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View Full Version : KT-18 steering pot?


ChiMiniRc
2011.03.22, 03:41 PM
I have over a dozen of these radio's and am up to 3 now that the steering pot is shot. When you turn the wheel FULLY to the left, the wheels jump to the right. When reading the resistance on a meter, you see the number jump around with readings right at the pot.

Anyone able to successfully get spares? I hear this is common. I've contacted Kyosho of America who says they get the radio OEM from KO Propo. I've contact KO Propo who says they only source the boards. The assembly and pots is sourced by Kyosho.

I did an online search for the number on the pot and came up with nothing.

Guinness
2011.03.22, 04:01 PM
For the past 2 weeks or so, I've noticed my kt-18 has been doing this too and it does it on the same side as yours (when i turn left, it jumps right). I had no idea what was wrong til i read your post above. I thought it was just interference but i had a feeling something was wrong.

at the track, i go into the wall 8 out of 10 times on a certain left turn...very frustrating, but at least i know why it was happening now

hopefully someone can help

ChiMiniRc
2011.03.22, 04:32 PM
One thing that just came us is potentially the pot is getting torqued and the fingers that contact the carbon pad are lifting away. Perhaps bending them down a little for more pressure may help. Or adding some material to the wheels to act as a stop for the wheel.

I'll let you know what I try out. I can say I've tried Deox-it cleaner and deox-it gold and no change at all. So I'm pretty sure it isn't a cleaning issue.

wildthing
2011.03.22, 06:00 PM
is it a 5K ohm potentiometer? is it a metal case or black plastic type?

you can hack a cheap standard size servo (like the futaba)... they usually use a the 5K ohm metal potentiometer.

as for the black plastic type, the nearest hack would be to use a bourns potentiometer with a 5K ohm value (bourns comes in several shapes and sizes, and there is one that might be similar to the stock).

ChiMiniRc
2011.03.22, 06:07 PM
is it a 5K ohm potentiometer? is it a metal case or black plastic type?

you can hack a cheap standard size servo (like the futaba)... they usually use a the 5K ohm metal potentiometer.

as for the black plastic type, the nearest hack would be to use a bourns potentiometer with a 5K ohm value (bourns comes in several shapes and sizes, and there is one that might be similar to the stock).

Last I remember it was metal. I'll get pics up.

herman
2011.03.23, 12:23 AM
have my kt-18 for a pretty long time - don't really do any racing.... and haven't had any type of this thing happening...

can you post pics and probably a video to help me (and possibly others) understand what's happening?

from your post... when you turn it fully to the left the wheels will suddenly veer off to the right?

my guess is that the feedback from the steering wheel has gone past its limit (max left turn) and thus it senses that it must go back to the opposite side, in this case right...

does the same thing happen if you turn the steering wheel full right?

ChiMiniRc
2011.03.23, 09:12 AM
have my kt-18 for a pretty long time - don't really do any racing.... and haven't had any type of this thing happening...

can you post pics and probably a video to help me (and possibly others) understand what's happening?

from your post... when you turn it fully to the left the wheels will suddenly veer off to the right?

my guess is that the feedback from the steering wheel has gone past its limit (max left turn) and thus it senses that it must go back to the opposite side, in this case right...

does the same thing happen if you turn the steering wheel full right?
For the 3 radios I have that have the problem, it's always full left. If you start full right, and slowly move the radio to the left, the wheels turn as you would expect. Just as you reach full left, the steering jumps to full right. And if you back off every so slightly, it goes back to left. You can play within this fraction of an inch a full left turn and bounch the steering to full throw right and left.

Guinness
2011.03.23, 10:25 AM
after playing around with mine last night, i noticed:

-when it's full left, my car's wheels don't turn or jump right as i first thought. they either stay neutral or flicker between neutral and left jumping back and forth as full left is held solid. this causes the car to go erratic.

-it happens on all my cars (MR02/MR03/MR015) but not with my Dnano...so far. Didn't get a chance to check it with my AWD yet.

Guinness
2011.04.05, 12:37 PM
ChiMiniRc, did you ever figure anything out?

i'm probably going to upgrade to a better radio, but i'd still like to fix this. might take it apart this weekend and see what happens

herman
2011.04.06, 02:04 AM
yeah wondering if there are any solutions to your problem...

chiminirc... are the three kt-18's used for you rental cars?
if so maybe the users are too rough on them...

haven't actually opened mine up... but your statement below makes some sense...

"One thing that just came us is potentially the pot is getting torqued and the fingers that contact the carbon pad are lifting away. Perhaps bending them down a little for more pressure may help. Or adding some material to the wheels to act as a stop for the wheel."

ChiMiniRc
2011.04.07, 11:07 AM
chiminirc... are the three kt-18's used for you rental cars?
if so maybe the users are too rough on them...



The club doesn't really do rentals so much as provides cars as part of the membership dues (there is no upcharge for a car). Are they part of this fleet? Yes. Are they used extensively? No.

Esentially all the 2.4ghz cars are Mr-02's and MR-03's with the PN 70t motor. This only ends up in the hands of experienced drivers and most of those folks have gone on to buy their own cars. Within the club, these failing radios haven'y been used more than 6 times. It is also unlikely one of the users would have gone nuts torqueing the wheel over.

At the same time, many racers pretty much steer full lock and our events run for 4 hours with all of us running the entire time. So maybe 20-24 hours on the radios?

Overall, I'd say premature and unlikely caused by ABUSE. That's for the AM radios which have seen there fair share of pure hell and have held up like champs.

PS. the battery release and the power button are too close to each other on the KT-18. I've had my share of people unfamiliar with the radio release the batteries onto the ground a few times.

UVE
2011.10.26, 08:48 AM
Any follow up?I got the same problem.

Rune
2011.10.26, 09:35 AM
We have had the same problem on about 4 radios here also.

The simple solution is to limit the travel with a spacer on the plastick end stop on the radio.
Just glue it on and it works forever.

Roughly 1 mm has done the trick here.

It will not limit steering travel on the car at all.

I-Lap
2011.10.26, 11:32 AM
We opened one up and checked this out one race day. It is not a mechanical defect or breakage or wear.
It appears to be a calibration issue. When the pot signal voltage drops below a certain point, it rolls to the extreme full opposite if the center calibration is off. There should have been a check in the firmware to prevent this.

Anyway, to make a long story short, after I discovered the above, we did two resets back to back and then it was fine.
To reset, hold down throttle trim while powering on and hold until it beeps. Make sure the steering wheel and trigger are centered while doing this.

Please post back any results.

Cherub1m
2011.10.26, 12:49 PM
Nice info guys, just wondering if someone wanted to replace/change the steering and/or the throttle pot does anyone know where we could get them? I replaced one of my Kt-18 throttle pot(with old futaba radio) it works great its just to big, had to expose part of the pot through the back of the radio. Basically I would like to know where to get one that is an exact replica or fits well.

wildthing
2011.10.26, 07:31 PM
@cherub1m, you need to unsolder the pot and measure the resistance of the two end plugs. If it just like the typical tx, it will be a 5kilohm potentiometer.

Try to browse on line electronic parts sellers and see if they got those - example digikey http://www.digikey.com/

UVE
2011.10.27, 03:41 AM
We opened one up and checked this out one race day. It is not a mechanical defect or breakage or wear.
It appears to be a calibration issue. When the pot signal voltage drops below a certain point, it rolls to the extreme full opposite if the center calibration is off. There should have been a check in the firmware to prevent this.

Anyway, to make a long story short, after I discovered the above, we did two resets back to back and then it was fine.
To reset, hold down throttle trim while powering on and hold until it beeps. Make sure the steering wheel and trigger are centered while doing this.

Please post back any results.

Yes,it fix the problem after I reset,thanks for your info.

Cherub1m
2011.10.29, 11:55 AM
@cherub1m, you need to unsolder the pot and measure the resistance of the two end plugs. If it just like the typical tx, it will be a 5kilohm potentiometer.

Try to browse on line electronic parts sellers and see if they got those - example digikey http://www.digikey.com/

Thanks wildthing, I'll try them (I think I have something that can measure resistance). I've actually used digikey for Fets before not sure why I didn't think about them for this :D I guess it goes back to this "Jim...I am a Doctor not an Electrical Engineer" :D

civilian
2011.11.01, 02:45 PM
happens all the time at all aspect...
why people try to solve thing using hard way?

change the pot?

already reset your TX yet?
wasting time when this problem happen you tear down your TX and replace the pot.

simply press the down trim button, hold and turn on your tx.
dont release the button untill it sounds as you turn it on normally.

many times that problem occurs to different racer here at my local track, we do the same thing and problem solved!

:D

chris130256
2011.12.10, 07:22 AM
Big thanks to I-Lap and Civilian for their info. I have 2 KT's I was going to throw away 'till I searched this thread. Now I've got 2 KT-18's that work perfectly.
Thanks again Guy's.:cool:

njd13
2012.06.16, 10:35 PM
Just checking in that I-lap's fix has worked for my kt-18. Try it first before taking your control apart.