Very careful matching power supplies here too! 24 volts is less common,so more care is needed in matching.Whats the current draw?. Maybe the 12 volts left the pedal looking for more,so it drew more current than was safe. Maybe the polarity issue, as others pointed out,is the factor, if there is a protective diode, as 20cent said.Contact the pedal maker and explain what happened.
Is it a pedal that MF sells? If not, you are on your own. If it is...well,maybe some recourse.
Getting a substitute power supply in this day and age from non-oem vendors, with the ga-zillion different pedal architectures out there can be risky.You must match exactly the needs of the pedal to what you are getting, if you are buying from non-oem vendor.Maybe if you got a 24 volt supply,it would have caught fire!
In the end,with all those choice high-end expensive pedals out there,a nice stable, quality power supply is your friend.Treat your high end pedals.Cheapo wall warts are OK.but they fry sometimes too easily.
I’ve always been pretty happy with the prices and service with MF but once in a while I get into a real head scratcher situation with their phone reps. I bought an amp about three weeks ago, level one mint condition $439.99. Few days later, they have the same one in the same condition for $294 and change. I called him up to see if they would price match that, and they said sure. They said they would send me a credit of $145 and change back to PayPal. It never showed up. In the meantime, I decided the amp was not usable, because when you kicked on the overdrive, the volume jump was alarming, just not right. I called in about it, they agreed to let me return it for a refund. Few days later, I get a notification that I’ve gotten a refund of $294. That’s obviously because they think they’ve already given me $145. I called, and the guy kept repeating himself over and over, explaining why it was only $294. I said I understand the math, but I never got the $145, so you still owe me money. He couldn’t understand what I was saying, thought I was the one that was having trouble. I actually ended up filing a claim with PayPal, they are still going through it, I’m sure it will be settled appropriately.