It's quite on-topic. I'm looking at a wall-wart that I got with my answering
machine back in '79.
I use a 9V wall-wart to provide input to a +15 volt supply, which is the
output of a regulator in the load, so it clearly pushes out a higher voltage
than what it says. It's well to keep in mind that the label suggests (but
doesn't guarantee) that the output is of a given voltage at a given current.
That may, in fact, be true, but I wouldn't bet on it. The majority of these
devices work in the +/- 10% realm, so I wouldn't expect close line or load
regulation.
Dick
----- Original Message -----
From: "Chris" <mythtech_at_mac.com>
To: "Classic Computer" <cctalk_at_classiccmp.org>
Sent: Friday, June 07, 2002 10:32 AM
Subject: [OT] measuring DC wall wart
> This is off topic, since the wall wart is only a few years old, but there
> are some great electrical people here, so I am asking because I know
> someone will know the answer.
>
> I have a wall wart to a modem. I got the modem and wart in a box of used
> stuff (ooh, some of which was more than 10 years old, so at least there
> is a reference to on-topicness).
>
> The modem failed to work from the day I got it. Today, someone that has
> the same modem asked if I had a power supply they could have. I planned
> to give them mine, since I have no real use for it.
>
> But before I mailed it to them, a voice went off in my head telling me to
> stick it on a meter first. It's label says it is a 9vDC, 400mA Pos-tip
> wart. But when I hook it up to a meter, I get 15v DC off it.
>
> That seems a little high, even for something under no load. Should I
> safely assume the wart is no good, and point the person elsewhere (Rat
> Shack sells a usuable unit for only about $14, so it isn't like the
> person has no other choice). Or is it normal for a 9v supply to put out
> 15 volts? Any that I have measured in the past have not been THAT far off
> (I was expecting to maybe get 10 or 12 volts, but not 15).
>
> If this thing has been pumping too much voltage, that might explain the
> dead modem I have (or the modem could have been used as a soccer ball,
> who knows, it was dead when I got it). I just don't want to send the
> person a bad supply, and have them fry their modem when they try to use
> it.
>
> -chris
> <http://www.mythtech.net>
>
>
Received on Fri Jun 07 2002 - 13:53:34 BST