Just bought a used trex 500 and this thing has a electronic gizmo on the side of the frame that I have never seen before. Please, if someone knows what this is... Let me know. Thanks, Jeff

Looks like a BEC. Kind of like the Parkbec, but looks a little differnet. Like a clone, or has been recovered, or a different vintage than mine.

Is it in line with the bec coming from the speed control ? Possibly changes a linear bec built into speed control to a switching style bec ?

Looks like it's a clone of the Western Robotics Hercules Bec. http://www.amainhobbies.com/product_...EC-44-53-6-83V

Well the ESC is a RCE BL70G. Supposedly to have a internal BEC? Online manual says it a 5-6V step-less BEC. The gizmo is hooked up in between the ESC throttle wire to receiver. Do I really need this thing, or is the internal BEC enough? I am running HS82mg servos on cyclic and a Futaba S9254 tail servo. Gy401 gyro.... Please any help will be greatly appreciated as it has been some time since I've been into helis. Regards, Jeff

I lot of people don't trust internal becs. And I mean a lot. I have had some fail, but not enough to make me not use them.

So, do I need to use that and what voltage should I set the BEC to?

Well they have disabled the bec in the speed control to use this or at least should have. I think if you follow all the wires you will find the red wire disconnected from the speed control to the RX.
I am a hands on kind of person and we are only 3 hours away lol!

The ESC is plugged into this thing, and it's power is hooked up directly to the ESC battery connection wires... Then the wires coming out the other side go to the receiver... This just makes no sense if the ESC has a BEC built in. Why the heck is this even there???!!!

If the BEC built-in to the ESC is not a switching BEC, i.e; linear, then there can be problems with running four digital servos off it. Especially for those of us who run Spektrum receivers, it was just cheap insurance to purchase and hook up a switching BEC rated high enough to run all of the electronics without running the risk of a voltage drop, which would cause the older Spektrum receivers to reset. Recovery would take 3-5 seconds, which was more than enough time to drive your heli into the ground. I believe most built-in BEC's are switching now instead of linear so there would be no need. However, since it's already hooked up, it surely won't hurt anything to leave it there. I'm running external BEC's on all my 450 and 550 helis, and will probably put one on the 500 I'm currently putting together as it will be going into a scale ship, and I don't want to take any chances with that. YMMV.

Edit: Just looked at the manual for the ESC, and it is a switching BEC rated for 3Amps continuous and 5 amps burst, so it should have been fine. With a linear BEC, as you moved to bigger batteries the efficiency would drop off dramatically above 3s lipos. Switching BEC doesn't have that limitation.

The ParkBec is designed so that the red wire can be hooked up. No need to disconect it. really you should pull it off to see if it has a label. The ESC's built in one is likely to be a better BEC. However he might have put it in due to issues with the esc's BEC.

Just found out its a Dimension Engineering sport BEC. I guess my problem now is the question WHY is there not a separate battery to power the servos???? The way it's hooked up just seems moot to me...

The Sport BEC from Dimension is a great BEC. I have two of them. As far as answering "WHY no separate battery?" I can't answer. But I don't run a separate battery either. Never have had a problem powering servos, gyro, etc.

One reason to not use a separate battery, If something go's wrong with the power system the heli will come down. If you use separate power and have a problem you could just sit back and watch your heli fly away!