The entire system other than the AP74 upgraded normally. This is the only device I have that must be upgraded over the DASB instead of with its own serial port. These two have to be related. I was however able to finally get a full firmware backup and upgrade with no errors. When it works, it works great.
So you were able to bring it all back to 5.1.1, then up to 5.2, including the AP-74...cool!
When I first intalled the servos and AP-74, I remember holding my breath as the update progressed, waiting for the program to see and ID them, and then upgrade them. Its been a while, and I can't remember if it did the servos first or the AP-74 first during the upgrade. I'm just thinking this through and scratchin' my head, and wondering (as you mentioned earlier) if the servos not yet being in your network is creating, or has something to do with, this issue.
Since the AP-74 has functions besides turning the AP on or off (i.e., moving the heading/altitude bugs and setting the altimeter with the value knob) it seems that it could be OK without the servos in the net. Then again, it does have the AP on-off and mode buttons...have you tried pushing that AP button or mode buttons to see what happens (if so, did it give a DSAB warning, like "no servos found"?)
And then there's the HS-34/AP-74 combo...they have some crossover functions (I believe...like those bug and altimeter settings), so maybe the combo of the 74/34 needs the servos in the net to prevent confusion between those devices. Just dunno. (Maybe if it was an AP-76...
)
Or maybe it's just the cold...but that doesn't seem to be a universal symptom in the field. I haven't upgraded to 5.2, and don't have cold issues, so could it be a 5.2 bug? (Don't know if Greg A is at 5.2, or if Flickroll is at 5.2) probably not the issue, but might be a question to ask Dynon. Did this cold DSAB failure happen with your system both at 5.1.1 and 5.2?
Really just grasping at straws here, just talking it through hoping to stumble onto something. Maybe this thread will give you a few more questions to ask Dynon as they test it.
I've got the airplane down for various maint items (playing with my wingtips and pulling the mag for 500 hr service) but I can power up the avionics when I get home Tuesday, and see if I get any warnings...the hangar has been C-C-C-Cold lately, so it'll be a good test...then the heat goes on! Will let ya know if I see any oddities!
Hoping you get some good news soon!
Cheers,
Bob