Agree to the self resetting thermal switch, seems to be most likely this
one.
Regarding the 9W power adapter: it is a highly sophisticated switch mode
power supply with two main modes:
constant voltage mode of max. 7.5 Volts (as long as the current is below
1.3 Amps)
constant current mode limited to 1.3 Amps (the voltage goes down in order
to keep the current constant)
In case of the load is even more low impedant, the power adapter will fold
back the output current.
In my experience this adapter is perfectly matched to the Newt, thats why
you will not achieve the same quick charging behaviour with a laboratory
power supply or any ather wall plug adaptor.
Johannes
-----Original Message-----
From: Andrew Beals [SMTP:bandy_at_cinnamon.com]
Sent: Wednesday, January 23, 2002 6:45 PM
To: newtontalk_at_newtontalk.net
Subject: Re: [NTLK] Resistant thermistor
On Wed, 23 Jan 2002 18:29:06 +0100, "Gruendel, Frank 3837 S-WF-RD6"
<Frank.Gruendel_at_de.heidelberg.com> wrote:
>
> Yes, this IS Newton related, because the outcome of this discussion will
> control whether I need to update my refurbishing instructions or not :-)
>
> > I am not really happy with the terminology for "thermistor" what is in
> > my opinion most likely a thermo-fuse and for "resistor" which should
read
> > thermistor. Of course every resistor will change its resistance with
> > temperature, but while this is a side effect for resistors that may
cause
> > trouble in your circuit, this effect is especially distinctive and
> intended
> > for thermistors, because they are used for sensing temperature.
>
> I'm inclined to agree. When I encountered this "thing" (which I so far
have
> called a thermistor), I found a pdf datasheet where (I think) it was
> called a thermistor. I will look if I can dig it out.
> Is a fuse in the English language an element that can only cut a
connection
> (because the wire in it has melted),
Correct. A fuse is a use-once device. Murphy tells us that to save the
$0.05
fuse, a $20.00 part will blow instead.
> or would a component that cuts and
> re-establishes a connection be called a fuse, too? Personally, I would
> probably call a component like that a switch.
Way back in the '70s, that would be termed a self-resetting thermal
switch/breaker/relay.
> > and in my opinion you can leave it out with no doubt as
> > long as you use the original power supply or a power supply with less
then
>
> > 9W power.
>
> If that was true, Apple wouldn't have put it in in the first place.
So long as they could depend on the 9W ps staying at its rated capacity.
Is
it a switching supply or just a typical "wall wart" transformer? Switching
supplies have a failure mode where they go overvoltage! Depending on a
regulated ps to stay regulated is not prudent.
andy
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