| Author |
Message |
Guest
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 Posted:
Wed Dec 29, 2004 8:09 pm Post subject:
Modem power supply |
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Hello,
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without damaging
the modem?
Thank you in advance. |
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Paul Worsley
Guest
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| Posted:
Wed Dec 29, 2004 10:20 pm Post subject:
Re: Modem power supply |
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<none@no.invalid> wrote in message
news:Xns95CE67424BFE0nonenojinvalid@netnews.worldnet.att.net...
| Quote: | Hello,
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without damaging
the modem?
Thank you in advance.
|
Highly unlikely that the modem takes anything like 1000mA
Main thing to watch out for is polarity of the plug, and that the PSU is DC
and not AC output
Modem probably regulates down to 5V
Modem "should" be protected against polarity and slight overvoltage.
Paul
real is pjw at ntstelcom#co#uk
Modems for Landline SMS
Landline SMS with a PC www.z-text.com |
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Guest
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| Posted:
Wed Dec 29, 2004 11:27 pm Post subject:
Re: Modem power supply |
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"Paul Worsley" <pjw@WRONGntstelecom.co.uk> wrote in
news:41d2e6f0$0$12227$cc9e4d1f@news.dial.pipex.com:
| Quote: | none@no.invalid> wrote in message
news:Xns95CE67424BFE0nonenojinvalid@netnews.worldnet.att.net
...
Hello,
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without
damaging the modem?
Thank you in advance.
Highly unlikely that the modem takes anything like 1000mA
Main thing to watch out for is polarity of the plug, and
that the PSU is DC and not AC output
Modem probably regulates down to 5V
Modem "should" be protected against polarity and slight
overvoltage.
Paul
real is pjw at ntstelcom#co#uk
Modems for Landline SMS
Landline SMS with a PC www.z-text.com
Thank you for the explanation. |
I wasn't clear earlier. The "modem requires" should have been a
la the modems's old (now dead) power supply had "9 V 1000 mA"
written on it.
Again, thanks. |
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Floyd L. Davidson
Guest
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| Posted:
Thu Dec 30, 2004 6:36 am Post subject:
Re: Modem power supply |
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none@no.invalid wrote:
| Quote: | "Paul Worsley" <pjw@WRONGntstelecom.co.uk> wrote:
none@no.invalid> wrote:
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without
damaging the modem?
Thank you in advance.
Highly unlikely that the modem takes anything like 1000mA
|
Perhaps uncommon, but not at all "unlikely", because there
are *many* modems that do.
| Quote: | Main thing to watch out for is polarity of the plug, and
that the PSU is DC and not AC output
|
You haven't specified if that is an AC or a DC power supply
requirement. If in fact the modem says "9V 1.0A AC", then it
will also work with a DC power supply, and in fact the actual
voltage may not make much difference as long as it is about 9
volts or a little higher (it could even be a little lower if the
current rating of the supply is significantly higher).
| Quote: | Modem probably regulates down to 5V
|
It almost certainly will have an onboard 5V bus derived from the
main supply. But it will also have other voltages too,
including one that is probably going to be very close to the
supply voltage (or some multiple of it if the supply is 6 V, for
example).
| Quote: | Modem "should" be protected against polarity and slight
overvoltage.
|
Don't bet on either though.
| Quote: | I wasn't clear earlier. The "modem requires" should have been a
la the modems's old (now dead) power supply had "9 V 1000 mA"
written on it.
|
Does it indicate if it is AC or DC? As noted, if it says AC you
can feed it either AC or DC.
A supply with too low a current rating will not damage the
modem, but there are other negative effects very likely. The
current rating is for peak current, so while the modem will
rarely draw the maximum, when it does the effect of an under
rated power supply will be a drop in voltage when the peak
current is drawn. That might cause your modem to simply drop
calls, or to become totally wedged, or perhaps only drop a
character or two (which you won't even notice). No hardware
damage to the _modem_ though.
But overall the _power_ _supply_ is going to be overloaded, and
is very likely to fail after a relatively short period of time.
Given that the original power supply has already failed, the
chances are not good for one rated at 80% the power of the
original!
It appears that what you should be looking for is a power supply
with *more* than 1000 mA current rating rather than lower. Don't
go too high, because the voltage is going to actually be higher
when less than the rated current is drawn, plus the heat
dissipated by linear voltage regulators goes up as the input
voltage goes up. Hence I would not recommend a 12V 1.2A supply,
though it would probably work. Likewise a 9V 2.0A supply would
almost certainly work, but might be pushing it too.
Look for a 9 V supply rated between 1.2 and 1.6A, and you'll
never need to replace it again.
(If by some chance this is for a USR Courier modem, you can use
anything up to a 22 V power supply as long as it has the current
rating.)
--
Floyd L. Davidson <http://web.newsguy.com/floyd_davidson>
Ukpeagvik (Barrow, Alaska) floyd@barrow.com |
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Guest
|
| Posted:
Thu Dec 30, 2004 8:03 am Post subject:
Re: Modem power supply |
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floyd@barrow.com (Floyd L. Davidson) wrote in
news:87652ktvms.fld@barrow.com:
| Quote: | none@no.invalid wrote:
"Paul Worsley" <pjw@WRONGntstelecom.co.uk> wrote:
none@no.invalid> wrote:
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without
damaging the modem?
Thank you in advance.
Highly unlikely that the modem takes anything like 1000mA
Perhaps uncommon, but not at all "unlikely", because there
are *many* modems that do.
Main thing to watch out for is polarity of the plug, and
that the PSU is DC and not AC output
You haven't specified if that is an AC or a DC power supply
requirement. If in fact the modem says "9V 1.0A AC", then
it will also work with a DC power supply, and in fact the
actual voltage may not make much difference as long as it
is about 9 volts or a little higher (it could even be a
little lower if the current rating of the supply is
significantly higher).
Modem probably regulates down to 5V
It almost certainly will have an onboard 5V bus derived
from the main supply. But it will also have other voltages
too, including one that is probably going to be very close
to the supply voltage (or some multiple of it if the supply
is 6 V, for example).
Modem "should" be protected against polarity and slight
overvoltage.
Don't bet on either though.
I wasn't clear earlier. The "modem requires" should have
been a la the modems's old (now dead) power supply had "9 V
1000 mA" written on it.
Does it indicate if it is AC or DC? As noted, if it says
AC you can feed it either AC or DC.
A supply with too low a current rating will not damage the
modem, but there are other negative effects very likely.
The current rating is for peak current, so while the modem
will rarely draw the maximum, when it does the effect of an
under rated power supply will be a drop in voltage when the
peak current is drawn. That might cause your modem to
simply drop calls, or to become totally wedged, or perhaps
only drop a character or two (which you won't even notice).
No hardware damage to the _modem_ though.
But overall the _power_ _supply_ is going to be overloaded,
and is very likely to fail after a relatively short period
of time. Given that the original power supply has already
failed, the chances are not good for one rated at 80% the
power of the original!
It appears that what you should be looking for is a power
supply with *more* than 1000 mA current rating rather than
lower. Don't go too high, because the voltage is going to
actually be higher when less than the rated current is
drawn, plus the heat dissipated by linear voltage
regulators goes up as the input voltage goes up. Hence I
would not recommend a 12V 1.2A supply, though it would
probably work. Likewise a 9V 2.0A supply would almost
certainly work, but might be pushing it too.
Look for a 9 V supply rated between 1.2 and 1.6A, and
you'll never need to replace it again.
(If by some chance this is for a USR Courier modem, you can
use anything up to a 22 V power supply as long as it has
the current rating.)
|
OK! - Now some home work / study to do. :)
FWIW: Both warts are 9V AC; the modem is USR Faxmodem 56K.
Thank you very much for the additional info. |
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Jeroni Paul
Guest
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| Posted:
Sat Jan 01, 2005 11:42 pm Post subject:
Re: Modem power supply |
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Floyd L. Davidson expuso:
| Quote: | But overall the _power_ _supply_ is going to be overloaded, and
is very likely to fail after a relatively short period of time.
Given that the original power supply has already failed, the
chances are not good for one rated at 80% the power of the
original!
|
I guess just a bad solder joint or a dry capacitor.
Best and safest would be to crack open the original PS and repair it. |
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Franc Zabkar
Guest
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| Posted:
Sun Jan 02, 2005 1:22 am Post subject:
Re: Modem power supply |
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On Wed, 29 Dec 2004 15:09:12 GMT, none@no.invalid put finger to
keyboard and composed:
| Quote: | A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without damaging
the modem?
|
All other things being equal (polarity, AC/DC) a lower wattage PS
should not damage your modem.
This old post suggests that your USR modem *may* be able to get by
with an adapter of only half the rated wattage:
http://groups-beta.google.com/group/comp.dcom.modems/messages/3ce1e2217b74f95d,5e8f21048b6cb4cf,13b317f83ac35f2d,9cfcd242c1039ba9,fb8d29d17f05ead5,456d02d29c791c68,d3aeef761827ced8,d64dbbd1e18835c7,41f4a273793bcbf7,ec4ba26621a5d740?thread_id=a1a282cc59e38952&mode=thread&noheader=1&q=usr+voltage+group:comp.dcom.modems+author:Zabkar#doc_9cfcd242c1039ba9
Notice that the international version is rated at 9VAC 533mA while the
US version is 9VAC 1000mA.
- Franc Zabkar
--
Please remove one 's' from my address when replying by email. |
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Guest
|
| Posted:
Sun Jan 02, 2005 3:28 am Post subject:
Re: Modem power supply |
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Franc Zabkar <fzabkar@optussnet.com.au> wrote in
news:671et0to9l2i4llfj4mvl1pr1pv5rot3ni@4ax.com:
| Quote: | On Wed, 29 Dec 2004 15:09:12 GMT, none@no.invalid put
finger to keyboard and composed:
A modem requires 9 V 1000 mA power supply.
Is it possible to use 9 V 800 mA power supply without
damaging the modem?
All other things being equal (polarity, AC/DC) a lower
wattage PS should not damage your modem.
This old post suggests that your USR modem *may* be able to
get by with an adapter of only half the rated wattage:
http://groups-beta.google.com/group/comp.dcom.modems/message
s/3ce1e2217b74f95d,5e8f21048b6cb4cf,13b317f83ac35f2d,9cfcd24
2c1039ba9,fb8d29d17f05ead5,456d02d29c791c68,d3aeef761827ced8
,d64dbbd1e18835c7,41f4a273793bcbf7,ec4ba26621a5d740?thread_i
d=a1a282cc59e38952&mode=thread&noheader=1&q=usr+voltage+grou
p:comp.dcom.modems+author:Zabkar#doc_9cfcd242c1039ba9
Notice that the international version is rated at 9VAC
533mA while the US version is 9VAC 1000mA.
- Franc Zabkar
|
Thanks Frac.
(learnin' never ends ... ;) |
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Guest
|
| Posted:
Sun Jan 02, 2005 3:32 am Post subject:
Re: Modem power supply |
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"Jeroni Paul" <JERONI.PAUL@terra.es> wrote in
news:33o99mF430rlqU1@individual.net:
| Quote: | Floyd L. Davidson expuso:
But overall the _power_ _supply_ is going to be
overloaded, and is very likely to fail after a relatively
short period of time. Given that the original power supply
has already failed, the chances are not good for one rated
at 80% the power of the original!
I guess just a bad solder joint or a dry capacitor.
Best and safest would be to crack open the original PS and
repair it.
|
Given my "skills" ... WTH, it's dead, anyway. ;)
I'll try. Thanks for the tip. |
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Jeroni Paul
Guest
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| Posted:
Sun Jan 02, 2005 4:45 am Post subject:
Re: Modem power supply |
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none@no.invalid expuso:
| Quote: | Given my "skills" ... WTH, it's dead, anyway. ;)
I'll try. Thanks for the tip.
|
Also check the cable. It is the most stressed part and very likely to break.
In an electronics store you will find very cheap replacement parts for
everything, all you need is a soldering iron. Given that you mention it
outputs AC, the adapter is just a transformer, so that problem is very
likely a connection, cable or plug.. |
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