RE: Edge 540 2nd flight almost last
Silversurfer,
Beginning to think you are right, except that I have now tried a different brand receiver and still have glitches caused by the JR8611. I did some oscilloscope measurements over the weekend. Not sure what they mean, but maybe someone will recognize something that I am missing.
Voltage measured between ground and signal wires with servo plugged into one side of a "Y" and oscilloscope connected to the other, plugged into channel 4.
Receiver = Futaba R127DF
No Load Signal 6.72 V Ground 0.0 V
HiTec 5645 Signal 6.0 V Ground 80 mV
JR8611a Signal 6.48 V Ground 0.0 V
The HiTec caused no observable gliches. The JR caused sporadic, violent glitches. There was a fairly constant noise ripple running through the pulse at about 5.68 V, with the JR.
Receiver = Futaba R138DP
No Load Signal 3.04 V Ground 0.0 V
HiTec 5645 Signal 3.00 V Ground 480 mV
JR8611a Signal 2.70 V Ground 0.0 V
No glitches were observed with either servo despite the elevated ground voltage with the HiTec and the lowered signal voltage with the JR. This would seem to be the result of the PCM receivers ability to ignore bad data. However, the original, in-flight problem occurred with this receiver.
Receiver = FMA Fortress 2000
No Load Signal 3.12 V Ground 0.0 V
HiTec 5645 Signal 3.12 V Ground 80 mV
JR8611a Signal 3.00 V Ground 0.0 V
No glitches were observed with the HiTec servo connected. Regular, minor glitching occurred when the JR8611a was connected (movement of the rudder back and forth about 1/4 inch).
Although the FMA receiver did not exhibit the violent glitching that was observed with the JR8611a, it still glitched regularly in a minor way. My conclusion at this point is that the 8611a has got to go. A different brand, non PCM receiver did not eliminate the problem. My flying buddy has seen the same type minor glitches with his WH Extra and the JR8611. I think he is using a HiTec receiver, but I'll have to check and make sure. He has not been willing to fly the plane until the problem is resolved. Given that we are both seeing the problem, it does not seem likely that I have a "bad" servo, but the only thing left to do is send it back to JR for them to test. It is useless to me at this point. I hope all this has been useful. I am going to go with the FMA receiver and replace the 8611, probably with a HiTec servo.
Note: Glitches occurred with no transmitter control stick movements. Glitches were observable as physical rudder movement and as changes in the pulse width on the oscilloscope. Normal pulse width (stick centered) was 1.5 ms at a frequency of every 20 ms for all receivers. Engine was not running.
Bill Gavin