[SATLUG] OT: Replacing a power adapter

Walt DuBose dubose at texas.net
Sat Feb 19 16:20:57 CST 2011

On 02/18/2011 09:25 PM, Geoff Edmonson wrote:
> On 02/18/2011 09:20 PM, Alan Lesmerises wrote:
>> A few days ago when they had those rolling black-outs, the power
>> adapter for my scanner apparently died. I don't know if that was the
>> cause or if it was coincidence, but it was dead nonetheless.
>> I found what appears to be a replacement at Goodwill, but it's not
>> quite an exact match. The old one was 12VDC/1.25A output, and the
>> replacement is 13VDC/1.3A.
>> I'm thinking that's probably not enough of a difference to matter, but
>> I wanted to get your (collective) opinion or if any of you have had
>> any similar experiences.
> I don't feel that 1v is enough difference to matter. It seems it's got
> enough current handling capability.
> What I -would- watch for, is that the center-pin of the female plug
> (coming from the power supply) is the proper polarity.

Many times the current rating is more important than the voltage.

If the wallwart is 12V @ 1.25A it can probably take up a 12V @ 1.5-1.7A.
However, if its needs to be 12V and you find one at 13.5V or 14V @ 1.7A, 
and your device only required 1.25A, then the output when you device is 
turned on could be 15-16V.

WallWarts ARE NOT voltage regulated and are regulated by the amount of 
current they can supply.

That said, if you don't have one of the $3 voltmeters from Harbor 
Freight, then get one and measure the voltage to insure that the 
WallWart isn't over 1.5V to 2V over you needed voltage without being 
plugged into you device.


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