GY520/8700 problem

[Spanner]

So, the other day I bought a GY520 to replace my aging HH gryro, all went well, installed nicely. However I noticed that the Servo goes to the clockwise mechanical endstop when I power the Rx. Any ideas how to stop the gyro doing this? My old gyro didn't do this .

[ame="http://www.youtube.com/watch?v=JS89L3JylIM"]YouTube - JR8700g and Futaba GY520 problem[/ame]

[raptorheli2]

you can't fix this. the 8700 only works with a few gyros....the 520 is not one of them.

it happens because of the way the 8700 initialises. it needs a centre pulse or it goes hard over-futaba do not do this with their gyros at boot up.

you either need to buy another gyro or servo.

cheers

[Spanner]

Are you saying that it won't work, or I can't stop it from doing this? Because it all seems to work fine once its recovered from hitting the endstop. (not flown it yet, tomorrow it gets its first flight)

[raptorheli2]

i'm saying it will work but you will damage the servo because it binds and you can't stop it.

i would recommend you do not use it like that.

cheers

[Spanner]

Cheers bud, best get on the blower to Fastlads then!!

[raptorheli2]

if your getting another servo then the align ds650 seems to be a good value for money item and not heard any issues with it.

if your going to get another gyro the only ones i know which work with that servo are the spartan 760, quark, CSM 720 and JR gyros ofcourse. there maybe more but i don't know what they are.

cheers

[Spanner]

New servo I think chap, again, thanks for the input.

[Spanner]

shame they don't advertise what servos they don't/do work with.....

[raptorheli2]

spartan list all servos on their manuals/website.

i'm sure others do the same but again i don't know for sure.

the problem is the 8700 is not a digital servo, it is a super servo.

the binding problem is not only an 8700 problem, other JR servos also used to suffer this. in recent years JR have conformed to the rest of the market and now drive the servos from first boot.

cheers

[Spanner]

New servo ordered!

[Rotorhead]

Well, you've ordered another servo, but there is one way to get it to work while waiting, unplug the servo, turn on the power and wait for the gyro to initialise then plug the servo back in, it should work unless the gyro can detect that no servo is connected and refuse to initialise until there is, but I've never seen a gyro that does that, and I doubt the 520 would due to it supporting 760 pulse width, which would require having no servo plugged in to set that mode up.

[Spanner]

yeah, unplugging the servo works. Thanks

[Angelos]

You can't fix this. The 8700 goes full travel if the control signal is left idle at high state which is possibly what the gy520 outputs before if finishes calibration. We had the same issue with the ds760 when it was first launched but we were able to fix it via a firmware update.

-Angelos

[Spanner]

thanks for all the advice chaps. God I was up late last night!! (too much homebrew!)