250 DFC PLUS: Potential 3GX MRS issue

[spykez]

So, I smashed my BTF (MRS) recently and I could not get local supply of 415's/gears in a hurry.

So I thought to myself, ok, I've got some eflite DS76's. I'll use them.

So this morning, I dig through the parts bin and as I am doing so I get this "sinking" feeling that it's not gonna work. Spykez, me boy, I says to myself, why the hell not? Some of the lads here use 'em....

Then it dawned on me....

The MRS setup is so rudimentary... There is no BX equivalent setup I step.

How the $@&@$! am I going to reverse any of the servo vectors on this unit? I can't reprogram my DS76's if the directions are wrong.

So now here I sit, staring at my disassembled 250, cursing....

I could take a punt and try and mount these elites, but honestly, I see no way I can reverse any of the cyclic servos if they turn out to be wrong. So they still sit and wait in their packaging.

Have I missed something bloody obvious here? Thanks, gents!

[Robcol]

When I changed servos I'm my 250 plus and the servos were not going in the right direction I had to reverse them in my Tx.

[spykez]

Thanks but the servos on the BTF MRS are under the control of the FBL gyro and not the radio.

I can reverse cyclic or collective on the radio, yes, but that's one level above the ccpm the FBL unit does. The servo setup on this unit is extremely limited. Also, I cannot alter the gyro correction bar that of the tail.

I am trying a workaround today though.

I noticed the servo slots cut in the frame allow the elevator servo to be physically reversed. As in, you just mount it upside down in the other slot.

Now, the aux and the aileron servos can be reversed as well, but INCLUSIVELY, by swapping slots and inverting.

So whether this works would appear to depend on the directions the front cyclics will have. If they play ball, I'm good to go...

[spykez]

Gah! The cyclics won't play ball.

I can physically reverse the ele servo by relocating it and see it correct correctly but not the two forward cyclics.

I could flip the gyro upside down and reverse the radio aileron and fix up the ele servo like I said, but that means the pots are inaccessible.

Unless I know how to reverse the servos physically or reverse the servos and/or maybe correction for the swash, ON THE GYRO, that's it for the MRS and the DS76's.

Looks like they intended the MRS to be used with their own servos only (or at least servos with similar orientation). This is something they don't tell you, lol. I might ask in the align FBL forum, I might be missing something, that said. Maybe I'm jumping the gun.

Ah well, my resupply should be arriving tomorrow, chuck in a vortex and all will be grand.

[Murph_d]

I was never able to get the 3GX-MRS to work with DS76 servos, but I really wanted to use the servos (for the weight savings), so I ended up using a different FBL controller (AR7200BX)

[spykez]

Since I need to brush up on soldering (and have been known to be just bloody minded), I gonna try and reverse a DS76 electronically.


Wish me luck lol... And hope my resupply package (vortex etc) comes today!