I used a 9V power adapter on a 12V power device

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MechRocket

Joined Aug 20, 2005
2
Hi, I did something really stupid. On my portable LCD screen that is powered by a 12V power adapter, I plugged in a 9V power adapter and now it won't work anymore. Is there any way I can fix it? My dad said something about a fuse probably being blown or something and we might be able to fix it by replacing it with another fuse from Radio Shack.

Is he on the right track? If not, is there anything I can do?

Thanks so much.
 

pebe

Joined Oct 11, 2004
626
Originally posted by MechRocket@Aug 20 2005, 10:24 AM
Hi, I did something really stupid. On my portable LCD screen that is powered by a 12V power adapter, I plugged in a 9V power adapter and now it won't work anymore. Is there any way I can fix it? My dad said something about a fuse probably being blown or something and we might be able to fix it by replacing it with another fuse from Radio Shack.

Is he on the right track? If not, is there anything I can do?

Thanks so much.
[post=9755]Quoted post[/post]​
Plugging in an adapter with a lower voltage would not generally harm the unit. But if the polarity is reversed then it probably would cause damage and that may be what has happened.

It may just have blown a fuse.
 

thingmaker3

Joined May 16, 2005
5,084
To check polarity, you will need to use a voltmeter to measure both the 9Vdc and 12Vdc adapters. If the polarity of the 9Vdc supply is opposite of the 12Vdc supply, then you will probably need to replace the LCD screen. :(
 

CATV

Joined Apr 17, 2007
11
I have made this mistake and generally the device has a fuse to avoid damage when a reverse current is applied. If you are handy with PC boards, look for this open fuse (sometimes looks like a tiny resistor) and test to see if it is open. If so, replace it.
 

Salgat

Joined Dec 23, 2006
221
Just a quick question, why wouldn't a diode be used inside the LCD Screen to prevent a problem like this from happening? (from the engineering standpoint)
 

goodbyegti

Joined Apr 28, 2004
59
Maybe you used an unregulated PSU? These often devlop voltages far higher than the specified output voltage under low load. When the monitor is in standby it presents little load on the PSU. Monitors usually use switch mode PSUs which are regulated.
 
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