I'm stumped! I've got 2 Dragonflies of my own and have had no problem repairing them. Now I've got one to repair for a customer and I can't figure it out.

It's gone through 2 of the mixer boards in about as many flights; no throttle or tail rotor control. Replace board, all is fine. Tried different Rx then Tx first, no effect. Definitely the boards failing.

After replacing the 2nd board it seems to lose tail rotor authority after a minute or so in hover. Both of mine did the same thing (motor was failing when hot, replacing tail motors fixed them). I replaced the tail motor on this one and it still does the same thing (loses tail rotor). Gyro gain is cranked all the way up.

Any ideas? Has anyone had new tail motors go "bad" right away?

Tony Pacini
Valley Hobby Shop

If you're using the GWS 3in1 mixing board, that is most certainly the culprit. The PHA-01 board is just awful, it constantly has problems. The FETS for the ESC's are located right beneath the gyro on the board, and as they heat up, they also heat up the gyro, causing really bizzare tail control, random tail movement, and the tail even spinning while the main blades are completely stopped and the helicopter is staitionary on the ground. During flight, the system constantly requires trimming to compensate for the 3in1 as the gyro heats up. Eventually you run out of rudder trim and need to land to let it cool down before flying again.

If you're not using the 3in1 board, then your problem is rather bizzare, I would guess something to do with the ESC for the tail, possibly supplying to much, or not enough, voltage. Or maybe there's just a loose connection somewhere. I've seen wires (especially if they're cheap ones) fatigue off after extensive use, coming seperate from PCB's and the like. Maybe someone else will have some brighter ideas. I had gotten fed up with the GWS 3in1 board and replaced it with a cheaper Walkera 4in1 and have had no problems since.

Yes, I'm using the GWS PHA-01 3-in-1 mixer. I've never heard of the Walkera model. Where can I find one?

In all practical aspects, the Walkera 4in1 is cheaper in quality than the GWS one, but it works alot better.

Unfortunately, to use the receiver, as far as i'm aware, it uses propieraty technology, and so will only work with a Walkera transmitter. It was an easy fix for me since I already had a Walkera TX from my original Walkera #4 Dragonfly. It also has no gain or mix adjustments, so if you get wagging on your tail, well, theres not a whole lot you can do about it.

I would suggest looking at either getting a seperate gyro/mixer/speed control setup, or look into the 3in1's made by other companies. You can also try contacting GWS, maybe they'll send you a replacement, maybe they've fixed the problem, I don't know. I'm usually very happy with GWS products, but their 3in1 is just terrible. Helihobby carries a few 3in1 boards from other companies, they're not as cheap as the GWS 3in1, but i'm sure they work a whole lot better.

If you're still interested in the route I used with a Walkera 4in1, any online parts retailer who carries parts of the Walkera #4 Dragonfly should have the 4in1 box. It's usually about $30 USD I think. You could also buy the Transmitter for $30. www.rc-expert.com carries them, but they're a bit slow on the shipping. I usually get mine from various sellers on ebay.

I think it is unlikely two boards are bad. I would keep checking for a short because I think that is the issue.

Carefully examine all of your wires and double check the polarity of all your connections.

Check your connectors too, because jst's are junk and they could be a problem too.

Check to see if your servos are in good shape.

Swap in a new main motor too for now until you figure this out.

I have shorted a couple of boards. Once it was the diode on the tail motor took a crash hit and the board fried on the spot. (So it is good you changed the tail). Another time, it turned out I had a bad servo, which caused the board to overheat. I lost one board before I figured out it was the servo that was going. (I was ready to lose it, then I noticed one of the servos was jammed/stiff and was difficult to move manually.) Of course this was the last thing I checked... doh.. Oh yes, make sure you have the polarity correct on your wires. For example, the motor wire should have the red facing out where it plugs into the board. It is easy to reverse this. Just take it one step at a time and you should be able to nail it.

As you test, see if the Board starts getting hot, and if it does, unplug and let it cool down, and keep looking for a short. Lastly, I assume you are not using a 3 cell lipo.. as this is too much for this board.

I do not think the pha-01 is bad. It is alittle delicate, but it works. It will cook however, if there is a short somewhere.

There are some of these boards that do work well. But it seems like the majority of people who use them have alot of problems with them. I've seen huge threads running on other forums about these boards. Ones in which Mr. Lin (the CEO of GWS) commented on the boards, acknowleding the problems..

Seems like a hit and miss issue, maybe it varies with the quality of components that go into each batch, as certainly, not all electronics are created equally, even from the same batch.

Sort of like baking cookies, some are cooked just right, and some are...well.. not so good

Wouldn't a short or reversed polarity show up immediately? It hovers fine for the first 30-45 seconds then loses tail rotor authority. I've had this happen with both of my Dragonflies and replacing the tail motor fixed them (replacing it on this one did not).

I'm stumped!

No, I am not convinced that problems appears instantly. In fact, when I was having problems with the sevo that was causing things to overheat, it took a little time .. , which gives you enough time to unplug things before it fried.

yes, when I had the crash and smashed the diode on the tail, that was immediate death.

I would check again and see if the servos etc are working right.
That's my 2 cents.

If there was a short the helicopter would not take off at all. The ESC would get hot very quickly and likely not respond to any command given to it. He certainly would not be able to hover around.

I think you need to look elsewhere for your problems. Try swapping your main motor and see if that solves anything. Wierder things have worked .

It may be worth noting, that if, as you said, the helicopter works for a short period of time and then the tail simply gives out, it could imply a problem with the tail motor, or the tail ESC on the 3in1 board. Next time you fly it, touch the 3in1 and see if it's even remotely warm in any areas. I'm not sure if the GWS onboard ESC's have auto-shutoff in the events of overheating, but it would be a likely culprit. In which case, it could simply be a bad motor, bad wiring, bad soldering, or something as simple as a wire that's had it's insulation cut off somewhere and happens to touch something metallic during flight. Also check to see if your tail motor is running hot at all. If you're running the gear drive tail, check the meshing to make sure it's not binding during flight and overloading the ESC.

Or, you could have a bad 3in1