RE: DX8 telemetry RPM pickup for Gas engines - SOLVED!!
Last month, I had a twitching rudder on my 1/4 scale EAA Biplane(ThunderTiger 1.20 2 stroke engine). Everyone at the field swore that it was RFI, some donated those ferrite donuts but the twitching continued.
On returning home, I did a "wire shake" test and sure enough the rudder twitched. Thinking there was a bad solder joint, I changed the connectors from a point that was right inside the case. Hooked everything up and Lo and behold, the rudder still twitched when the wire was jostled. I took the servo back out, and this time hooked it to a test receiver. What I eventually found was the the bad solder joint was on one of the spider legs of the micro-chip. pushing down on the chip I had solid performance. Now this was not a high priced Futaba servo, more like a mid range knock off of a HiTec standard servo, but it sure served as an eye opener.
KKKKFL