18V adaptor putting aout 23V

[joelap]

Hey guys, I snagged an 18V DC adaptor from a local electronics store.  Problem is, when I measure it on my meter (black lead in the center, red lead on the exposed metal tip), it reads around 23.xx volts.  I know it is 18V as it is labeled as such... is this just a poor adaptor or am i measuring incorrectly?  To test, i plugged it into a pedal I built and measured the DC inside and again it read 23.xx volts.  Unfortunately I cant return it because I bought it center positive (only thing they had) so I reversed the wires to make it center negative like I needed.  Would this be OK to use and is this typical of adaptors?  I really dont want to have to put an 18V Zener in my pedals to regulate them down...

Joe

[slacker]

It's probably an unregulated adaptor and it will only put out 18 volts at a specified current, this is normally written on the adaptor. If your pedal is pulling less current than this the voltage will be higher than 18 volts.
It shouldn't cause any problems so long as the components in your pedal can handle the voltage.

[joelap]

Aha!  Thanks for that tidbit!

[CGDARK]

If it is putting out 23V or more is because is a not regulated one. This may introduce noise in a circuit, so you must filter it very well or you can add a voltage regulator (7818,78L18,etc.) and a filter cap (rated at 35V or more) and you are done (no hum, no noise and a well filtered power supply). Good luck.

CG