tripower222

My Feedback: (5)

Recently I have had 2 servo failures same plane same servo position left flap channel 7. These are the only servo failures I have ever experienced the fact that it was the same servo position and channel bothers me. The failure seems to be electronic, just no movement but will bump when pluged in, will not hold position, and can be moved by hand as if they where not pluged in when powered. Dissasembly shows no discrepencies. The first servo had 2 hours (on this plane) befor failure the second had maybe 45 minutes. Both servos where S148's, receiver R617FS, radio 7C 2.4, battery nimh 6.0v. The servos where older but I dont remember how old, 1 was unknown the other was 12+ years old. I guess I am looking for some reassurance the problem is just old servos and nothing more. I was also wondering if maybe the older S148's don't like 6v rx batteries.

tcrowson

Do the servos work after removing from the aircraft? If they do then check the wiring to the servo. You might also check for binding in the flap or linkage.

Tas

tripower222

My Feedback: (5)

Ok Bax, now I am really thinking the receiver is killing the servos. I replaced the second bad servo with a S3004 everything worked fine I took it to the field turned the model on and the new servo was dead. The servo is sharing channel 7 with the battery useing a Y harness. I removed the Y harness and hooked an ohm meter to the terminals in every possible combination playing/wiggling in each configuration there are no shorts in the harness. I can think of nothing else that could be killing the servos other than the receiver. all servos that have died have the same symptoms.

tripower222

My Feedback: (5)

Bax, I think I figured it out tell me what you think it may also be worth a note in the manual. Attached are pics of the charge switch on the plane I do not know what brand it is, I purchased the plane used. The orange (signal wire) believe it or not does not disconnect through the switch. I use a Hobbico Accu Cycle Elite charger with a Futaba charge connector it can and I have plugged it in backwards, the charger tells me open circuit then I switch it. With the #7 servo sharing the y harness with the battery the orange wire is getting a high charge voltage for a few seconds before it says open circuit. I think this has to be the problem, Would a little over 7 volts on the signal side of the servo lead kill it? if so thats the problem. I guess I will just cut the orange wire on the charge switch.

Bax

My Feedback: (11)

The on/off switch will not cause the problem with your flap channel. If you plug the battery lead into any servo output on the receiver, it will deliver power as normal. If you plug it in backwards, nothing will work, but nothing will be damaged.

If you have a location where a servo continually becomes damaged, we'd look for some difficulty outside of the servo. Likely, you're getting flutter or the control surface is putting some kind of abnormal strain upon the servo. Perhaps the linkage is binding. The receiver may be having a difficulty putting out a good signal on that channel. If you have more than one servo plugged into the same channel, then it's possible that they are sinking too much current through the signal lead. That would degrade the control signal to the point that the servo won't have good position information. One servo may be affected more than the other. If the affected servo has no problems when plugged into a different channel or when operating alone, then there's your problem. However, your difficulty would not be through the switch harness.