I have a problem with my CP-251. When I plug in the power adaptor, the LED in the LFO section no longer lights up and the controller does not appear to function. Does anyone have any suggestions why it should suddenly not work or power up?
Are you sure you plugged it in to the correct power adapter? If not, you might need a new unit.
Well, I used a +9v power adaptor that had the same polarity as the CP-251 and 200mA. I believed that to be the correct specification. Could the adaptor damage the CP-251?
If you use an adapter with the wrong polarity or too high of a current output then yes, damage can occur. However, I don’t see a problem with your setup. I don’t know why the 251 isn’t working in your case… 
I guess I’ll have to send it in to get the unit checked. Thanks for your replies. It’s appreciated.
You are most welcome. Good luck! 
Too LOW a current output can do damage. There is no such thing as too HIGH. The device will only draw what it needs regardless of what is available.
Have you metered the wall wart to see if there is any output? Can you try a different one?
What was else was the adapter used for ? does it still work on that or did you buy it just for the CP 251 ?
I’ve had wall warts go bad on occasion, either the plug that goes into the device or the transformer section. I had one for the Fooger go up a few years ago, the cable going into the connector developed a break in the wire some how, it was a simple cut the bad on off and solder a new one on .
As Just me stated a higher mh rating is not going to hurt anything, think of it as when you plug a 7watt night light into a 15amp circuit the bulb dose not blow up . I think Voltor may have meant higher voltage, that could be a problem. If you used the wrong polarity or a wall wart that outputs AC rather than DC, that could be a problem. If you have another wall wart compatible give it a try, if not your local Radio Shack may have a compatible one, otherwise contact Moog about buying one. Sure there may be a chance something fried, but good chance it did not.
Indeed, too much VOLTAGE, not current, will cause damage, as will too low CURRENT. 