done so.
Lo and behold, on working Newtons the 5 Volt supply is turned on for
about 2 seconds, probably
for allowing the Newton to check that it is there) and then turned off
again. On the dead
mainboard the 5 Volt supply is NEVER turned on.
The question now is whether this is because on the defective board the
Newton doesn't switch
the MAX1771 on, or because it or the circuitry around it doesn't do its
job anymore.
Drunk with happiness Frank decides to be unable to concentrate any
longer and hits the sack.
This is the end of night #4.
The next day Frank does something that should only be done if... if...
well, actually,
it should NEVER be done. He sets crew member Model 1 to 5 Volt and
connects its output to
the output of the comatose MAX 1771. After having made sure that the
fire extinguisher is still where
it used to be, he switches both the Newton and Modell 1 on at the same
time.
Nothing happens. No sign of life whatsoever. No smoke, either, but a
totally
dead mainboard. F*ck...
This is the end of night #5.
One night later. Frank notices that there's no ROM board in the
mainboard. He had removed
it for his soldering and completely forgotten about it. Slightly ashamed
of himself he puts it back
and repeats last night's experiment.
Lo and behold, the Newton powers up. No more cyclic boot attempts
anymore, it just powers
up like it should and smiles at Frank. It even stays on and works hunky
dory if Model 1
is disconnected after the powerup (unless, probably, although Frank
doesn't try this out, cards are
inserted).
This, quite obviously, is a major breakthrough. Although it doesn't fix
the defect, it allows
to power the Newton up in a way to backup people's data, which so far
has never been possible.
This is the exact time when Frank decides to change his schedule at
short notice and insert
an hour of celebration in company with a couple of bottles of decent
Single Malt scotch
whisky. Since this hour somehow becomes a bit more than just one hour,
this is the end of
night #6.
The last roadblock now is, of course, finding out WHY this voltage is
missing on the
defective mainboard. Frank decides to approach this problem in a
somewhat pragmatical
way by simply replacing the MAX1771. By now he firmly believes to be
kind of entitled to
a little success that hasn't cost him nights. Greedy as ever (and
because it's Sunday and
there's no chance to buy a replacement), Frank cannibalizes a MAX1771
from an organ donator board
and solders it on the defective board. He then makes sure that the ROM
board is where it
should be.
Biiiiiiingooooooo...
This is the end of night #7 and the beginning of another celebration
session.
Final scene. Frank, humming under his breath, has just finished fixing
mainboard #6. Every
single one of these six fellows has been fixed by replacing U34.
Heard it? U34!! MAX1771!!!
Boy, one of these days I will start accepting donations...
Frank
-- Newton software and hardware at http://www.pda-soft.de
-- This is the NewtonTalk list - http://www.newtontalk.net/ for all inquiries Official Newton FAQ: http://www.chuma.org/newton/faq/ WikiWikiNewt for all kinds of articles: http://tools.unna.org/wikiwikinewt/Received on Wed Apr 19 20:43:28 2006
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