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5975 going full throw

Old 07-18-2005, 09:51 AM
  #1  
ccw
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Default 5975 going full throw

Hi guys,

I bought some 5975 karbonites and finally got to use them on my Freya heli.

The 5975 driving my throttle went crazy and decided to go full throw to WOT (and beyond) on me after the 2nd flight. I have ruled out interference/failsafe, wrong settings, etc. It all points to the servo. ATV/AFR is no where near 140%. I couldn't even hit hold and autorotate.

The servo also caused one hotstart - idle up was not engaged, throttle set to low, servo direction is correct. Battery voltage is above 4.8V (4 cells, GP3300s) as indicated by the 502 Gyro amplifier display.

The sticker says Rev 1.03 and the servo comes in the plastic box, so I assume that this is a later production servo and had 'programming issues' sorted out.

I am hesitant to use my other NIB 5975s now. Please advice. What could have caused this and what I should do with my servos.

I had previous incidents with the 5125, but damage was minimal as it was used for airbrakes on a glider.

I have a bunch of Hitec servos and really hope that Hitec will stand behind their product. This incident cost me a clutch and messed up my runninig-in of a brand new YS91St engine. I am not seeking damges but do need a solution and peace of mind.


Thanks.
Old 07-19-2005, 11:41 AM
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tohm
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Default RE: 5975 going full throw

Without looking at the servo, there is no way to tell what went wrong. I suggest you send the defective servo to a Hitec service center in your country to have it looked at. If you need to locate one, there is a list on our website under support.
Old 07-19-2005, 05:34 PM
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mglavin
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Default RE: 5975 going full throw

What are the OEM servo recommendations for the Freya helicopter? The 5975HB with Karbonite may not be the best gear-train material for this application.

The revision v1.03 digitals have no issue with MAX ATV settings. It sounds like you have a Futaba 9Z based on the AFR/ATV comment. Did you setup the MAX servo travel with ATV and then forget this setting and use AFR to adjust or fine tune the needed control input on all the channels? ATV should never be adjusted after the initial setup, use AFR ONLY...

It's possible the gear train has been damaged; it’s easy to inspect and verify this yourself.

You’re using a 4.8V, 3300mAh battery? New battery, NiMH’s have you cycled and load tested the battery? The Hitec digitals can reboot and rotate to extreme travel if the voltage drops below their minimum requirement. Do you have an ESV to load test the battery with a 1.5A load?


Old 07-20-2005, 01:07 AM
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ccw
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Default RE: 5975 going full throw

Hi Michael,

Thanks for your response.

I assumed that the geartrain would be sufficient given the amount of torque the servo is spec at. Besides, I think the geartrain issue has been touched on earlier - that this same set of gears is also used on the newer/current servos (I can't remember which, off hand). I don't fly 3D and have not even begun to stress the heli - only smooth, medium power circuits to run-in the engine.

I actually went with karbonite becuase I was concerned about the wear and tear of metal gears on a heli. Was that a bad move?

Besides, in this case it was used for the throttle - very little loading. I've checked the gears, no problems at all. In fact, I tried to duplicate the full throw behaviour on the ground with the programmer and Rx and can't.

Yes, you are correct, I am using a 9Z. Both ATVs and AFRs are set to less than 100%. In tis case, AFR was not used on the throttle.

I know that it went full throw because it had enough torque (and I'm sure the vibrations helped out) to unscrew my throttle arm twice. It also shows that my end points are far from 140%.

The battery is newly assembled and cycled. it was even formatted by a Orbit Microlader and cycled a few times before use. I have an online voltage display on the 502 gyro amplifier and it never dropped below 4.8V with all servos moving and attached to the linkages. Besides, I also have other Hitec digitals (5975s on cyclic and 6965 on collective) onboard that didn't exhibit this behaviour.

Also, I had one hot start, ie: went to WOT. I always check the voltage before flight and none of the servos are moving during startup (except maybe the tail rotor). So that should also rule out the battery.

So, I think at this point we can safely rule out geartrain and voltage. I also make it a point to reset all Hitec digital servos with the programmer before using them.

I have two more 5975s (which seem fine for now) on this heli and a few more NIB and would like some peace of mind.

Hope you or anyone else at Hitec can help out.

Thanks!
Old 07-20-2005, 06:59 PM
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mglavin
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Default RE: 5975 going full throw

The Karonite gear-train is capable of withstanding the servos rated output in ideal circumstances. However the Karbonites do not seem to absorb shock loads as well as anticipated. The Karbonite gear-trains are tight out the gate and wears better than anything else on the market to the best of my knowledge. The Karbonites are not replacements for metal-gear applications…

For throttle applications the Karbonite is well applied IMO.

You noted that AFR was not used to set throttle servo travel arc. It should have been. AFR is used across all channels to adjust the required end-points for all applications, conditions and such. ATV is used initially to setup the radio/servo travel arc maximum allowable throws. With this in mind its desirable to use as much travel volume as possible to realize maximum system resolution. *****g out ATV to 130% is desirable providing binding does not occur, in the case of binding changing the servo arm length allows for MAX travel volume or ATV. Increased travel of the servo arm realizes more precise movement of the mechanical setup and control interaction. Limiting the servos travel arc with ATV, minimizes the control signal pulse steps and this effects resolution, more is better. The Hitec programmables can work around this shortcoming with programming the end-points, the servo will subsequently recognize MAX control input no matter how small the offset from center or neutral maybe, nothing else in this market can offer this very desirable feature.

Do you have a Governor in series with the throttle servo?

If you realized WOT and nothing else was moving, you may have a defective servo or something is possibly interacting electrically. Things like poor-dirty-loose electrical connections have been known to cause this kind of problem.

What do you specifically mean unscrewed the throttle arm twice, the throttle linkage screw backed out? Did you use a thread locker like Loctite? How does this factor into realizing full throw and less than 140% ATV percentages? Minimal torque (almost none) should not be required to push the carb throttle body back and fourth.

Are you load testing the battery with a 1.5 Amp load and noting the voltage at this time? Static voltage readings mean little, the value under load provides a bigger picture. The gyros voltage display information is useful but not gospel.

The battery is comprised of 3300mAh Nickel Metal cells? You load tested and or cycled at what discharge current to what termination voltage. That’s a lot of battery for a flight pack. NiMh cells have to come to life, repetitive cycles form the battery. Two cycles is inadequate IMO, I would go for at least four. BUT if your able to prove the battery with a discharge load of at least 1.5A sustained for sixty seconds it should be good to go.
Old 07-23-2005, 09:34 AM
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ccw
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Default RE: 5975 going full throw

I use AFR almost everywhere else, except throttle because that's where my throttle curve comes in and I have the habit of setting the highs and lows on those curves, so, nah - no fashioned curves, no governor.

I'm pretty sure the battery is more than enough for this application. These are the GP3300s, identical cells and battery construction (end to end, no solder tabs) to what I use in my 120A F5J planes. So, 1.5A is definitely not an issue here. Wires are heavy guage as well.

All servos, connectors are brand new and clean - and No, I don't even use a switch.

Besides, as mentioned before, if it's the battery, why didn't the rest of the Hitec digitals reset?

I'm pretty sure it's the servo, and I will send this particular one back to Hitec, but I really need to know if this is a 'problem' servo in terms of software or otherwise. I have a few more NIB ones and also another set installed on my Nova.

So, can someone tell me if the 5975Hb is an ok servo, that what I experienced is an isolated incident, or is this a 'known' problem? I'm not making waves, just need the peace of mind. A PM is fine. I don't like rebuilding helis!

Thanks..
Old 07-23-2005, 10:46 AM
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mglavin
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Default RE: 5975 going full throw

AFR works contiguous with your throttle curve and does not limit same. The reason AFR is used across the board is to allow mixes, offsets, curves, conditions and the like to share end-point values defined in ATV thus not allowing an offset or movement outside the original predetermined value of ATV or end-points. It's plausible for the throttle servo to travel beyond your defined parameters otherwise, unbeknownst to you. EXPO is a feature within AFR is user assingable and does not have to be activated and should not in your case for throttle.

May I suggest using the "SYS" menu and the "SRV" button and bring up the servo test function. This allows you to see the servo functions graphically. While in this mode move all the sticks individually, throw the condition switches and the rate switches and note if the throttle position changes. I found a problem with a modeler’s set-up like this. He some how activated a mix that was on all the time, when more than 50% throttle and rudder deflection were used the throttle came back to fast idle. It was the strangest thing as we could not see it on the ground; we'd check everything and all appeared to work fine.

Certainly it's possible your servo is defective I apologize if I was leading you down another path, however in most cases of traveling to end-point the problems are not the servo in of itself.
Old 07-27-2005, 10:15 AM
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ccw
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Default RE: 5975 going full throw

Hi Michael,

I checked through everything and all is fine, no problem with extreme throws at all. No strange mixes. Even my cyclic to throttle mix or rudder to throttle mix is <10% at this point. Besides, the servo went to full throw w/o any additional inputs (no switches, only gentle smooth inputs from the sticks).

I certainly appreciate any inputs, but I think the only conclusion in this case is a defective servo.

The question is: shall I return all my NIb 5975s along with this defective servo to Hitec for a comeplete run through or reprogramming of a newer ver software- will it make any difference? Will Hitec entertain my request for the NIB servos?

Is ver 1.03 safe from the re-programming issues? Does re-programminig happen under any other conditions?

Thanks.
Old 07-27-2005, 10:47 AM
  #9  
mglavin
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Default RE: 5975 going full throw

There is NO reason to update v1.03 servos...

Hitec USA is not authorized, nor obligated to service and or warranty any items used and or purchased outside North and South America. Contact your local dealer or distributor.

The 5975's were superseded by the "6900" series Karbonites and are no longer available. There is little to no difference between these old and the new..

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