Tail servo twitch - what to do?

[James A]

Wow it's been a long time since I started a new thread, anyway after rebuilding my Trex 450 from a bit of a crash I noticed that the esc was getting hot (hotter than I remember) and so was the tail servo. So I looked at it more closely moving it left to right and suddenly found it starts to twitch when I get the angle just right (or wrong if you think that way). I tried turning the gyro gain down to nothing but it made no difference and then plugged it straight into the receiver.

Like I say, it's not across the full travel range, just at one particular spot but the twitch is very noticeable when looking at the tail and really will be knocking the tail off. It's a DS420 tail servo and normally connects through a gp780 gyro.

Any ideas as to what may cure the issue or is it simply a dying servo?

[snotvis]

Have exactly the same on my 250 - makes it a dog to fly. Gonna open the servo up and have a look at the gears. Maybe a slight stripping issue. If that isn't the fault, I am going to get a new tail servo. But watching this thread in anticipation...

[James A]

Well, I chatted to a couple of guys down at my local club and they came up with what I suspected, that it was basically a problem with the pot having a flat spot or something and not to fly with it which is probably good advice. I may rip it apart just to check it over as I'll have to order another anyway. Shame no one else appeared to have had the issue with a cure.

[cjcj1949]

You should be able to use any servo on the tail. I use a DS520 as it came with a rubbish Align Gyro. I've also used the rubbish 1kg £6 servos that come with the Twister Storm/ Blade 400. So long as you swop the gyro mode to analogue it will work reasonably ok until you get another good servo. If you can get to the pot you can replace it and if you can get inside it can be fixed by coating the track with vaseline. Something we used to do a long time ago. I don't know why it works but I know it did.

[1chris]

Since when have align giro's been rubbish?

[cjcj1949]

It was a RCE600. Drifted all over the place. That was before they integrated the temperature sensor with the rate sensor. It was about 3 years ago.

[snotvis]

Since when have align giro's been rubbish?

Had a GP780 on my Trex 500, struggled for ages to get it sorted...Replaced it with a Spartan and all was good within minutes.

[James A]

Had a GP780 on my Trex 500, struggled for ages to get it sorted...Replaced it with a Spartan and all was good within minutes.

Also have the GP780 on my Trex 500 and was not very happy with it for a long time but decided to strap it down the other day and that made some difference removing much of the wag. I then thought I'd actually move it to the recommended spot on top of the boom mount and it now holds really well. Still need to play a little more but have gone from thinking I'll replace it with a spartan to I'll wait until I decide to go flybarless (should I decide to do that). Anyway I'm hoping when the 450 is back in the air a little strapping on its 780 will remove the wag there.

I was going to simply replace the servo with a DS425 which is the replacement for the DS420. Anyone every used them? The one benefit is at £17 they're cheep.