View Full Version : RA-31 / MA-020 Sports receiver

2015.04.11, 12:20 PM
I bought a RA-31 receiver for the new MA-020 Sports AWD, to replace an AM board. I got a new ASF top cover and everything fits together fine, however I have an issue with the steering.

Initially, the servo motor wants to spin only one way, unless the pot is thrown all the way to one side. When the board was installed in the car, the steering would lock all the way to the left as soon as the car was turned on (after binding to my radio). I removed the board again and connected it only to the battery terminals and found I could stop the servo motor by turning the pot all the way to one side.

I then followed the steps to centre the chassis steering found in this thread (http://mini-zracer.com/forums/showthread.php?t=39628), but with the pot centred by eye.
After doing this, the servo motor will stop spinning with the pot centred, but then the servo motor only spins when the pot is thrown to one side of centre and not the other.

My radio is an EX-1UR with a FS-TM002 FlySky module. All settings are default, and throttle works. The same thing happens with the FS-TM002 connected to an Airtronics M8.

Does anyone have some hints as to what is going on?

If I can't get this sorted I will go back to AM, but the plan was to upgrade this car to FlySky 2.4GHz, and put the AM board into another Franken-roller. If I want to run both cars as AM, I will need to get another AM top cover.

2015.04.12, 01:06 AM
Wow, sounds pretty weird, almost like the pot is wired wrong. Will you be at the meet next Sunday(19th)? If so bring it with you and we'll take a look.

2015.04.12, 01:20 AM
I did try switching the pot wires around and it still seemed to have the same behaviour. The wires are all back to the way they were now. The AM board I am using now (RV Project/Atomic) came with the servo motor wires reversed, but this RA-31 is totally weird.

I am going to be out of town so I will miss the next meet, but I can bring the board over next time I can actually make it out. Thanks for the offer Steve!

2015.06.14, 11:26 PM
Update on the situation, I think the problem was that there were some crossed wires on the board, there might have been a tiny contact between one of the servo motor wires and one of the pot wires that was just barely visible, but whose existence was enough to cause these problems.

I resoldered the wires, additionally had to reverse both the servo pot wiring and the servo motor wires, and now the board works normally, bound to a TM-002 FlySky module. Very weird that the board would have had such QA issues straight from the factory.

Anyway, really hope I can have this machine out on the track at the next meet!

As an additional question, I only probed around the board a little bit but didn't really find a suitable power source for running auxiliary devices from the board. For now I have soldered two micro Deans connectors directly to the chassis battery terminals to run a Trackmate transponder and an ATtiny45-based LED controller, and while the Trackmate seems OK, my LEDs cut out whenever I give a burst of throttle.
I have a similar LED controller attached directly to the battery terminals of a MR-03 ASF chassis and the LEDs don't brown out like this...

edit: I added an inline 5V step-up/step-down regulator to my LED controller circuit and it seems to work fine now.