A Request to all the list members:
I think I have the answer to the many problems I've watched discussed on
this list about the confusing symptoms people have been finding in their SM's.
Please help me with my thinking of why I might want the Cuda reset with
power on--and criticism is welcome:
It has been established that battery failures or low batteries give rise
to all sorts of goofy and apparently unrelated symptoms. These have been
frustrating and many people are innocently looking at other components
when in fact it is the battery that is the problem.
Their next troubles are that essentially no one has a spare battery or a
voltmeter laying around and it's difficult to get to the battery or its
terminals without taking the machine apart.
Therefore, while having a bad battery, we need a troubleshooting
technique that won't include a voltmeter or another new battery at that moment.
________________________________________________
The Cuda manager is a chip that holds the basic startup instructions for
power, video, etc. inside its PRAM in the max and macs. It also holds
owner-selected information on how their system runs. The memory inside
the Cuda is maintained by the battery, whether or not the computer is
plugged in, and a low or dead battery can corrupt the stored information
causing startup problems.
One correction for corrupted PRAM is to Zap it through through software
by the keyboard upon startup or using a utility like Techtool. The
penultimate correction is to push the Cuda reset on the motherboard
which is not software dependent, but gives us the same corrections.
It is likely that the default settings for the PRAM are stored in a ROM
(read only memory) somewhere and are copied when the PRAM is zapped or
the Cuda button is pressed. This action however requires voltage--and it
should be voltage at the proper level if the new settings are to be
properly copied.
If the low battery voltage gives us corrupted or lost settings in the
first place, why should that same low voltage give us proper settings
when we push or zap? I submit they may, but probably not as evidenced by
many people continuing to have the same symptoms after zapping and
pushing.
Now JR would agree, I think, that we can't get out of the vicious circle
if the voltages aren't there to exactly copy the read-only-memory. With
a new battery, it would work, but we don't have a new battery yet. We do
however have the battery charger circuit, which by design, should be the
proper battery voltage with a selected charging current for our specific
battery (Rayovac 840).
Now most all the recommendations I've read for resetting the Cuda switch
instruct us to first "shut off the mac," which is probably driven by a
concern for personal and component safety. But if we shut off the power
before pushing the switch, then the only voltage available for the cuda
reset is the bum voltage from the battery that is already causing problems.
Therefore, I submit as a point of discussion that resetting with the
power on gives us a faux battery in the form of the battery charger that
is already designed to be close to the specs of the battery in order to
charge it properly. This proper voltage has a much better chance to give
us a proper reset.
Well, you may ask, why is it that this won't happen in the ordinary
course of things and the charger would always take the place of the
battery?
The answer probably lies in the design of the charger circuit. A bad
battery can have internal shorts that would overload and overheat a
charger connected to it. A battery is replaceable, but a burned out
charger means a new motherboard, so various protective circuits are
designed in to keep that from happening.
One is called a crowbar circuit which classically shuts down or limits
the charger output if it is going to get in trouble. If that crowbar is
in operation in our charger circuit, the charger won't put out the
proper voltage and can't act as a faux battery.
So, here's my proposal. I'm not telling anyone to do this now! We are
thinking it through together for your comments and criticisms.
___________________________________________________________
When you can't get your Starmax started... (Rough draft of possible text)
(1) If there are problems like no-power up, no-video,
no-drive-recognition, and you tend to putter inside your mac or clone
anyway. And since you can't get the machine started to zap the PRAM by
the keyboard or by software either. Pull out the plug, open the case,
take off your rings, ground yourself properly to discharge any static
electricity, and then press the little red cuda reset switch.
(2) Put everything back together and see if it starts. If it does come
back to being a mac, go to a store, buy an Rayovac 840 battery and put
it in right away because the problems will be returning, you can bank on
it. The max wouldn't have gotten in this state unless the battery were failing.
If it doesn't work and the machine still won't start, repeat step 1 in
getting inside, but now we mark and unplug all the cables and harnesses
in order to draw out the motherboard and gain access to the battery.
Disconnect the battery, take it off its velcro pad and check the
voltage. If it's below 4.5 volts, get a new battery.
If you can't check the voltage, simply put the battery aside, reinsert
the motherboard, and reconnect the cabling.
(3) Plug the mac in, but don't power it up from the keyboard or front
panel switch, just simply plug the cord into the power supply. Wait a
few minutes, then press the red Cuda switch with the eraser end on an
ordinary lead pencil. This action allows the internal battery charger to
provide power for the proper resetting of the PRAM instead of having a
possibly bad battery try to do it.
Now reconnect the monitor, etc. and try an ordinary power up. If it
starts as usual, the battery was bad and you will need a new one.
If it doesn't and has the same symptoms, you may have a component
problem, but in any case have someone check the battery voltage and if
it is low, get a new battery.
All of the above is meant to keep you from mistakenly chasing the many
symptoms of a bad battery that imply a failed component. This route can
be frustrating and expensive. The most common and expectable failure in
a Starmax is its battery. The Motorola line is rather robust and most
components have a long life. It was always expected that batteries will
need to be replaced, This may be the time for yours.
Remember always look to the simplest and most expectable problem first.
Statistics give us the battery as the probable culprit, but sometimes
the symptoms can keep us from seeing that.
Good luck,
Bob Wulkowicz
____________________
This is my proposal which I will try on my own machines. I'm not
suggesting anyone try it right now, just think about it and tell me
where I'm mistaken or where it can be improved. This is an ordinary part
of the design and engineering process.
I am also pretty sure I have a way to predict a failing battery through
some software routes--which means you can probably get a battery before
the symptoms appear--wouldn't that be a pleasure.
Bob
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