700XN throttle servos failing!

[chrisleematt21]

I have a trex 700xn, it is/was using all the standard servos, I am using a vx1n fbl, it has a gryphon tiny booster on the glow plug and I am using a 2s RX pack along with an opti-guard backup battery. It also has a spartan Micro power bus and I am using JETI so have a JETI REX 3 on it. I am using the vx1n gov with a spektrum RPM sensor.

So far it / I have killed 3 of the standard throttle servos, all within the first 5 mins of their maiden flights. They just completely die as if they are no longer powered. I have now got a savox 1250mg hv which has done approx 30 flight and is starting to fail, I have taken this off the heli. It would be fine then stop working, then if moved by hand it would work again.

I have just ordered another servo which is a DS530m.

The end points are set correctly, its possible that they were not set correctly for the first one, but they were defiantly set correctly for the rest, after the first one failed I triple checked the end points for the other throttle servos.

I don't think the heli is vibrating any more than a nitro usually does.

I have spoken with Angelos at spartan and he really doesn't think its the VX1n.

I am running out of ideas and getting fed up with buying servos!

I tried a throttle spring with the savox servo for the first 3 flights but then took it off as the servo seemed to be getting hot (it was only 40 celius when checked, but felt hot)

Things to try that I can think of are:

1. Replace the fbl unit with another and see if it has the same issue
2. Enlarge the servo hole and fit a full size throttle servo instead of the mini one supplied with the kit.

Does anyone have any ideas what could be killing the servos?

[Guest]

That’s annoying. Strange it’s always the throttle servo. I’ve run mini on nitro and gasser with zero issues so it’s something in your setup.

Check the frequency is set correctly for the servo. You could drop the hz if it’s getting hot maybe set too high?
Voltage but if it’s a HV then should be fine,
Check for binding,
Failing that swap out the fbl unit.
in mini terms the MKS HV is very nice and for me ultra reliable.

MJ

[chrisleematt21]

Cheers maj, ill have a look at the mks.

The frequency is set to 1520 which i beleive is correct for these servos. The new one should arrive today so i think ill swap out the fbl tomorrow and see.

[bigpops]

1520 is the centre pulse, not the frequency.

The frequency is how many times per second the servo is sent a new position. On the Spartan, I think there's no option and it's always 333Hz, which should be okay for all digital servos. It's been a while since I had a Spartan, so I could be way off.

[waveydavey]

Make sure the throttle servo isn't set to be analogue.

[Rachel]

i had the same issues with a vx1n it was the gov gain too high, drop it and your issue should be fixed

[chrisleematt21]

i had the same issues with a vx1n it was the gov gain too high, drop it and your issue should be fixed

How does the gov gain kill the servo? Does it make it work to fast / hard?
Thanks

[chrisleematt21]

i had the same issues with a vx1n it was the gov gain too high, drop it and your issue should be fixed

How does the gov gain kill the servo? Does it make it work to fast / hard?


Thanks


Actually now you say that, i upped the gov gain by 5% about 2 flights before the last servo died! The default is 60, do you remember what you lowered yours too?

[Rachel]

How does the gov gain kill the servo? Does it make it work to fast / hard?


Thanks


Actually now you say that, i upped the gov gain by 5% about 2 flights before the last servo died! The default is 60, do you remember what you lowered yours too?

from memory 32 but i too had a load of servos fail, only on the throttle ,...dropped it , the gain and all was great .

[chrisleematt21]

FFS I have just had the DS530m fail on me

not very happy at all.

I think I will swap the vx1n with another vx1n and file out the hole and put a full size servo in it. I never had these issues on my previous nitros and really have no idea why it keeps happening.

The servo was not binding at all, it was nice and smooth the whole way, zero binding and stalling. everything is nice and smooth.

This servo was nice and cool to the touch.

I had lowered the gain to 35 from 60.

running out of ideas. I didn't have the throttle return spring on this servo