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Hitec 81

Servo twitch

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Maurice Dyer09/01/2020 16:52:40
61 forum posts

Hi

Got an hi te c 81 mini in a futab a fund R2006gs. When I switch on, one servo judders, but then settles down when I waggle it. Dirty track of ??. How do I fix it ??

Maurice

RC Plane Flyer09/01/2020 16:57:15
675 forum posts
19 photos

My experience of the Hitec 81 servos was very poor. Great servo from new but any knock on the area being operated by the servo and it was a time to take out strip down and new gear set. Would suggest you invest in a another servo

Piers Bowlan09/01/2020 17:09:45
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1993 forum posts
53 photos

I think the HS81 has a plain bearing and plastic gears and it is a budget servo. You could try stripping it down and see if any gear teeth are missing. If so, you can probably get spare gear sets from eBay if you can be bothered. You could try spraying the potentiometer inside with electrical cleaner but the cleaner may cost more than a new servo - and not make any difference!

I have bought quite a few Corona DS-929MG servos from HobbyKing, if you think of getting a replacement servo.yes

 

Edited By Piers Bowlan on 09/01/2020 17:14:58

Nigel R09/01/2020 17:42:07
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3398 forum posts
524 photos

"When I switch on, one servo judders, but then settles down when I waggle it."

Does it continue juddering at the centre, after you have waggled it?

Maurice Dyer09/01/2020 23:21:15
61 forum posts
Posted by Nigel R on 09/01/2020 17:42:07:

"When I switch on, one servo judders, but then settles down when I waggle it."

Does it continue juddering at the centre, after you have waggled it?

No sir, it settles down.

Maury

Piers Bowlan10/01/2020 14:58:23
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1993 forum posts
53 photos

When you move the servo full travel to full travel, does it do so in a smooth, linear fashion or does it sometimes jerk or hesitate before continuing? Also is it noisy compared with it's stable mate?

extra slim10/01/2020 15:21:05
459 forum posts
48 photos

Sadly I echo what has already been said, and I have confined HS81's to the throttle if at all, and agree that the corona are far better. There will be plenty of people with good HS81's, but especially over the last few years, I have had issues with HS82MG's (poor centering) and HS5245MG's (also poor centering)... and only the HS85MG's seems to be of the expected standard in the midi hitec range, especially bad when the so called budget brands have upped their game. I personally wouldnt try and repair it for what it would cost for a decent corona.

Andy Stephenson10/01/2020 16:50:31
41 forum posts
1 photos

HS 81 servos don't play well Futaba receivers at switch-on. I find they jitter until I move the sticks, then they are perfectly OK. It's something in the way the servo perceives the power-up and control pulse at the same time. I have noticed this going back to 35MHz PCM receivers but never had a problem flying those servos.

A.

Martin McIntosh10/01/2020 20:33:15
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3078 forum posts
1119 photos

I do have a few of the HS 81 and 82 series but when buying new at that size I would always go for the Corona ones. Huge range of them, great price and so far very reliable.

Maurice Dyer13/01/2020 07:45:33
61 forum posts
Posted by Nigel R on 09/01/2020 17:42:07:

"When I switch on, one servo judders, but then settles down when I waggle it."

Does it continue juddering at the centre, after you have waggled it?

Sorry for the delay.

No, it settles down and works ok ??

Maurice

Andrew Ray13/01/2020 08:01:16
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743 forum posts
19 photos

Have you tried this servo in a different receiver output or a different servo in this output? Just to prove if the problem is the servo and not something else.

If a different servo doesn't display the same symptoms you can be sure it is the HS81 servo and then the best advice is just to replace the servo.

Edited By Andrew Ray on 13/01/2020 08:04:20

Andrew Ray13/01/2020 08:02:03
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743 forum posts
19 photos

Edit

Edited By Andrew Ray on 13/01/2020 08:03:22

Nigel R13/01/2020 09:30:36
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3398 forum posts
524 photos
Posted by Maurice Dyer on 13/01/2020 07:45:33:

No, it settles down and works ok ??

Maurice

If I'm honest, I'd probably just live with it, if it is really only something that happens at power on and goes away after a quick waggle of the sticks.

HS-85MG are all round much better than the 81.

If you're looking at corona 929 then the HS-65MG is a far closer comparison in terms of size / weight / torque, I think.

The 81 are good enough in low load (throttles, small surfaces / slow flyers) type use, although the 82MG version has obviously more resilience to knocks and bumps.

Martin McIntosh13/01/2020 10:55:38
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3078 forum posts
1119 photos

Try disconnecting the other servos and see what happens, some are not compatible with 6V and although they seem to work fine can affect the others.

Does this only happen after a fresh charge? If so ignore it.

The problem is often due to a dirty or worn pot. Also, Hitec use a sprung connection to the pot. centre, not a wire to a wiper. This can get dirty or corroded and can be checked by applying a very small dab of WD40.

To be quite honest, for all these cost, you may as well just replace it.

Nigel R13/01/2020 14:16:07
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3398 forum posts
524 photos

Should be ok on 6v, according to Hitec website.

Andy Stephenson13/01/2020 15:37:54
41 forum posts
1 photos

There's nothing basically wrong with HS81s that twitch only on switch-on, providing they don't continue to after the sticks are moved. It's entirely a power-up issue.

Maurice Dyer13/01/2020 16:34:23
61 forum posts

I had made up my mind to live with it and not make a mountain out of etc.I

I was trialling the aileron installation and movements before covering and painting, but the servos were just laying loose on the bench. So, I installed them properly and guess what ?. Not a twitch.

Dipstick or what. Thanks for all the answers, and advice. Forty years a radio flyer, and still a dipstick.

No hope I'm afraid..........

Maurice

Nigel R13/01/2020 16:38:57
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3398 forum posts
524 photos

Perhaps Hitec have tweaked the servo's electrics to expect a small amount of load (as in, driving an actual surface).

"Dipstick or what"

Nope - no such thing as stupid questions, etc.

Happy ending I would say

Martin McIntosh13/01/2020 18:28:59
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3078 forum posts
1119 photos

No problem Maurice, we are all here to help each other. Better to be safe than sorry. I have had similar issues resolved on this forum.

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