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Old Oct 25, 2010, 10:01 PM
Love my scale Whirlybirds
Keyrigger's Avatar
Mississauga, Ont., Can.
Joined Sep 2009
2,385 Posts
Question
Some bad luck with a GP 780

Has anyone heard of or experienced the following? A properly set up GP 780 and DS420 working fine then suddenly the servo fails (fortunately at a neutral position) and it does not move with any stick input. Since it could have been a bad servo, a HiTec HS-56MG was swapped out with the standard precautions of setting the gyro to analog before connecting the servo. After one half of a battery, the servo did the same thing only this time it was full right (or left as it doesn't matter that much) when it failed. The common denominator was the GP 780 and if this helps, it seemed to give me a bit of gain trouble just before the servo failed in both cases. Thanks.

Don
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Old Nov 22, 2010, 11:27 AM
Registered User
Berkeley, CA
Joined Oct 2004
1,895 Posts
Check the servo settings, make sure it is at 1520us pulse rate. If it is set to the 760us narrow pulse frame rate, it will burn out the non 760us servos. To set the gyro at 1520us permanently, you have to move the rudder stick to the right 3 times, check the manual for details.
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Old Nov 22, 2010, 05:53 PM
Love my scale Whirlybirds
Keyrigger's Avatar
Mississauga, Ont., Can.
Joined Sep 2009
2,385 Posts
Thanks. The gyro has been replaced by Align, through the LHS. There seems to be a lot of hoops to jump through before anything can be exchanged, I think, to make sure that the components came from their kits. The Hologram sticker is the serial number of the heli and that needs to be included for verification that the part is not a knock-off. Oh well, what ever.

Don
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Old Nov 22, 2010, 06:00 PM
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Irvine, CA, USA
Joined Oct 2000
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Not so much an issue with the knock off's, but gray market products that didn't go through the proper distribution channels.

Glad you got it replaced. This is an awesome gyro once properly setup. etarter is right, make sure it's set to the 1520us pulse rate. That is the #1 cause for servo failures.
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Old Nov 22, 2010, 11:50 PM
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zen@lanset.com's Avatar
Berkeley, California
Joined Jan 2007
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I'm glad I didn't try to use my 780 without knowing about setting the pulse width.
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Old Nov 23, 2010, 07:41 PM
Love my scale Whirlybirds
Keyrigger's Avatar
Mississauga, Ont., Can.
Joined Sep 2009
2,385 Posts
I usually don't miss something as important as the setting for the pulse width (I have set up a few of these and also have a Quark with similar setup options) and thanks for bringing it up as a possibility for the reason it failed. It is great that guys can point out something that can be very easily overlooked and can bring things to a very expensive halt. In this case, the gyro was setup and working correctly for the better part of four weeks (not too many flights but enough to show that it was working great) so why it failed will be something that Align will eventually figure out.

I just bought a second 250 SE and the GP780 gyro on it is working just fine. The only difference in the setup of this and the heli that the failed one was on was the endpoints. So far, as long as it is acclimatized to the area it is flying in, my 250 holds very, very nicely. It does take at least 10 minutes to warm up or cool down so that it gives stable inputs to the tail servo. It is a very easy to setup gyro, in fact, I find it easier than an Eflite G110, lol. Take care and thanks for the input.

Don
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