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Question - any help appreciated

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hukkfinn

I have a component that takes a wall wart. I've lost the wall wart. I'm trying to figure out what will happen if I try a replacement that is DC when the unit may require AC.

The back of the component says "9V - AC" next to the input hole. It also says 1 amp, 5 watts.

I am finding many wall warts with these specs, but they are ALL converting AC to DC. If I try one that provides DC, and my unit wants AC, will it hurt the unit?

Thanks for any help-
Hukk

Follow Ups:

RE: Question - any help appreciated - Drew Eckhardt 19:14:10 08/29/07 (0)
9VAC actually varies between -12.7V and +12.7V.
Devices could depend on this by using a pair of half-wave rectifiers to produce a bipolar supply at something beyond +/- 9VDC; perhaps +/- 11V (depending on capacitor size and load) which gives enough headroom to use 3-terminal regulators for a solid supply. Most op-amps and push-pull audio circuits require split +/- supplies, and most devices get there with separate recitifers + filters instead of a virtual ground device.
9VDC could be AC with a half or full-wave rectifire producing a wave form with no negative component to produce the negative power supply; or a filtered 9VDC with no headroom for regulators.
You want to use a real 9VAC supply.

Edits: 08/29/07
RE: Question - any help appreciated - budm 12:27:54 08/27/07 (1)
What kind of the unit that you have? Some equipment needs to have AC input because it may be using half-wave rectifier circuits to provide the B+ and B- to power the circuit, without knowing what is really inside the box, I would suggest to get the wallwart from place like www.jameco.com P/N 102234 (2.1 X 5.5mm plug), 157041 (2.5 x 5.5mm plug.
If the unit has a bridge rectifier inside then it is true that you can connect the DC power supply to it without worrying about the polarity because the bridge will automatically take care of the polarity inside the unit.
- Kind of equipment - it's an Emu "Proformance" piano module - hukkfinn 08:21:32 08/29/07 (0)
  ... which makes the sound of a real piano when you hook up a keyboard to it via MIDI.
  
  I wish I knew anything about the internals of it, but I don't.
  
  Hukk
RE: Question - any help appreciated - Tweekeng 13:16:00 08/26/07 (2)
You should be ok using a 9V DC adapter (or even a 12VDC for that matter...
The AC is rectified (converted to DC) inside the unit anyway.
Sending DC will not be a problem as it will pass right through the rectifiers.
You do not even have to worry about polarity.

Edits: 08/26/07
- "You do not even have to worry about polarity." -- Really? - hukkfinn 08:45:07 08/27/07 (1)
  I was told to be especially, especially careful about ensuring that polarity is correct. Otherwise "meltdown" could occur.
  
  Sometimes people on here poke fun at newbies (which I definitely am when it comes to electronics), or give wrong advice as a bit of "hazing" -- just want to be sure this is not the case here since we are talking about something that could be dangerous to my family.
  
  Thanks,
  Hukk
  - How would you determine the polarity if an AC voltage? - Tweekeng 16:09:27 08/27/07 (0)
    Answer, you can't since an AC voltage is constantly changing polarity.
    No matter what way you hook DC up to the AC input the DC will be "routed" through the diodes and the unit will not know the difference.
    - AC/DC: What's the Difference? (Open in New Window)
    Edits: 08/27/07

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