wall power supply reading higher voltage than listed...

[chemman]

12V DC 800ma wall adapter reading - 17.5V???

its a class 2 transformer - is this a normal deviation from listed voltage?  this was tested with no load.

[The Tone God]

Its probably unregulated. Stick a load on it and it will come down.

Andrew

[gez]

You should be able to find out what the variation is in your neck of the woods (power companies often produce figures for what they guarantee).  In the UK there's a plus or minus ten percent deviation.  The AC coming out of the wall sockets in our flat is close to the max (I routinely measure around 252V).

As Andrew mentioned, with a load it'll probably come down a little.

[chemman]

yeah, it dropped a few volts, seems fine.  but i'll need an AC adapter.

[R.G.]

This question comes up with each new batch of newbies.

Unregulated wall transformers are printed with their guaranteed minimum output voltage at the guaranteed maximum load.

So an adapter that makes 12Vdc at 200ma only makes 12Vdc when it is loaded with exactly 200ma. What they don't tell you is that to get there they had to use a lot of fine wire on the wall transformer and the resistances inside that transformer make the output voltage sag at full load. So you can expect that an unregulated wall transformer will be at least 10%, maybe 15-20% high on voltage when lightly loaded.

The moral of the story is - don't trust a cheap wall wart until you measure it under light and heavy loads and determine if it's regulated or not. If it's not, it can kill your pedals. Some commercial pedals use 10V rated electrolytic caps, or have chips in them that die if they're fed more than 10V.

[chemman]

Thanks for all the info.
I have recently obtained a variable power supply to fine tune the voltage.

Thanks again,

chemman