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Old 09-01-2015, 01:30 PM
Xpress.. is offline
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Hitec RCD CSR
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United States, CA, El Cajon
Joined Mar 2008
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Quote:
Originally Posted by robbinsp View Post
I have two 7950s that I have to run on a123 because they glitch on hv
What receiver are you using?

There is a known compatibility issue with Spektrum powersafe receivers, but only with the powersafe receivers, on HV (in which case, we have the fix).

The minimal load jitter on HV is a non issue.
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Old Yesterday, 12:48 AM
RcwBone is offline
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Xpress what would that fix be? Velcro or somthing electrical?
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Old Yesterday, 05:27 AM
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Happy contrails
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Near Louisville, KY
Joined Jan 2006
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Quote:
Originally Posted by ЯК Attack View Post
Where do you guys buy your MKS's?
Here are some recommendations from good sources:

http://extremeflightrc.com/MKS-Servos_c_509.html

http://www.3drchobbies.com/product-category/servos/mks/

I have been using JR NX6421's with good success, their double gear thickness is helping in the battle of gear wearing issue all servos are having. Now on something like this 88" Edge the 6421's are overkill you can get away with less torque, JR8911's are a good choice if you want an alternative.

Jeff
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Last edited by jwilliams; Yesterday at 05:39 AM.
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Old Yesterday, 08:39 AM
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Fly hard, land soft ;)
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Joined Aug 2011
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For the 88" Edge or any airplane this size, I would definitely recommend the HV777s. I ran them in my 91" Extra and didn't have any issues. The HBL380s would work too, but there is no need to have almost 600oz of torque in a 50cc airplane. The 777s are a perfect amount at about 520oz. This is the 91" Extra with 777s:


Extreme Flight 91" Extra 300 EXP at Joe Nall...
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Old Yesterday, 10:40 AM
Xpress.. is offline
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Hitec RCD CSR
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United States, CA, El Cajon
Joined Mar 2008
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Quote:
Originally Posted by RcwBone View Post
Xpress what would that fix be? Velcro or somthing electrical?
There's 2 different instances that we know about that people experience with certain 7XXX series servos:

1. Minimal Load Litter. 7XXX series are high resolution servos and as such, are prone to what is known as a "Minimal Load Jitter" which can be identified as the servos oscillating back and forth a minute amount at center. This is because the servos high resolution circuitry is trying to adjust for the slight position variances in the gear teeth. I've typically only seen it with servos that have hours on them and on bigger airplanes running longer 3D arms. As soon as you get airborne and airflow moves over the surface, the jittering stops and the servo is rock solid. One simple way to test for Minimal Load Jitter is to just push on the control surface slightly and see if the servo stops jittering. You can also fit a piece of the fuzzy loop side of velcro between the control surface and a fixed surface on the airplane (such as between the horizontal stab and the counter balance) to impart a load upon the surface which usually keeps the servo quiet.

2. Glitching. The same 7XXX series (mainly the 7940, 7945, and 7950) are prone to glitching, or random jumping (1" or more at unpredictable intervals) when used in conjunction with long servo leads that are of poor quality. Poor quality leads being low strand count and not featuring high quality gold connectors, typical HD extensions do feature high strand count wiring with gold connectors. I have seen instances where people switched from standard duty extensions to HD extensions and the glitching went away entirely.

The other glitching instances are when used with PowerSafe style receivers from Spektrum, even when using HD gold connector extensions, on High Voltage. There seems to be some sort of problem here when using long extensions but is easily remedied by using a Signal Booster. A Signal Booster ramps up the signal voltage coming from the receiver and sends it down to the servo so that it sees a very strong and clear signal. No known issues with other receivers on HV, just the Power Safe for whatever reason.
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