MMP spektrum sr300 question.... - RC-Monster Forums

hootie7159 · **MMP spektrum sr300 question.... -** 05.06.2010, 11:47 PM

hey guys....quick question but first here's my setup:

hyper 10sc geared 42/14
novak 4.5 HV 5mm motor
mmp stock settings except (30% drag and 6.0v to BEC)
dx3e and sr300 tx/rx
s300 servo
running 2s 30C tunigy 5200mah lipos

my truck works fine and is perfect for the 1/10 scale track i run on and it hauls booty...however, i ran into an issue when i initially tried to run it...the power to the rx would cut out going from a dead stop to full throttle...i know its a bec problem but all i did was add a glitch buster (cap in the aux slot in the sr300) and it fixed the problem...Is this common with the mmp's? or do i need to send it in to get fixed?....it works fine with the power cap but has issues without the cap....

hootie7159 · 05.09.2010, 05:02 PM

Bueller?

simplechamp · 05.09.2010, 06:08 PM

If I remember right the stock punch control setting on the MMP is 0% (disabled) so you might be overtaxing the batteries when you hammer on the throttle, the pack voltages drop and the BEC shuts down momentarily. With the capacitor added it might be just enough to keep the system alive until the pack voltages stabilize and rise back up. So maybe try adding some punch control and remove the cap and test again. I could be totally off-base, but it seems possible to me.

simplechamp · 05.09.2010, 10:42 PM

Great, as soon as I reply to your thread I'm having my own BEC issue now with my new MMP. Just got all the connectors soldered up and ready to go today. Connect everything up, turn it on, try to test the steering, and the RX (SR300 also) is going out when I turn the wheels. The only way I can get the wheels to turn without shutting down the RX is go very slowly. Tried with two different servos and it does the same thing, and neither of them are particularly high power servos.

I might try a cap like you did and see if that helps, otherwise the question is do I send it back to Castle or just use an external BEC?

hootie7159 · 05.09.2010, 11:18 PM

Hahaha that sucks bro! Yeah the servo I'm using the the s300 that came with the dx3e...all I did was add the novak glitch buster cap thingamagig....I also boght another mmp for cheap but didn't have a chance to try it out...I'll let you know if the same thing happens to my backup mmp.....as for sending it in....if the ext cap doesn't work send it in for sure but for now I'm just happy that I can drive my 10sc now :)..although I may send it in if my backup mmp doesn't have the same issue..

simplechamp · 01:00 AM

I added two 680uF caps and sure enough that seemed to fix the problem, everything functions fine now just like in your situation. I'm starting to think it's more the receiver causing the issue than the MMP. Going to switch to a single 1500uF cap eventually, but the 680uF were all I had laying around.

hootie7159 · 05.10.2010, 01:04 AM

I ran the same reciever on a MMM/2200kv setup on 4s with a 5779tg and it worked fine then...???well ...at least we were able to somewhat remedy the problem for now

hootie7159 · 05.12.2010, 10:08 PM

well...the other mmp i have does the same thing...power cuts out on the rx under full throttle but does fine with a cap added to the rx....do i need to send both in? or do i have setup problems...?

simplechamp · 05.13.2010, 12:36 AM

Quote:

Originally Posted by hootie7159

do i need to send both in? or do i have setup problems...?

I'm debating the same thing. I don't think it's the setup, I think it's the BEC not handling the load. After researching a bit this seems to be a fairly common issue. Since I just got mine I'm going to run it for awhile and see how it behaves. Got plenty of time left on the warranty if I do decide to send it in. As long as everything works well with the cap I don't see any reason to send it in.

MikeW · 05.12.2010, 10:50 PM

I'm running the MMP without any problems on 5S and with a Tekin T8 motor.

It kinda chugs sometimes, very rarely, it almost is cogging like when given full tilt while fully steering at pretty low speed.

This was in my yard with a shitty FM radio, now with a 2.4Ghz setup no problems..... Try another radio and see if it makes a diff, maybe a AM radio you have laying around....

hootie7159 · 03:45 AM

damn...well, tonight i was just running it in my backyard doing a suuuper slow full lock left turn and then punching the throttle and it would still cut out (but not as long maybe 1/2 a second) but if running it at WOT and doing turns and jumps it would be fine...just when i did the full lock turn/throttle punch...and this was WITH the cap added....sooo, i changed the servo (went from the s300 spektrum 100oz/in servo to the stock ten-t servo 55oz/in) and the stall was gone without the cap :) .... so i thought it was a bad servo.....but then i put it on the ground and did the full lock/throttle punch test and it still cut out (with the cap on) although it was only for a REALLY quick second.......now....after all this i decided to test the same thing with an ext rx pack and guess what?...no more power loss.....AT ALL!!!....but i definitely do not want to drive aroudn with 4 AA batteries strapped to the chassis...lol.....ah well....i'm gonna try a different rx just to further single out the BEC as being the issue........simplechamp, see if the mmp BEC stalls out with the cap on doing the full lock/throttle punch test.... Hey Bernie/Patrick/Thomas/Joe...any input on this problem????

simplechamp · 05.13.2010, 05:01 AM

I am taking my buggy out for it's first runs today, so I'll see what happens with the BEC and receiver. During my bench testing the cap seemed to fix the issue, but like you showed that doesn't mean it will fix the problem when actually running. If it runs fine tomorrow I'll hold off on sending it in, but if it still has intermittent issues with the receiver powering down I will send it in. I know I could use an external CC BEC, but really shouldn't have to do that when the controller is brand new and has an adjustable voltage switching BEC built-in.

hootie7159 · 05.13.2010, 06:00 PM

another update...i bought and installed a brand new airtronics 192oz/in servo and the BEC issue was still present WITHOUT the cap added to the rx....hmmm...so it's definitely NOT the servo...the tx/rx setup isn't an issue B/C it runs fine in my friends slash 4x4 running his own mmp.....i guess i'll wait until my havoc pro gets back from warranty work before i send in my mmp.... :( but it's working ok for now with a cap added...

simplechamp · 05.13.2010, 06:32 PM

Thomas replied to my email today and said it does sound like the BEC. He asked for a few more details and I just replied, so we'll see what he says. He also mentioned adding the capacitor.

hootie7159 · 05.13.2010, 06:48 PM

hmm....so in order for the mmp to work right we need to add a cap?....well that sucks....LMK what he says about whether or not we should send it in...