R790 vibration problem?
10-06-2006, 10:28 PM
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R790 vibration problem?
Hi Danny:
Have a new R790 PCM on 6 volts and 6 Hitec servos. Was getting a gas plane (w/ ignition) ready for the first flight today and noticed that the servos were showing uncommanded movements. If I gave it full aileron and then released (or neutralized) the stick, the ailerons would not return to neutral for a few seconds and jumped around a bit in the process. Very erratic (uncommanded) movements at times (not all the time though) on different channels (in this case aileron and throttle). These problems were noticable with 15 seconds of putting in the commands (didn't have to wait long to see the problem). NOTE: all of this happened with the engine running and there was clear vibration in the fuselage. While I was setting the airplane up (engine NOT running) over the past week, I didn't detect any anomalies with the receiver (first time it has been used). I am running two other R790's in other glow engine airframes with no problems.
To me, it looks like there is a vibration related issue with the receiver OR an issue on gas airplanes with ignitions. Could you let me know your thoughts on this.
Teryn
Have a new R790 PCM on 6 volts and 6 Hitec servos. Was getting a gas plane (w/ ignition) ready for the first flight today and noticed that the servos were showing uncommanded movements. If I gave it full aileron and then released (or neutralized) the stick, the ailerons would not return to neutral for a few seconds and jumped around a bit in the process. Very erratic (uncommanded) movements at times (not all the time though) on different channels (in this case aileron and throttle). These problems were noticable with 15 seconds of putting in the commands (didn't have to wait long to see the problem). NOTE: all of this happened with the engine running and there was clear vibration in the fuselage. While I was setting the airplane up (engine NOT running) over the past week, I didn't detect any anomalies with the receiver (first time it has been used). I am running two other R790's in other glow engine airframes with no problems.
To me, it looks like there is a vibration related issue with the receiver OR an issue on gas airplanes with ignitions. Could you let me know your thoughts on this.
Teryn
10-06-2006, 11:29 PM
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RE: R790 vibration problem?
Hi Danny, I also had a similar problem with my R790 Rx.
It was installed in a Double Vision biplane with a DA-50 engine. This is a new plane and new radio installation. Hitec 5945 x 4 for ailerons and 8611A for elevs and 8611 for rudder. Fromeco Li-Ion & regs for Rx and Ign. 9303 Tx with syn module.
Range tested fine with engine off and at high idle. (more than 50 paces with Tx antenna collapsed).
Second flight seemed as if I barely had control (ie: no solid feeling, seemed to wander a bit) so I landed immediately. I taxied back and stradled the plane to check the controls. Thats when the Rx went in and out of failsafe. I was checking the controls at partial power and then the engine went to low idle (failsafe position), then back to partial power, then idle, etc... This went on for about 10 seconds and I shut everything down. This was happening with the Tx antenna fully extended and only 2 feet away above the fuse.
I took out the R790 Rx and installed a R649 Rx instead and have flown the plane at least a dozen times without any issues.
I planned to put the R790 into a foamy or something to test it further but just have not gotten around to it.
Are there any issues with the R790 Rx that we should be aware of? Of course, some other flyer said just change the channel and try again...Yeah, Right! only if he volunteered his plane!!
This synthetic setup is ideal for fly-ins but not if I can't get a solid link!
Dan
It was installed in a Double Vision biplane with a DA-50 engine. This is a new plane and new radio installation. Hitec 5945 x 4 for ailerons and 8611A for elevs and 8611 for rudder. Fromeco Li-Ion & regs for Rx and Ign. 9303 Tx with syn module.
Range tested fine with engine off and at high idle. (more than 50 paces with Tx antenna collapsed).
Second flight seemed as if I barely had control (ie: no solid feeling, seemed to wander a bit) so I landed immediately. I taxied back and stradled the plane to check the controls. Thats when the Rx went in and out of failsafe. I was checking the controls at partial power and then the engine went to low idle (failsafe position), then back to partial power, then idle, etc... This went on for about 10 seconds and I shut everything down. This was happening with the Tx antenna fully extended and only 2 feet away above the fuse.
I took out the R790 Rx and installed a R649 Rx instead and have flown the plane at least a dozen times without any issues.
I planned to put the R790 into a foamy or something to test it further but just have not gotten around to it.
Are there any issues with the R790 Rx that we should be aware of? Of course, some other flyer said just change the channel and try again...Yeah, Right! only if he volunteered his plane!!
This synthetic setup is ideal for fly-ins but not if I can't get a solid link!
Dan
10-07-2006, 03:22 PM
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RE: R790 vibration problem?
UPDATE to my problem above: we replaced the R790 PCM receiver with an crystaled R770 PCM and saw less of a problem on the ground. However, in the air the receiver started locking out just like the R790. I was able to get it on the ground with no problem. We inspected the engine area and noticed that ignition module was in contact with an engine mount bolt protruding through the back of the firewall AND the spark lead was touching one of the mufflers. After fixing these, the problem went away. I just have to put the R790 back in and try it with that but I don't expect any problems.
10-09-2006, 08:30 AM
#4
RE: R790 vibration problem?
Good to hear that the problems are getting worked out. To answer the other question, we haven't seen any trends of any problems with the 790 receiver, they have been working very well.
