OT: Will These Work?

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I have a wireless router and the supplied power adaptor has given up. The spec for the router is 12V DC 1A. I have two spare adaptors with the correct end for the router but one is 9V 1A and the other is switchable voltage but only 300mA. Before I go out and purchase a replacement would either of these be suitable? I presume the 9V one wont due to lack of voltage but will the lack of 700mA cause any problems if I use the switchable one?
Cheers
John
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You would be better asking this in uk.telecom.broadband, but no, neither will work, you will need to get your wallet out. If the PSU supplied with the router is rated 1A there's a reason for it!
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Woody

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Woody wrote:

Why not try the 9V one? Is running it at undervoltage going to give rise to any risk (fire, corrupt data, plague etc) - assuming of course "correct end" includes "correct polarity"? Isn't much modern electronics tolerant of low input voltage? And what's to little to lose (assuming the 9V adaptor is protected against overcurrent)?
--
R



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The chances are the router has other regulators within it. Whatever the regulator outputs they have to have an overhead on the input so that they stay in regulation - for many single chip units this is often 2.3V, so if 12V is the notional supply it suggests an internal supply of 9V in addition to the almost obligatory 5V. Run the unit from 9V and the 9V regulator will not work correctly and may stop the whole thing operating reliably.
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Woody

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Thanks for the explanation

But I still don't see why that militates against a "suck it and see approach", unless you agree with those who have warned of overheating. (I can only offer one data point: a Netgear router ran for a couple of weeks from a 9V PSU when its 12V failed, though I do not know how well the 9V was regulated.)
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R



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On Sun, 27 Sep 2009 18:24:24 +0100

Actually, that's damned worrying, 'cos 1A is a hell of a lot for a router, it's 240 watts!
Whereas I'd expect a router to draw about 75 watts, in which case a 300mA jobby might just do it. Try and fry?
R.
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On 27/09/09 20:42, TheOldFellow wrote:

12V x 1A = 12W

I'd say even that is out by a factor of 5 to 10.
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On Sun, 27 Sep 2009 21:12:51 +0100

Damn, yes, it's been a long day. Of course you're right. I think I'll go and have a beer....
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On Sun, 27 Sep 2009 20:42:23 +0100, TheOldFellow wrote:

How, exactly, do you work that out? The old PSU was rated at 12 volts, 1A. So that's 12 watts.

WHAT? My router (nothing special) draws 10 watts.
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Err
12V x 1A = ...

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geoff

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Some routers (inc in the Netgear range) have a built in print server. So the higher power rating of the adapter *may* be due to the need to drive the USB port(s) for attached printers.
Midge.

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Suck it and see - its unlikely to do any damage

Probably because it is what they used on the previous model ...
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geoff

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The 9V one probably won't work but would be worth trying. The 12V 300mA one might get fried.
Owain
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wrote:

Set the adjustable one to 12V and connect them in parallel.
Please let us know the outcome.
Bill
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The highest voltage one will supply all the power, unless it is dragged down so far as the lower voltage one. So not really worth the effort.
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Andrew Gabriel
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On Sun, 27 Sep 2009 18:20:50 +0100, John wrote:

That might work - the 12V power adaptor might be a simple dumb device (transformer, recitifer, capacitor and a fuse if you're lucky), with the 12V measured under 'no load' conditions; the first thing the router might do internally is run the input through a voltage regulator which produces a stable-but-lower voltage (although it would surprise me if it's all running on 5V internally but they still supply a 12V PSU; that's quite a drop).
cheers
Jules
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If you send me an email direct, stating what router it is for and the power plug configuration, I am more than willing to send you a power supply if I have one in my junk box. I know I have some 12V 1A ones
Kindest regards,
James
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Actually ... now you mention it , so have I
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geoff

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wrote:

I suspect not, or not properly, or you'll get over heating problems (plenty common enough in routers anyway IME).
A new power supply will be disproportionately expensive, especially if you have to pay delivery but try Google and EBAY anyway.
New routers are usually very cheap nowadays if yours is nothing very special.
Derek
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Er, no. An adjustable SMPS 3 to 12V, 1,200mA, lots of different interchangable plugs is/was under a tenner (7.75 IIRC) at ... Tescos. I've got quite a few of them running all sorts of things including my doorbell and my electronic door locks and they're fine.
As an aside I can't see how you would get overheating problems with undervolting electronics, motors maybe but electronics no.

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