may be a defective potentiator

[kaos]

I was playing with one of my TX with stock board. I found out the THR stick potentiator may have a problem that I never noticed before.
after I recalibrated a few times it shows the same thing. when I push the THR stick up there is a 'dead space' area at the bottom stick. the number won't change from -100 until almost reaching the 1st scale mark before the output start to increase from -100 and up. but center stick is still 0 and top sick is still +100. which means this will increase the response quite a bit when flying, only 2/3 of the stick movement from center to bottom is controlling the 100 scale range.
Is there any way to correct this? easy way.

[MikeB]

What are the numbers on the ANA screen corresponding to the throttle stick?
Maybe the throttle pot body has rotated, these numbers may helpp decide if that might have happened.

Mike.

[kaos]

The A2 shows -100 to 100 correctly. only the -100 does not change until the THR stick is moved close to the 1st scale mark which is about 1/3 of the total travel. But once it starts to increase from -100 then it is normal. mid stick is 0. from mid stick to top is 0-100.

The A2 shows 0000 until close to 1st scale mark then start to change to 0001-0010.... which corresponds to the number -100 to 0 change.
when output is 0(mid stick) A2 is 031E, 0718 (fulctuate a little from 0716-0718) at +100.

[ShowMaster]

I missed if this is a 9x or 9xr but try this.
Gently push on the pot or pot connections and see if the values change or become normal. Pot element connections are common on the 9X and the ones I've repaired we're throttle? I'm not sure why it's been throttle.
So far the 9xr has had pot body rotation but not open pot issues that I know of.
Mikes like my advice hopefully will help you track down what's going on.
SM


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[kaos]

I have not opened up the Tx, but the values are normal, only the bottom 1/3 or so (2/3 of the 1st scale mark) of the stick movement it is always -100. once the stick is raised beyond the 2/3 of the 1st scale mark, then the value changes correctly from -100 to 0(mid stick) then to +100 (top stick). this effectively makes the stick movement more sensitive (less total stick movement for -100 to 0.

when you say push on the pot, you are saying push/rotate the pot so it turns one way or the other along the axis?

[MikeB]

Your numbers are consistent with the pot body having moved (rotated), the 718 is low.

Mike.

[kaos]

Hmm, is there a pic some where showing how to turn the pot?

[Flaps 30]

Below is the picture of the throttle poteniometer. LH stick assembly.

Index tab shown at the top of the pot

The tab fits into the hole at the top of the plastic main gimbal assembly.

So unless the tab has broken off then it is highly unlikely that the pot will turn.

[kaos]

thx Flaps30 (and everyone responded here), so from what I can tell, there is no way to turn the potentiator without tear the whole whole thing apart?
or may be some how the metal axis of the potentiator can be turned inside the stick? may be it is the metal axis is off when placed in the the stick assembly. Is it easy to remove the metal axis from the stick and put it back to the stick after turned a little (in my case the stick will be turned a little toward the top end (when rotating) in relation to the current angle to the metal axis.? if there is some room for the potentiator at the top end.

PS:
Mike: what is the normal range of the ANA for all 4 sticks potentiator? It may be helpful for future reference in my notes.

[Flaps 30]

You cannot get the shaft wrong as it isn't round it is 'D' shaped and it fits into a 'D' shaped hole on the gimbal. It is idiot proof.

The way that the wiper is attached onto the shaft is also done in a way that it makes it hard to get it wrong during manufacture with regards to mechanical positioning.

[kaos]

great info (i have not tear apart a gimble so far ). in theory, if the potentiator has some head room at top end (in my case), I can modify the 'D' a little to turn the metal axis a little in the stick and change it? seems to me the stick is limited by the surounding wall of the gimble , if those walls are not there you can move the stick beyond the current limit?

[Flaps 30]

Quick answer to all of that is no..

IMO It's time to track down the problem, rather than try to physically alter what is there.

[kaos]

well, basically I just loose some 'effective' movement. Probably won't affect too much beside if I use this Tx to fly heli inverted will make the throttle/pitch control a little sensitive.
as for track down the problem. How do you propose to do that? As long as I won't destroy the potentiator or make it worse, I am open to ideas. Won't hurt to learn new things.

[wrenow]

Check out what the pot is doing with a voltmeter or ohmmeter, then you can isolate whether the pot is the issue. If the pot is doing what it is supposed to and not defective, and all connections seem OK on testing, then look into the programming (the servo limits set, mixes, curves, etc.) - lots of places to "oops" there, though it is pretty straightforward. I remember the guy in our club with a new TX that was getting all kinds of wrong, weird responses on most of his servos until we noticed he had it set to "Heli" mode. Oops. Lots of strange mixes for his simple boat, I can tell you. :O

Cheers,

Wreno

[ShowMaster]

If the pot element stiff wires or the PC board they're soldered to is stressed to much it can create a connection failure where the wire and pot element crimp connection is. His can happen when doing the 9x mods and the pot PC boards get moved around.
The ones I've repaired like new required the pot element to be removed from the metal pot body and the connection eyelet to be re crimped with a needle nose pliers, very very carefully to avoid breaking the element. In the past silver conductive paint was used to insure a good connection but not in the last year or more.
It's worked for me every time and I posts this fx some time ago.

Last resort fix ......
I first determined it had this condition by measuring the pots resistance while carefully pushing on the pots PC board or still leads. The pot would read normally with this side pressure and be bad when not.
It was an instant fix that's still working in these TXs a year later.
Not for the weak or timid but I had nothing to lose and it worked.




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[kaos]

the model setup is a blank one cause I reflashed the Tx and not touching any setting yet (and I just reflashed it once again to be sure).
so how do you use voltmeter to check the pot? what reading I should expect?
I would imagine if the wire is pinched or pc board is moved, it will give really weird output. but this only happens at the bottom stick area, the rest of the stick movement is perfectly OK.

[ShowMaster]

The pots are all 5k but in parallel. Using your meter on ohms take a reading from the center wiper to each side of the rudder pot at center. That reading should match pretty close to your throttle pot at center. Then move the sticks off center towards each end and see the resistance change. Do this with both pots to get a comparison reading. The throttle pot should be way different when moved towards the bad side.

The outside pot connections all connect to the+ 5v lead and -(ground) on the other lead. The center wipers all go to a CPU pin.
You can also measure the voltage swing with power on but risk a short circuit condition, very bad.
I'm not sure how to explain it simpler if this is new to you.
Putting pressure on the pot leads while having the throttle stick at the end having trouble for me, made the pot heal enough to see the servo travel the missing throw. This told me it was a pot element connection issue.
Try this first and report back what happens. If it goes "fix" the throw issue then the next step is difficult but works for me.
Looking at this pot you can see the end element connections. This is an older pot picture with the silver conductive paint but a damaged resistive element I copied, not my pot.
My fix has been to strip the pot down to this element and recrimp the end eyelets.

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[kaos]

Interesting, I had a chance to open up the Tx. I found there is a little 'slop' where the THR pot is mounted on the gimbal assembly. I can turn it a little. AND by doing that I have reduced the 'dead space' from 2/3 of the 1 scale mark to 1/5 of the 1st scale mark. Looks like it does have something to do with how the pot is mounted. but looking at Flaps30's pic of how the pot is fixed by 3 little metal tab, I guess I need to take the whole thing apart and drill all 3 holes a little to do that. I figure now there is only 1/5 of a scale mark, I think I might as well leave it alone before I do any futher damage. I am not sure 1/5 of a scale mark is worth the effort cause it is at the very end of the THR movement. and the sensitivity is probably only increased by 1/15. May be that is beyond my finger sensitivity any way.

[Flaps 30]

There is only one locating tab. That is the sticky outy shiny bit that you see in the picture of the potentiometer. It locates in the top hole that you see on the gimbal mount as shown.

Both of my transmitters have a small dead band (up to half a scale mark) on every axis at one or both ends of travel. So I would guess that this is the same for most people.

[kaos]

Actually, between my 2 Turnigy 9X , this throttle bottom stick is the only has a 'dead space' all the others for both gimbals are perfect. I have a 3rd T9X but it is still on stock FW. I don't know about that one.

Just a thought, it seems to me I did hear a lot about these potentiator issue but most are Flysky. I wonder if Turnigy 9x is using different oem potentiator. I sort of feel may be the Turnigy9x has a little better quality overall from what I read about these issues.

[kaos]

Must be jinxed by this thread.
flying my Q-bot micro in the the house, trying to catch it with one hand and oops my Tx slipped off my hand (ofcourse, it would happen on the few times I did not use a neck strap ) and dropped my Sky9X Tx on the floor. broke both THR and RUD switch. Scrambled to find replacement cause I am going to a local fly club tomorrow. Remembe I have an Racon Tx(a 6ch dip switch Tx came with my RFT erazor long time ago) no longer using and the DX4e Tx ( which I stripped out the tx module), between these two got one long and one short switch to replace the broken ones. Hew, they are working again.
switches are not as picky as pontiator. Actually, they all have the same spec engraved on the switch, 3A AC, 2A DC.

[ShowMaster]

So a friend of mine used my tx as a buddy box setup and insisted he use his trusted neck strap he has to fly with. The neck strap clip broke and my tx crashed to the ground breaking off the antenna and two switches. Him being technically challenged the repair was up to me. Like you I scrounged switches and a spare Frsky antenna and I was good to go but lost a good day of flying. I'm not sure weather to ban him from using my tx again or just his new neck strap?
I'm happy you and I could fix our TX's and got back into the air fast again. What would a Spektrum or Futaba owner do?
SM


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[Flaps 30]

switches are not as picky as pontiator. Actually, they all have the same spec engraved on the switch, 3A AC, 2A DC.

Most switches swing both ways (AC/DC) but there are ones that prefer it one way or the other.

[kaos]

Is there a difference between a AC or DC switch? I thought a switch is a switch, may be the current load is different.

[ShowMaster]

I looked it up to be factual.
IMO
AC 60 cycles/sec switches the voltage off 120 times/sec as it cross zero volts. This means the switch contacts have a good chance they're switching zero volts on or off when you hit the switch. This allows for smaller switch contact area and higher voltage to be switched.
When you switch DC it's duty cycle is usually 100% on and the contact area being smaller can't handle the current In rush as it did with AC's duty cycle.
AC only switches are less expensive, DC specific switches can be expensive.
So for our hobby needs being usually DC or data, use the DC rating number and enjoy. If switching large DC inductive loads some contact suppression should be added across the inductor (relay) or switch.
That spark you see and hear when connecting you're esc deans plug to your lipo also happens in a switch. It can slowly destroy the contacts and make them intermittent. That's one if the reasons to use slide and not toggle switches on our planes. The other reason is vibration. The slide switch wipes the contacts and keeps them clean and is a larger surface area. The toggle is a pressure contact held by a spring and usually a small surface area.




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[kaos]

that makes sense.

[ShowMaster]

For our tx use, if it fits it'll work.


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[jhsa]

Or you can control the gate of a FET with a small switch to drive higher currents.. Actually I'm thinking of building something like that for my IC planes.. But must be carefully tested of course

João

[ShowMaster]

I can see the Jhsa of the future

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[jhsa]

Hey, I want one of those

João