Brian and others.... this is NOT a suggested cause, just an anecdote of what went on in ~about~ 1966. We were building All Weather Landing Systems for a large airplane. We were having very weird failures during shake tests and burn-in, seldom consistent. Almost always, different symptoms. And when we troubleshot and repaired the units, it was not the same potted module that failed. There were as I remembered 6 different modules out of 150 on 9 different boards.
I started keeping the module we replaced and when I had time, I would stare at them and puzzle over them. The main thing these had in common was a tantalum capacitor. One of the junior, trainee techs, who went on to be a leader at John Fluke company, took a bunch of those bad modules apart. We could not test the parts at that time, but the capacitors in the modules that failed were all the same brand. One of 4 or 5 brands that were specified by the buyer of the AWLS. We could not "Change the specs and delete the brand" officially, but he went over to assembly and sort out this brand from the boxes and set them aside (several hundred). A few days later, the random failures stopped.
So, with permission of our bosses, we had boards assembled with un-potted modules built with capacitors from that manufacturer. These were then run through burn-in and shake, and before the environmental (heat and cold) part of the test got started, we had massive failure - the slug in those capacitors was coming loose and failing. The engineers "resigned" the module, giving it a new part number. and specifying a particular brand of capacitors to be used. --- Landings successful.
End of semi-off topic. All this to say -- think INSIDE the box. Do not get frustrated. Try to be VERY specific about what is done before,during and after the failure. I will start testing mine, and keep a log or diary of everything I do with the microHD until I figure a pattern. But right now, I do not have the time to do it right. ONE THING I will try, is putting a large filtering circuit on the power line coming in and also make the power in connector VERY solid and secure. It has appeared that my box and cable gets moved when checking to see if everything is going OK, and it seems the next timer disappears. (That being said, I still have only gotten 3 timed recordings since I got this unit - but no time to figure out why.) Again, my location, power, RF, heat / cold situation is UNIQUE. I am not blaming the box. It is nice to use at night when the sun goes down, and we can watch a few minute of TV with the inverter being on. (so far, TBN, Daystar, GOD-TV, and Sonlife are the first four in my Favs list, and all we take time to watch.) Both the TV and microHD are 12VDCV powered.
