> Can you exactly descibe which part you mean (part type, part number,
value,...)?
>
> I have one of those MP130s that died in my hands. But it had nothing to do
with
> drained
> batteries, it must be something else, maybe a defektive part. The
batteries where fully
> charged, when the Newton died.
I am still fairly unsure as to what causes this behavior. I have sworn to
myself,
though, that I am going to find this out even if this is the last thing I do
on
this planet. My oscilloscope is looking forward to the days after
Chrismas...
I have ruled out a couple of things by now, however.
1: It is not the display unit. I've tested two machines showing this defect
using intact display units and nothing changed.
2: It is not the small pcb that sits between the main logic board and the
battery compartment (and is connected through the ribbon cable to the
mainboard. I've replaced this on a machine to no avail.
This defect comes in different flavors. What (I believe) is common to most
of them
is that the Newton power manager thinks it should shut the Newton off at
some
earlier or later time. This can happen out of the blue, immediately after
turning
it on, after some heavy use, when you switch on the backlight or any other
time.
Very severe cases don't even load the os, but shut off immediately after
turning
the Newton on. Most severe cases don't even allow the Newton to be turned
on.
I am in fact not sure whether Newtons that "die" out of the blue really die
or
whether a defect they had for a long time suddenly manifests. I'm inclined
to
assume the latter is the case. I have a 130 that always shut off 2-3
seconds after being turned on. I removed the mainboard, had a look at it
under
a microscope and put it back in. I have never been able to turn this 130 on
ever after, probably because the mainboard is now in a position marginally
different from that it had before, maybe it is bent a trifle more or less
due
to some screw being more or less tight or whatever.
The latest machine I experienced this problem with would work fine for a
long time unless I slightly pressed with a pencil on a spot above the
switching regulator (the IC at the bottom right corner if you look at the
mainboard with the battery case pointing towards you). "Slightly" in this
context meant "about as much pressure as whistling at the board would
have applied". If I put a piece of cardboard beneath the mainboard (below
the
regulator) to push it up a bit, I could still trigger the shutoff, but I
needed much more pressure. After some time, though, I couldn't get it back
to work at all.
Someone else I've been in a long mail contact with reported he was able
to fix this problem by increasing the pressure on the ribbon cable that
is in the connector where the switching regulator is, plus pressing the
board down a bit.
Others have reported they could fix it by re-soldering some soldering
joints in that area.
Common to all these reports is that the problem seems to be located around
the ribbon cable connector and the switching regulator. This matches
my own experience.
My guess, though, is that all these attempts basically did the same
thing, namely moving the mainboard ever so slightly at a place where
it needed to be moved for exactly the amount required.
Another standard problem 130's have supports my bad mainboard theory.
There's another standard fault that results in the contrast changing
at the slightest movement of the Newton. Two of these I was able to
"fix" (if you can call it that) by glueing a small plastic part close
to the power switch that presses the mainboard slightly down when the
back part of the case is put back on. On a third Newton I had no
chance. I took the mainboard out (because then I didn't know the plastic
part trick) for looking at it under the microscope, put it back in,
and the contrast problem was gone. Well, sort of, as I have never been
able to get this particular 130 back to life again. Probably because
problem #1 had hit me...
If ever I should be able to read minds, Dr. Newton's will be the
first I'm going to give a try...
Until then, all you out there, keep trying to find a schematic for
the 120 or 130, I'll pay with the finest German chocolate there is ;-)
If you want me to have a look at your 130 for free, go ahead. All you'll
pay is return shipping. If your particular Newton helps me to finally
find the reason for this mysterious defect, shipping will be on me...
Frank
Newton software and hardware stuff at www.pda-soft.de
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