From: James (orialv21_at_mindspring.com)
Date: Thu Jul 22 1999 - 01:39:27 EDT
No no... I am not saying the AC adapter will fail, I was refer to the fact that "more amps is not always better" in general - or from a device or EE engineering point of view. As my previous posting said, it is "not always better."
As my posting indicates, I didn't refer or make reference to the AC adapter.
----- Original Message -----
From: Bill Morrow
To: James
Cc: jclerm_at_aztec.asu.edu ; thinkpad_at_cs.utk.edu
Sent: Wednesday, July 21, 1999 9:09 PM
Subject: Re: Interesting TP accessory prices
ummm...
as a practical matter, i have and will continue to use AC adapters >from the 755, 701, 560, 600 and various 770's and any or all of the preceeding machines.. with, to date, no apparent thermal damage..
in fact, i have not had to send any thinkpad (yet) for service due to electronic failure..
James wrote:
Bill and Juan-Carlos,The point I was trying to make is that "more amp is not necessary better than less" as Bill have indicated in his original posting. And the reason is because it causes thermal breakdown. Thermal breakdown occurs when there is an excess amount of current across a cross area of a conducting medium per unit second. In semiconductor language, what this means is that the current causes an the rate of charge separation is faster than the rate of recombination. Above all, the point is that "more amp is not necessary better," a concept that all devices or electrical engineers should know. Like what Juan-Carlos said, assuming resistance is constant, then the voltage across the device determines the amp passing through it. ThanksJames
----- Original Message -----
From: Juan-Carlos Lerman
To: James ; thinkpad_at_cs.utk.edu
Sent: Wednesday, July 21, 1999 3:59 PM
Subject: Re: Interesting TP accessory prices
orialy21 said:
> In most cases, more amp is not better because it could
> lead to thermal breakdown unless your device is
> designed to run on reverse bias - as some diodes are.
Can you explain what do you really mean and how
does it relate to the problem?
It's my (poor) understanding that the power adaptor
is a constant *voltage* source, not a constant
*current* source.
In consequence the amperage drawn from it is only
dependent on the resistance of the device connected
to the output of the power supply.
And this follows Ohm's law:
current(in amps) = voltage(in volts) / resistance(in ohms)
In other words the adaptor will supply the device
with any amperage as required by the device, up
to the maximum value indicated on the label. Above
that, expect thermal breakdown.
JC
===
________________________________________________________
NetZero - We believe in a FREE Internet. Shouldn't you?
Get your FREE Internet Access and Email at
http://www.netzero.net/download/index.html
--
Live Long and Prosper, Happy trails...
** Bill Morrow ** :-)
WEB page http://thinkpads.com
Thinkpad User Community: http://thinkpads.com/enter.html
Compuserve Thinkpad(c) Forum Sysop
e-mail: bill_at_thinkpads.com, penzance_at_icanect.net
770Z-8AU, 760ED, 760CD, (5)701C, 560E, 755CE, 750C et al...
Including, but not limited to, Subject to prior sale, Your mileage will vary, Done on a
closed road with a professional driver AND Do not try this at home..
This archive was generated by hypermail 2.1.3 : Thu Jan 23 2003 - 09:55:11 EST