# Voltage and Amperage question



## williamc (Jul 19, 2004)

I have a KVM that requires 9V DC 600mA
I have a power adaptor that is 9V 1A

Will this power adaptor work with the KVM? Thanks.

William


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## McTimson (Aug 16, 2002)

As long as the plug fits, then yes, it should work fine. The adapter will only draw as much current as the KVM needs, 600mA, which is less than the 1A it can supply.


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## gotrootdude (Feb 19, 2003)

Another thing to know is that you can generally use a lesser voltage for running this type of equipment, as there's a tolerance built in. I wouldn't be surprised is a 7V adaptor didn't work fine.


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## Noyb (May 25, 2005)

Most KVMs are powered from the Keyboard's PS2 connections for each KVM input.
Are you sure yours isn't powered this way ??


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## wacor (Feb 22, 2005)

not familiar with voltage variances on DC but the motors I use which are AC they always say the voltage needs to be within 10%


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## gotrootdude (Feb 19, 2003)

Well, in this case, most small KVM's either use the voltage off the USB or the voltage from the PS2. That's 5V. So chances are good that the KVM only needs 5V to operate. But electronics being the way they are, the manufacturer may have decided to add an additional power adaptor instead of relying on the PC's power output since not all PC's provide stable current through the USB or PS2 ports. And, it's probable that the 9V adaptor could be purchased by the manufacturer at a lower cost than a 5V adaptor would cost, in which case it would be easy to add a current limiter to lower it to a operational voltage. So, you may find that the device is able to operate on as low as a 5V adaptor, as long as the minimal amperage is met. :up: Of course, it's only speculation until it's tried, and your not going to damage anything by trying a lower voltage, but you might fry it trying a higher voltage. 

AC and DC are two very different animals.


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## JohnWill (Oct 19, 2002)

Since 9V is a very common P/S module, there's no real reason to try to run this on a lower voltage unit. However, you should note that some of the cheap "wall wart" supplies are not regulated, and if they're lightly loaded, the output voltage could be significantly higher than the rating.


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## Jedi_Master (Mar 13, 2002)

Howdy folks...

williamc...

Should work, as long as the correct polarity is observed between the adapter and KVM switch (remember DC has a polarity + & - ), the symbol should look like this on the adapter and KVM, if it's not there may have to do some reasearch on the KVM and adapter (the adapter you can check with a volt meter)...

For Positive center...










For Negative center...










If you plug in one that is different then you may blow either/both the KVM and adapter...


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## JohnWill (Oct 19, 2002)

FWIW, the center pin being the positive side is much more common, though sadly not universal.


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## williamc (Jul 19, 2004)

Thank you for the detailed information. The plug did work as you all suggested. The reason I needed 9V was because the PS2 mouse is optical. It would act sporatic when used. Belkin recommened connecting a power adaptor to the KVM. This fixed the problem. Thanks again!

William


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## JohnWill (Oct 19, 2002)

Glad it all worked out.

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