Universal Laptop AC Adapters--Compatibility?

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If one of these universal adapter works with a laptop, i.e., has a tip that
fits, the laptops shows as being connected to AC when it is used, etc., does
that mean it is fully compatible? Or, could it be possible, even if it
works, that if one of the specs are wrong, that it could damage the computer
in some way?

Specifics in my case--I have a recently-purchased Fujitsu P7010D subnotebook
computer. I bought a Kensington model 33192 universal adapter to use with it
(and other notebooks of mine) while not at home, while leaving the original
AC adapter plugged in to use at home. This model of universal adapter is
very thin and light, which is nice to carry with one. It certainly seems to

In reading the specs on the Kensington Universal, and on the original
adapter, I see some differences, though, so I'm wondering if any of the
differences could be harmful in the long run, to use the Kensington with
this notebook. I will give details on all the specs----

The Kensington is a 70w adapter. I think that is no problem, although I
cannot find a wattage listing on the Fujitsu (original) adapter.

Voltage on the original is 16 volts. One of the listings on the Kensington
is 0-24 vdc, which I assume refers to the voltage. In other words, it can
handle different voltage settings, to handle notebooks that require
different voltages, as I think all such universal adapters do. I have seen
some (APC, for example) where you set the voltage on the universal
adapter--this Kensington has no such setting. I assume it automatically
determines what voltage is needed. If it does that correctly, I assume there
is no problem there either.

The Fujitsu adapter has the symbol for positive tip. I see no tip symbol on
the Kensington, no way to set the tip positive or negative, and the tips
only fit on one way. I assume it figures that out correctly though, as with
the wrong (positive or negative) tip, I don't think the adapter would work
at all.

I'm a little concerned about the amperage. The Fujitsu adapter lists input
at 100v 1.4 amps, output at 16 volts 3.75 amps. The Kensington adapter lists
input at 100-120v at 1.3 amps, output at 3.5 ADC. (I assume ADC refers to
the amperage.)

I know it is no problem if the amperage on an adapter is more than what is
needed (unlike the voltage, where the setting has to be the same), but it
could be a problem if the amperage is too low. In this case, both the input
and output voltages on the Kensington universal adapter are lower than those
listed on the original Fujitsu adapter, although by small amounts:

Input---Fujitsu, 1.4, Kensington 1.3

Output--Fujitsu 3.75, Kensington 3.5

Could these differences (or any of the others) cause a problem, even though
the computer seems to work fine with the Kensington adapter?

Re: Universal Laptop AC Adapters--Compatibility?

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I think you really ought to read its manual!

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Don't worry about it. Those are maxes. Of more concern to me would be
how on earth the thing determines the correct polarity and voltage to

I suppose it might supply AC and rely on the portable's diode
protection! If I were you I'd be breaking out the multimeter, just out
of curiousity.


Re: Universal Laptop AC Adapters--Compatibility?

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There are programming resistors and appropriate wiring in the
power-tip that's plugged into the end of the cable.  Disconnect it and
you'll see four pins.  Make sure you don't use any tip that fits, but
the tip that's exactly applicable to your laptop.

IIRC, the Kensington is rated at 60W, which is what you need.  An
extra 250mA isn't going to make much difference unless you hit the
maximum power load while charging a nearly dead battery, and then
it'll probably just slow the battery charging down by a bit.

Re: Universal Laptop AC Adapters--Compatibility?

William P. N. Smith <> wrote:
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Oh I see. It relies on you. Instead of a switch with settings, there
are the different sized and shaped tips. No sensory inputs involved.

I'm surprised the socket shapes are diagnostic enough on laptops! The
scheme sounds like an accident waiting to happen to me.


Re: Universal Laptop AC Adapters--Compatibility?

The socket shapes are not "diagnostic", and errors are possible.

It is conceiveable that you could use a tip that "fits" (perfectly) but
was wrong.

For example, the Targus adapters now support over five dozen tips.  Some
of those tips are mechanically identical (will fit perfectly) but are
configured to produce significantly different voltages for different

So if it says to use the "green #15A tip" for your model of laptop, you
MUST use that tip, even if the blue #17B tip also fits perfectly and
looks identical.  In fact, in such a situation, using the wrong tip
(that fits perfectly and looks identical) could indeed destroy the
laptop (or cell phone, PDA or whatever device you are powering ....
these are not just for laptops).

Peter T. Breuer wrote:

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Re: Universal Laptop AC Adapters--Compatibility?

It might not have enough power output to fully power the laptop under an
extreme high load, but even if that was the case, the risk of permanent
hardware damage will be near-zero.  Only significant over-voltage (more
than 5% to 10%) would be likely to cause damage.

Watts = volts * amps, so a 70 watt adapter putting out 16 volts is
CAPABLE of putting out up to 4.375 amps.  Note "up to" .... the
computer, not the power adapter, determines the current drawn.  However,
the computer can't draw more than the maximum that the adapter can
provide.  But even if the adapter falls short (even VERY short), you
would not expect to see actual damage, just transient device failure
(blue screens, lockups, etc.  ..... You COULD see data loss on the hard
drive, but probably nothing that, worst case, a repartition/reformat
would not fix.  PROBABLY.)

Normally, on universal adapters without manual voltage setting, the
voltage is set by the choice of "tip" at the end of the cable.

Note that since the universal adpater can presumably supply up to 4.375
amps, while the factory adapter could supply only up to 3.75 amps, you
are fine.  Again, the laptop, not the adapter, determines the current
actually supplied, the only requirement of the adapter in terms of
current is that it must be able to supply as much as the laptop asks
for.  In this case, the Universal adapter is capable of supplying MORE
than the factory adapter, so everything is cool.

[You list the Kensington adapter as having a capacity of "70 watts" and
a current capability of 3.5 amps.  3.5 amps at 16 volts is only 56
watts, so there is a conflict here, but in any case, in this situation
as you have described it, you should be fine, even if the OEM adapter
had a current rating of 3.75 amps while this universal adapter is 3.5
amps.  I would not worry about a shortfall this small, the notebook
likely draws FAR less than the maxiumum rating under all but extreme and
rare conditions.]

MS wrote:

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