The following article is nothing more than a project report. I take no responsibility for how others may use this information.
There has been a decent amount of talk on the forums about the Spektrum AR6200 receivers failing when used on bigger helis. I have been using an AR6200 in my Protos for almost a year now with no problems and so when I got my new TRex 550e, I grabbed another. When I told others about my choice of rx, a few warned of problems and linked to a few threads on the issue. It would seem that the AR6200 uses a very small circuit trace as the power buss for the servos and it can fail when using full size digital servos. Intrigued, I took the AR6200 out of my 550e and opened it up. Sure enough they are using a single, very small trace to handle all the current needed by the servos, a current that can be in excess of 10A for short periods. So I thought why beef it up? And so I did and here is what I did.
Opening up the AR6200
I found this to be the hardest part of the whole project. Even being careful, I snapped off one of the little catches. I am pretty sure there is no perfect tool for this job. I used a little flat blade on my pocket knife and took my time. Once it is open, here is what I found.
Snapped off a catch ...
Taking the board out and flipping it over shows the trace that started me on this project.
That little trace has to handle all the current the servos use!
I have seen several photos of that small trace burned out. Knowing the pin-out for servos, I knew the left row of pins are the signal connections, the middle row is the V+ connection and the right row is the ground connection. My goal was to beef up both the V+ and ground rows.
Time to get the soldering iron out
Because I was working on factory made board, I re-remelted each solder joint I plan to work on and added a little of my own solder. This removes any oxidation or coverings on the solder joints and makes them much easier to deal with.
Melt each joint and add in a tiny bit of new solder to each.
Next up I prepared the wire used to beef up the bus. I used standard solid phone line wire. This is the same type of wire that comes in cat5 wire used for networking. It is 22awg I think. The wire is about the same size as the pins on the other side of the rx.
I started by stripping off the insulation on a few inches of the wire and then I tinned an inch or so of it.
Once I got the wire well tinned, I cleaned the tip of the soldering iron well and added a tiny bit of new solder. I placed the tinned wire exactly where I wanted it and melted the solder to connect it to the the first pin. I wasn't too worried about getting it perfect right away, I just wanted the wire to hold in place. Next I lightly soldered the wire to the last pin. Once I was happy with the position of the wire, I then went to the middle pin and worked my way out. I made sure not to hold the iron on the board too long, as I didn't want to hurt the board. My soldering philosophy is "get in and get out quick".
Once I had the middle row of pins is done to my liking, I clipped the end off the wire and got ready to do the other row. Below is the end result.
Testing the receiver
Once the mod was done, I double checked all the solder joints. I used a camera to get a nice clear macro shot of the end result and studied it for a minute on my computer. Everything looked good and solid, and most importantly clean. Next up was a range test. I used an extra bec and old servo. All checked out fine, but I was still careful on my first flight.
Was this mod worth the effort? The risk? Would I have been better off to just use the better AR7000 receiver instead? These are all questions that I asked myself but being a tinkerer, and I knew I could pull it off with a problem. In the end if this mod allows me to run the AR6200 receiver in my larger models without the fear of toasting a trace and causing a crash, then it was worth it.