9V Plug top power supply measuring 13.5 Volts!!!

[Control Freq]

Hi,

Is this normal?
I have a plug top power supply, for UK. The sticker shows:
AC/DC Adaptor
Input 230V ~ 50Hz 11.2W
Output 9v 500mA 4.5VA

I have just measured the voltage at 13.5 volts (DC).

I guess I have bought a non-standard item!!

Anyone else experience this sort of thing before?


Regards

 

[Tim]

Try loading the output. It should drop the the 9 volts when loaded down.

- Tim -


In article <d0f8caf8-f342-4bec-adea-566521fd7558
@h2g2000yqj.googlegroups.com>, nick@nhthomas.freeserve.co.uk says...

Hi,

Is this normal?
I have a plug top power supply, for UK. The sticker shows:
AC/DC Adaptor
Input 230V ~ 50Hz 11.2W
Output 9v 500mA 4.5VA

I have just measured the voltage at 13.5 volts (DC).

I guess I have bought a non-standard item!!

Anyone else experience this sort of thing before?


Regards

 

[Rich Webb]

On Wed, 10 Feb 2010 06:44:25 -0800 (PST), Control Freq
<nick@nhthomas.freeserve.co.uk> wrote:

Hi,

Is this normal?
I have a plug top power supply, for UK. The sticker shows:
AC/DC Adaptor
Input 230V ~ 50Hz 11.2W
Output 9v 500mA 4.5VA

I have just measured the voltage at 13.5 volts (DC).

I guess I have bought a non-standard item!!

Anyone else experience this sort of thing before?

For devices that have their own internal regulation and that don't need
a tightly regulated supply (e.g., one that can run from a battery), this
kind of supply is simple and cheap. Think of it as a 13.5 VDC "pure"
supply in series with a source impedance of about 9 ohms. When it is
supplying a 500 mA load, that internal resistance will drop about 4.5 V,
so at the terminals you'll see the expected 9 VDC.

--
Rich Webb Norfolk, VA

 

[Dave Plowman (News)]

In article
<d0f8caf8-f342-4bec-adea-566521fd7558@h2g2000yqj.googlegroups.com>,
Control Freq <nick@nhthomas.freeserve.co.uk> wrote:

Is this normal?
I have a plug top power supply, for UK. The sticker shows:
AC/DC Adaptor
Input 230V ~ 50Hz 11.2W
Output 9v 500mA 4.5VA

I have just measured the voltage at 13.5 volts (DC).

I guess I have bought a non-standard item!!

Anyone else experience this sort of thing before?

Pretty well every power supply will read high if measured with no load.
Even a regulated type has a small internal parasitic load to allow the
regulator to work correctly.

What you've observed is perfectly normal for a basic non-regulated supply.
With a load drawing the quoted 500mA it should drop to 9 volts. Or
thereabouts.

--
*Can atheists get insurance for acts of God? *

Dave Plowman dave@davenoise.co.uk London SW
To e-mail, change noise into sound.

 

[bw]

"Control Freq" <nick@nhthomas.freeserve.co.uk> wrote in message
news:d0f8caf8-f342-4bec-adea-566521fd7558@h2g2000yqj.googlegroups.com...

Hi,

Is this normal?
I have a plug top power supply, for UK. The sticker shows:
AC/DC Adaptor
Input 230V ~ 50Hz 11.2W
Output 9v 500mA 4.5VA

I have just measured the voltage at 13.5 volts (DC).

I guess I have bought a non-standard item!!

Anyone else experience this sort of thing before?

That's normal. Note the rating is for 500 milliamps. Put a 500 mA load on
the output and you will see 9 volts.