Robbe FS 500 Servo problem
04-13-2003, 01:02 AM
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Robbe FS 500 Servo problem
When I was stationed in Germany I picked up a few Robbe FS 500 mini servos to use for throttle servos. As far as I know all Robbe servos are actually Futaba servos and Graupner servos are actually JR servos.
The thing is some servo models say Robbe/Futaba and others just say Robbe, so maybe these aren't Futabas at all.
On to the problem...
Last weekend I was flying Great Gonzo and the throttle servo died. I completed the first flight with no problems and shut off the engine using the throttle cut-off on the tx. The next flight the throttle servo just didn't work. That seemed really strange to me because it didn't fail in use. It was the next time I turned on the radio that it failed.
When I got the plane on the bench, the servo would work sometimes and then not work. Seems like a short or something. Other servos plugged into the same channel seemed to work fine, but I never checked with the engine running.
So I switched it with another servo of the same make. That one worked for a couple days. Today it just started doing its own thing. It would oscillate back and forth with no command from the tx - always with the engine running. All the other controls worked fine. It first started when the aircraft was flying and when I was checking it on the ground it did what I described. Additionally, I moved the throttle to full and it moved there but took a while and was oscillating the whole time. When I pulled the throttle back to idle it took about 5 seconds before it started to move.
I replaced the servo with a Graupner/JR C341.
If the Robbe servos are just crap that's fine. What I'm concerned about is that it may be the receiver or tx that's acting up. My other planes are working fine using the same tx.
The receiver is a Hitec 555 which has been flawless up to now and hopefully still is. The tx is a Futaba 8UHP heli. I'm really hoping it's just the servos are defective and I can toss them out.
Has anyone else used these servos and can you tell me anything about them? Also, any constructive/diagnostic feedback is welcome. If you need more information just ask. The battery is a 4.8 v 300 something mAh. These servos have never been hooked up to more than 4.8v.
Thanks
- Paul
The thing is some servo models say Robbe/Futaba and others just say Robbe, so maybe these aren't Futabas at all.
On to the problem...
Last weekend I was flying Great Gonzo and the throttle servo died. I completed the first flight with no problems and shut off the engine using the throttle cut-off on the tx. The next flight the throttle servo just didn't work. That seemed really strange to me because it didn't fail in use. It was the next time I turned on the radio that it failed.
When I got the plane on the bench, the servo would work sometimes and then not work. Seems like a short or something. Other servos plugged into the same channel seemed to work fine, but I never checked with the engine running.
So I switched it with another servo of the same make. That one worked for a couple days. Today it just started doing its own thing. It would oscillate back and forth with no command from the tx - always with the engine running. All the other controls worked fine. It first started when the aircraft was flying and when I was checking it on the ground it did what I described. Additionally, I moved the throttle to full and it moved there but took a while and was oscillating the whole time. When I pulled the throttle back to idle it took about 5 seconds before it started to move.
I replaced the servo with a Graupner/JR C341.
If the Robbe servos are just crap that's fine. What I'm concerned about is that it may be the receiver or tx that's acting up. My other planes are working fine using the same tx.
The receiver is a Hitec 555 which has been flawless up to now and hopefully still is. The tx is a Futaba 8UHP heli. I'm really hoping it's just the servos are defective and I can toss them out.
Has anyone else used these servos and can you tell me anything about them? Also, any constructive/diagnostic feedback is welcome. If you need more information just ask. The battery is a 4.8 v 300 something mAh. These servos have never been hooked up to more than 4.8v.
Thanks
- Paul
