View Full Version : MR03S will not go

2015.06.19, 12:09 PM
Hello, this is my first post. :D

I'm trying to figure out options for fixing an MR-03S. The car was being driven without the body and rammed into the cat bowl, and water splashed onto the front of the chassis. Since then, intermittently, the power to the motor has been going in and out. The steering servo works without fail, but for about 2 weeks, it wouldn't work at first when you turned it on, but you could always get it to come back. Now...not the case. You power it up, turn the wheel left and right, that's still fine, but when you squeeze the throttle, nothing.

It just seems odd to me that the board gets power and the receiver and steering work, but not the 2nd channel. Is it possible that replacing the FET would fix it? Also, the MR-03S seems to only have 1 FET on the board, I thought they all had 2? Everything I see about FETs is 2x2 and 3x2. I was surprised to find that it only had 1 under the cover. If this is feasible (and even if only out of curiosity) which FET would be recommended for the MR03S, and how many? Can you stack single FETs?

I have SO many questions, but I will try to stay on topic...

I've been looking around for other options, and found the RA29 RC Unit set for the MR-03S, but if you spend that much, should you just do the brushless upgrade? Would the brushless upgrade even work with the KT-19 radio?

I'd like to fix it if possible. I'm hoping for the best here. Can anyone help?

2015.06.19, 06:28 PM
Quick answer on the upgrade, you would need to buy a new transmitter. VE run on the ASF And MHS system vs FHS for sports series. This makes the upgrade pathway less cost effective.

2015.06.20, 03:43 AM
Did you try the standard troubleshooting things first,
Replaced the motor, or just measure if you get any voltage while hitting the throttle. Maybe some water also got into the motor and it rusted or something.
Have you tried a different radio. Maybe the problem has nothing to do with you hitting the cat bowl (lol btw).
Have you opened up the cover? Make sure there are no false contacts anywhere. Try it when opened up.
Do you see any burn marks on the fets?

Good luck.

2015.06.23, 02:34 PM
Thanks for the replies.

Arch, good to know...that's what I suspected.

LED, actually, the car in question isn't mine. It's a coworker's MR03S. He did it at his house. I was trying to help, because I need someone to race.:D

Me and 2 other guys in my office have recently bought Mini Z's and race them in the vacant office next door. No real track, we usually just throw down a couple of sets of car keys or something and race around them in a long oval. There's the MR03S I mentioned, my MA020S, and the other guy has 2 MR-01's.

Over the weekend, he noticed that he could get it to come back by pressing down on the cover (opposite the antenna) so something is loose. He opened the cover and gave it a shot of duster and so far, it is working. He said he didn't notice any broken connection, so he just closed it back up and it's working now.

I'm sure it will rear its head again.