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Spectrum servos on 72 Mhz?

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Spectrum servos on 72 Mhz?

Old 05-28-2008, 03:47 PM
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djr1007
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Default Spectrum servos on 72 Mhz?

I bought several of the ds821 Spectrum servos off the bay (selling in lots of 4, good price). Anyway I put 4 in a new ARF using my standard 9303 and Hitec reciever. On the bench there was no problem, outside no problem, started the engine (YS45 on a pipe) and I got a little flutter. I went to full throttle and all servos went totally nuts!. I began the tedious job of trying 3 different switches, 3 different recievers, plugging/unplugging each servo indiviually, nothing made any difference.
I took the plane to the field and a friend who has a 9303 converted to 2.4 gave me a reciever, we bound it to his transmitter, and no problem at all, no flutter.
Could these servos be boarder line sensitive? works fine on the bench, goes wild with full throttle.
BTW, no metal to metal, not even the header to pipe, and the attena runs immediately out the fuse and off to the stab. Range check yeilds same results, ok with the engine off, servos gone wild with the engine running.
What do you think? anyone else seen this.
Thanks.
Old 05-28-2008, 05:48 PM
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allans
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Default RE: Spectrum servos on 72 Mhz?

Did you use a freshly charged battrey in your plane ? And what level was the battery in your 2.4 gig plane?
This is a common occurrence with new or overly cherged batteries . I see this all the time with spectrum servos and jr radios.
Move sticks 100 times to lower the level in the plane battery and try again.
Old 05-28-2008, 06:11 PM
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djr1007
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Default RE: Spectrum servos on 72 Mhz?

Thanks for your input. I used two different NiMH 6V packs, freshly charged and load checked. It was one of these packs used for the 2.4G test.
Old 05-29-2008, 05:55 AM
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bps
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Default RE: Spectrum servos on 72 Mhz?

Check your crystal in the Hitec receiver. Sounds like an electrical connection to me.
Old 05-29-2008, 09:00 AM
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Flying freak
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Default RE: Spectrum servos on 72 Mhz?

I can tell you for a fact that the spectrum 821's WILL work with a jr 9303 but i have no experience using it with a hitec rx...

Steven
Old 05-29-2008, 04:08 PM
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djr1007
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Default RE: Spectrum servos on 72 Mhz?

The three recievers I tried were 2 hitec and 1 JR, each with their own crystal. This has really got me bum fusseled!...I've just got to be missing something stupid.
Old 05-29-2008, 05:21 PM
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Lomcevak Duck
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Default RE: Spectrum servos on 72 Mhz?

I use the spektrum ds821 servos on 72 MHz without problem. I'm using Futaba TX and RX.

It seems to me the common denominator is your 72 MHz gear. And since others have used these servos with 72MHz, it makes me wonder if you've got an RF noise problem wreaking havoc on your 72MHz gear and the servos are not part of the problem, just showing a symptom. Try hooking up different servos and repeating the test to see if they go nuts. That would be proof that you have a general problem with RF noise when the engine is running.
Old 06-01-2008, 08:04 PM
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djr1007
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Default RE: Spectrum servos on 72 Mhz?

Duck
I'll try it, nothing to loose.
This 9303 works fine with all other receivers and planes I have. I don't want to think it, but I wonder about that YS45 on the pipe. I'm just going to swap in all new gear like you suggested Duck (not just the servos) and see what happens. last step will be to swap that YS out with a OS.
Thanks everyone.
Old 06-01-2008, 10:30 PM
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polkfam
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Default RE: Spectrum servos on 72 Mhz?

looks to me like a vibration problem. balance the prop, full throttle wjth unbalanced prop will cause many problems. insalate the reciever.
Old 06-02-2008, 08:10 AM
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BarracudaHockey
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Default RE: Spectrum servos on 72 Mhz?

All servos work pretty much the same way. Once the signal is decoded its all the same. Its sent to the servos as a pulse, the width of which determines the servo position for that cycle. In short, the servos are blissfully unaware whether that position information was encoded and decoded using ppm, pcm, or a 2.4 protocol.

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