My ARINC 429 module went off line again recently. I'd made a few changes but became suspicious that dirty power is the culprit. For some reason, I'd never put a filter cap on the alternator. Last night I pulled up one of my videos on my iPad and the alternator whine was very audible. On a few others, noise from the trim motors can be heard. It didn't seem to be very noticeable when I watch it on a desktop and think it's because I don't turn the volume up very much on my PC. Some of the videos are recorded with an audio cable connected to the copilot's receive audio and others are recorded using the GoPro's mic. Also, I'm not hearing alternator whine in my headsets.
The commercially available filter cap is 15 microfarads and connects directly to the B lead on the alternator. I pulled some caps out of a PC power supply that were 470 uF and will try one of those connected at the engine buss fuse panel (which is much closer to the avionics).
Update-flight and video seem to indicate the whine is reduced but pitch trim motor noise is still audible. The ARINC module stayed on line. CHT temps are
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