I don't know if anyone has had this happen, but today, I believe my AP74 failed in flight. It's powered from the avionics bus and the only way to remove power from it is to turn off the radio master switch. Unfortunately, when I do this, I loose radios, transponder, GPS, and my traffic alert system. During flight with my autopilot engaged in level cruise flight, I kept getting an EFIS message that said something like 'AP74 connection lost'. Don't know if that's the exact message, but it was something like that. I would acknowledge the message to make it go away and within about 15 seconds it looked like a white light inside the AP74 would flicker on for a second. I didn't see this at first, but after seeing it a couple times (the message kept coming back), I finally decided it could be arcing inside the AP74 case. I turned off the autopilot servo switch, but this had no effect. I shut everything down for a while and then powered back up. The AP74 stayed off (no lights) and I landed. I did hear audio 'pops' in my headset that went away when I turned the alert volume down to zero. I don't have the 'failover' alerts wired from the EFIS/EMS, but I'll be changing that. Tomorrow I'm going to remove the AP74 and have a look. When I do, I assume I'll have to reconfigure my system if I want to fly without the AP74. By the way, I have a FLTDEK 180, AP74, and two SV32 servos mounted in my RV-8. I'm wondering if I should have a separate power switch so I can isolate my AP74. Powering it through my avionics master doesn't allow this. This has been working fine in my airplane for 2 years, other than poor performance from my altitude servo being able to hold altitude in an acceptable way. That problem has been hashed over here on this forum, but no solution was found - yet.... in fact my airplane actually holds altitude better with the altitude servo turned off (I'm not trying to be funny - it's true). Please let me know if you think my AP74 is fried. There was no smoke, smell, or hot surfaces when this was happening. Maybe there's a little white light in there that I didn't know about......