From: John Woodgate
Subject: Re: Doubling wallwart power rating
Date: Mon, 7 Oct 2002 18:46:53 +0100
Organization: JMWA Electronics Consultancy
Reply-To: John Woodgate
NNTP-Posting-Date: Mon, 7 Oct 2002 18:24:06 +0000 (UTC)
X-Newsreader: Turnpike (32) Version 4.01 <5Z8C9wtxbnpWyFnyfFzqmVF739>
I read in sci.electronics.design that Phil Allison
wrote (in ) about 'Doubling
wallwart power rating', on Tue, 8 Oct 2002:
> ** John is speaking off the top of his head again. How many wall
>warts has he measured I wonder - less than me for sure.
Since you don't say how many you have measured, your statement is not
worth much. I've measured about 100.
> The last one I saw was rated at 12 volts and 500mA DC. It drew
>the same primary rms current with both full load and no load.
How did you measure it, exactly? Did you disconnect the rectifier, so as
to measure the *transformer's* no-load current? Did you use a true
r.m.s. meter, because the magnetizing current is very peaky? If that
transformer drew around 1 A (12 V x 500 mA x 1.6) on no-load, there was
something seriously wrong with it.
Remember our discussion about mains leads? When you gave me ALL the
facts about your tests, we agreed.
> You have to do tests to know - theory will not tell you.
Ah, well, that depends on whether you know how to apply the theory, of
Regards, John Woodgate, OOO - Own Opinions Only. http://www.jmwa.demon.co.uk
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