Neal@F14
Well Known Member
The RV-6 I recently bought is built with the EXP Bus II system (which I'm really not too thrilled with), and after installing my Garmin 196 GPS into the panel with a new Airgizmos dock to replace an old Bendix monochrome SkyForce unit, I noticed that the avionics bus connection I used to power the GPS with, seems to be showing almost 1 full volt of drop between the battery and the "AB2" terminal on the EXP Bus board that I am using to power the GPS. The built-in voltage measurement you can put on the screen of the Garmin 196 has generally been dead-nuts accurate, I've checked what it displays against my Fluke DMM in the past and they both matched to the tenth of a volt.
Has anybody else out there who runs the EXP Bus also noticed a significant voltage drop across the polyfuses? I haven't yet tried measuring across all the polyfuses on the EXP Bus circuit board, since I just noticed the low voltage on the GPS display first, and I had already reassembled the EXP Bus into the panel. I'll do more testing this weekend, but it sure seems to me that a 0.8-1.0 volt drop in normal operation for a GPS that draws less than 1 amp, and is connected to a supposedly 3 amp polyfuse is too excessive to be good.
Has anybody else out there who runs the EXP Bus also noticed a significant voltage drop across the polyfuses? I haven't yet tried measuring across all the polyfuses on the EXP Bus circuit board, since I just noticed the low voltage on the GPS display first, and I had already reassembled the EXP Bus into the panel. I'll do more testing this weekend, but it sure seems to me that a 0.8-1.0 volt drop in normal operation for a GPS that draws less than 1 amp, and is connected to a supposedly 3 amp polyfuse is too excessive to be good.