HS-605 Oscillates
 

I have 2 new 605's mounted as standard twin aileron servos. I have a problem with only one of them. They have 5 flights on them.

Present setup:

Futaba 9C radio
Futaba 149DP PCM receiver
Oddino Perfect Switch w/5.7 Volt regulator.

Problem - During pre-flight check, I noticed that if I quickly "slap" the aileron stick to one side or the other, the left servo will bounce, or oscillate, at the desired end point, until it calms down after several seconds. The surface bounces back and forth while it oscillates, ranging from about 25% to 50% of the total throw, so in flight this would not be fun, especially with flaps. Right servo and other servos on the plane are fine.

- This occurs about 1 out of 4 times I hit the stick quickly. It happens nearly every time when flip the flaperon switch. I'm guessing that the instantaneous change in signal makes that one servo bounce. I swapped left and right aileron servo connectors, and the problem stays with that one "problem" servo. I checked it on low rates as well, and was surprised it does it on low rates also. The servo is not being driven too far. Normal operation is smooth when I move the stick normally (slowly). The right servo is totally fine.

I could not reproduce this problem using my ACE servo cycler (varying the input voltage from 4.8-6.5 volts) or with my HFP-10 Hitec tester/programmer, either, no matter how fast I tried to change the servo position. I guess they do not change the signal as fast as my flap switch! Note, the HFP-10 shows the receiver voltage to be running approx 5.35-5.60 volts while the servo is connected.

Should I just mail this servo in for repair? I can pick up another at Venture Hobbies (my LHS) in the meanwhile. I don't mind having a spare on hand.

Thanks

RE: HS-605 Oscillates
 

I think this is one of the reasons Hitec discontinued the 605. I have one that does the same thing.

RE: HS-605 Oscillates
 

I would ship the servo to Hitec for evaluation and or a possible free replacement.

The problem maybe exasperated by speed and the load in motion your exposing the servo too. Possibly surface load momentum is causing the servo to overshoot its commanded position. Remember this is simply an inexpensive standard 3 pole motored servo, an early version to boot.

RE: HS-605 Oscillates
 

Thanks, Mike. I just got back from the post office, having mailed it to Hitec.

Actually, this HS-605 was purchased in September of 2003, and is should have been one of the last ones made before they obsoleted it. The last 605's supoosedly had improved electronics to improve centering. Perhaps this particular one was older and didn't have the good stuff! I was told at RCHTA that those fixes have been incorporated into the new 635HB, which also has Karbonite gears.