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voltage AC/DC question

C

cmdavid

Diamond Member
I've got a question about buying an AC Adaptor for a modem i have. Here are the specifications the manual says.

AC/DC: 120V/9V

The supplied adapter has the following output specifications:
 9VDC/1A unregulated output voltage
 Maximum 860 mVeff ripple voltage
 Maximum 1A output current
 Limited power source (according to IEC/EN 60950,
subclause 2.11 and UL1950).

Now i found an adaptor laying around my house that says this on it:
Input:120VAC 60Hz 30W
Output: 12VDC 1.2A

I can see that this adaptor is 12V instead of 9V and 1.2A instead of a max of 1A.. but will it hurt my modem? If so, where is the best place to buy AC Adaptor's like the one ive described, RadioShack doesnt have any they say. Thanks in advance..

-Chris
 
Yes.

If it is 9v @ 1A, you MUST use a 9v adapter. 12v will most likely kill it, if not instantly.

The amperage doesen't matter, as long as it is 1 amp(1000mA) or more @ 9v.
 
Originally posted by: cmdavid
Thanks Eli, but does the AC part matter, the 120V?
Click to expand...
No.

That's your standard home line voltage. It will be the same for all wall-warts, unless you come across one from another country.
 
I found an adaptor that says on it
DC Output: +5.0V ==== 2.0A

It's for a D-Link Switch...

do you know if that will work?

the specs on the switch are 7.5VDC/1A
 
Originally posted by: cmdavid
I found an adaptor that says on it
DC Output: +5.0V ==== 2.0A

It's for a D-Link Switch...

do you know if that will work?

the specs on the switch are 7.5VDC/1A
Click to expand...
No...... 😛

If the modem requires 9v @ 1A, you have to give it 9v @ 1amp(or more, the device will only pull as much amperage as it needs).

If it said 9v ==== 2.0A, it would be OK.
 
Originally posted by: Eli
Originally posted by: cmdavid
I found an adaptor that says on it
DC Output: +5.0V ==== 2.0A

It's for a D-Link Switch...

do you know if that will work?

the specs on the switch are 7.5VDC/1A
Click to expand...
No...... 😛

If the modem requires 9v @ 1A, you have to give it 9v @ 1amp(or more, the device will only pull as much amperage as it needs).

If it said 9v ==== 2.0A, it would be OK.
Click to expand...
ok.. sorry about that last question, only reason i asked was because it had that litte plus sign... and because it is a 5V adaptor and it came with a 7.5V switch... thanks again eli.... sorry for my nooobism...

 
Originally posted by: cmdavid
Originally posted by: Eli
Originally posted by: cmdavid
I found an adaptor that says on it
DC Output: +5.0V ==== 2.0A

It's for a D-Link Switch...

do you know if that will work?

the specs on the switch are 7.5VDC/1A
Click to expand...
No...... 😛

If the modem requires 9v @ 1A, you have to give it 9v @ 1amp(or more, the device will only pull as much amperage as it needs).

If it said 9v ==== 2.0A, it would be OK.
Click to expand...
ok.. sorry about that last question, only reason i asked was because it had that litte plus sign... and because it is a 5V adaptor and it came with a 7.5V switch... thanks again eli.... sorry for my nooobism...
Click to expand...
It's fine. Gotta start somewhere. 😉

I'm surprised nobody else has chimed in.. :Q This thread is invisable. 😉

*flails arms about* IN HEEREEE PEOPLE!
 
Depending on the device, you often have a bit of voltage leaway when replacing a power supply. One of the first things most devices will do is pass the unregulated input voltage through one or more onboard voltage regulators to provide the various working voltages to the internal components. Supplying a higher input voltage will put more stress on the regulators (they'll dissipate more heat) but things will generally still work as long as the device doesn't overheat. I'm currently using a 20V power supply with a small network computer who's original power supply was rated at 18V.

Powering a 9V device with a 12V power supply is probably a little excessive. 25%. But you should be able to get away with 10-15% overvoltage as long as overheating isn't a problem.

The thing that's critical is that your power supply be able to supply sufficient current.
 
You can *probably* power the 9V device from the 12V supply. The voltage regulater inside will get hotter, but it will probably work.

The other thing you have to worry about is polarity. The plug has a center hole and an outside sleeve. It will be either "center positive" or "center negative" and that will be illustrated on the printing on the power brick. You have to replace the adapter with like polarity.

(Unless the output is AC, in which case the device likely has a bridge rectifier right at the input and will accept either AC or either DC polarity. But that, too, is a "probably.")
 
Originally posted by: Eli
Originally posted by: cmdavid
I found an adaptor that says on it
DC Output: +5.0V ==== 2.0A

It's for a D-Link Switch...

do you know if that will work?

the specs on the switch are 7.5VDC/1A
Click to expand...
No...... 😛

If the modem requires 9v @ 1A, you have to give it 9v @ 1amp(or more, the device will only pull as much amperage as it needs).

If it said 9v ==== 2.0A, it would be OK.
Click to expand...

Actually, there are some (really cheap) wall warts that will supply their rated voltage only when the device connected draws the rated current. Thus, a 9V @ 2.0A wall wart has the possibility of supplying more voltage than 9V if you're only pulling 1A from it instead of 2A.

JW
 
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